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RQCM OPERATION AND SERVICE MANUAL

1. 8 2 8 3 GROUNDING CONSIDERATION 0 8 3 6 3 1 VOLTAGE MEASUREMENT GROUNDING 8 3 8 3 2 TEMPERATURE MEASUREMENT 22 2 00 000000 eene 8 3 9 VO CARD OPTIONAD emm 9 1 10 TROUBLESHOOTING 10 1 11 LOSA AM EL 11 1 12 REFERENCES 4222 0 00 12 1 FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU Table of Figures RE 1 CRYSTAL FACE MATING CONNECTOR csecssscsecsessssseceeeceesesssssceeececsenssaeceeececsenssaeceeececeensaasaeeeeeees 3 3 RE 2 CRYSTAL CHANNEL DESCRIPTION 3 4 RE 3 CAPACITANCE DJUSTMENTS u cas oar ee vo e eund 3 6 RE 4 TYPICAL CONNECTIONS FOR AN ELECTROCHEMICAL QCM EXPERIMENT 3 8 RE 5 TYPICAL VOLTAMMOGRAM PLOT OBTAINED USING THE 3 9 RE 6 RQCM FRONT dieit ccce tei e edo e ete Pe tea eere 3 12 RE 7 RQCM REAR PANEL viii 3 13 RE 8 INFICON 1 INCH DIAMETER CRYSTALS ELECTRODE 4 2 RE 9 INFICON 1 CRYSTAL AS SEEN FROM THE FRONT SIDE eese enne 4 2 RE 10 FREQUENCY VS TEMPE
2. Part Number Description 172205 CHT 100 Crystal Holder Teflon amp SMB Connector 173205 CHC 100 Crystal Holder CPVC BNC Connector 184204 CHK 100 Crystal Holder Kynar SMB Connector 184208 FC 550 Flow Cell 603211 DB25S to Terminal Strip for Passive I O Card 603212 DB37S to Terminal Strip for Data Acquisition Card 603216 2 Cable SMB Plug SMB Plug 2 length RG174A U coax 888023 Adapter BNC Male to SMB Jack 803081 Power Cord 803312 Capacitance Tuning Tool 885072 2 5 mm Male Connector For Crystal Face Refer to INFICON Price List for more accessories and other products 1 4 OPTIONAL CARDS Part Number Description 603208 Crystal Measurement Card 3 8 to 6 MHz 603208 2 Crystal Measurement Card 5 1 to 10 MHz 603209 Data Acquisition Card 603210 Passive I O Card GENERAL DESCRIPTION 1 5 RESEARCH QUARTZ CRYSTAL MICROBALANCE 2 GETTING STARTED 2 1 UNPACKING Y our was released to the carrier in good condition and properly packed It is essential to all concerned that the contents of the shipment be carefully examined when unpacked to assure that no damage occurred in transit Check the material received against the packing list to be certain that all elements are accounted for Basic items included with your RQCM are 1 RQCM Unit 1 Operation and Service Manual 1 Power cord 1 Capacitance Adjustment Tool 1 per Crystal Channel 1 2 5 m
3. 3 9 3 9 3 FOR OPERATION IN 3 9 3 9 3 1 Operate at or Near The Crystal s Turn Around Point 3 10 3 9 3 2 Control The Temperature ooconnccicnnoonconnnonconnconconncon ccoo 3 10 3 9 3 3 Keep the Test Chamber 3 10 3934 Keep a Constant Gas Flow 3 10 3 9 4 FOR OPERATION IN LIQUIDS esses eene eene enne enne steer enne 3 10 3 9 4 1 Degas The Sample Liquid 3 10 3 9 4 2 Wait For Mechanical Disturbances To Stabilize sss 3 10 3 9 4 3 Wait For The Temperature To Stabilize sss 3 10 3944 Prepare Your Solutions 3 11 3 0 4 5 Avoid Using Mireia RR 3 11 3 9 5 FOR OPERATION WITH THE FC 550 FLOW 3 11 3 9 5 1 Avoid Excessive Differential Pressure sess 3 11 3 9 5 2 Keep a Constant Line 3 11 3 9 5 3 Allow Ample Time For the Crystal To Come to Equilibrium 3 11 4 CRYSTALS HOLDERS AND FLOW CELL 4 1 4 1 1 INCH DIAMETER 5 5 4 1 4
4. 5 17 RE 26 FREQUENCY ERROR DUE TO IMPERFECT CAPACITANCE CANCELLATION 5 19 RE 27 CRYSTAL POWER DISSIPATION VS CRYSTAL RESISTANCE ccce eene 5 20 RE 28 095 DTE REAR PANEL RS 232 SOCKET CONNECTOR 7 2 RE 20 IEEE 488 CONNECTOR E E exes UP T ee uet oven rive eeu 7 3 RE 30 DB25P DATA ACQUISITION REAR PANEL 2 1 00 050 0 110000 000000000000000202001 8 1 RE 31 REAR PANEL T THERMOCOUPLE CONNECTOR ennemi 8 2 RE 32 DB73P I O REAR PANEL 9 1 vii viii List of Tables TABLE 5 1 MATERIAL DENSITY AND ACOUSTIC IMPEDANCE VALUE cccococonononononononononononononononononononononononnnos 5 4 TABLE 7 1 D9 REAR PANEL RS 232 RS 485 CONNECTOR PIN ASSIGNMENTS eere ener eren 7 2 TABLE 7 2 IEEE 488 PIN ASSIGNMENTS 7 4 TABLE 8 1 DB25P DATA ACQUISION REAR PANEL CONNECTOR PIN 8 1 TABLE 8 2 INPUT VOLTAGE RESOLUTION 8 1 TABLE 9 1 DB37P I O REAR PANEL CONNECTOR PIN ASSIGNMENTS 9 1 RESEARCH QUARTZ CRYSTAL MICROBALANCE 1 GENERAL DESCRIPTION
5. RESEARCH QUARTZ CRYSTAL MICROBALANCE 4 3 CRYSTAL HOLDERS Figure 12 shows a INFICON CHC 100 Crystal Holder without a crystal the crystal retainer or the retainer cover It has a cavity for a 1 inch diameter crystal Inside the cavity there are two Pogo pins providing connections to the crystals front and rear electrodes Note the locations of the Pogo pins These pins are internally connected to the BNC connector Jack for CHT 100 and CHK 100 holders via an internal coaxial cable INDEX PIN POGO PIN CONNECTS TO BNC CENTER POGO PIN CONNECTS TO BNC HOUSING FEMALE BNC OR SMB JACK Figure 12 CHC 100 Crystal Holder 4 3 1 HOW TO INSTALL A CRYSTAL IN A INFICON CRYSTAL HOLDER 1 Identify the Front and Rear Sides of the crystal See Section 4 1 2 Clean amp Dry the Crystal Holder cavity then insert the Crystal with the Front Side Sensing Electrode exposed The Wrap Around Extended Electrode MUST be in the 60 region as in Figure 13 below o CRYSTALS HOLDERS AND FLOW CELL RQCM RESEARCH QUARTZ CRYSTAL MICROBALANCE 52 60 N HOLDER CRYSTAL Figure 13 Crystal Installation 3 Place the Retainer Ring over the Crystal with the Notch mating to the Index Pin 4 Mount and turn the Retainer Cover approximately 1 4 turn Then with a gloved finger or cotton swab gently press the Retainer Ring down at the Notch to make sure that it stays mated to the Index Pin Finish tightening the Cover
6. If the capacitance is over compensated it lags the voltage a phase angle of minus 90 degrees The Yellow Sweep LED is used to determine whether the crystal capacitance is over compensated or under compensated The Sweep LED flashes whenever the crystal capacitance in under compensated If the Sweep LED is not flashing turn the fine adjustment counterclockwise until it begins to flash then back up until it just stops If it is flashing turn the fine adjustment clockwise until it just stops flashing This is a very fine adjustment Go back and forth until you are sure you are right on the edge The sensitivity of the fine adjustment is approximately 0 05 pfd per degree In situations where the crystal resistance is very high over 1 a net capacitance of over 0 5 pfd can result in a significant frequency error so try to get this adjustment to within a couple of degrees Remember to keep the Reset switch depressed while making this adjustment 3 5 ADJUSTING CAPACITANCE CANCELLATION TRIMMER amp SWITCH Setting up the capacitance cancellation is fairly straightforward The thing to remember is that there are two adjustments a course rotary switch and a fine capacitor trimmer with the total compensation capacitance being the sum of the two The trim capacitor has no stops so it s not obvious when it is at its minimum or its maximum The fine adjustment capacitor has circular rotor plates that mesh into fixed stator plates The capaci
7. 12 SPECIFICATIONS eite siete tiere dee ere dein 1 3 1 2 1 CRYSTAL MEASUREMENT nicca 1 3 1 2 2 DATA ACQUISITION ANALOG CARD OPTIONAL 1 3 1221 Analog Inputs 1 3 12 221 Thermocouple at ss 1 4 1 2 2 3 RED Input tele 1 4 1224 Thermistor reet etd lee er lebe e edit 1 4 1 2 3 WO CARD OPTIONAE xit tete eee e e e 1 4 1 2 4 COMMUNICATIONS ote dte E RU GI iei 1 4 1 2 5 FRONT PANEL INDICATORS esses eee 1 4 1 2 6 POWER 5 1 4 1 2 7 PHYSICA teu web it 1 4 13 ACCESSORIES E 1 5 LA OPTIONAL CARDS cia att pee 1 5 2 GETTING STARTED aun iia 2 1 2 JUNPAGKING en io 2 1 22 SAFETY PRECAUTION 2 1 2 2 1 LINE VOLTAGE ete eere rU 2 1 2 2 2 aceite RE 2 1 2 2 3 LINE FUSES RES 2 1 23 SYSTEM CHECKOUT incerti nenn 2 1 2 3 1 CRYSTAL MEASUREMENTS 2 2 23 11 NT 2 2 23 12 A A ER ERES EET NER 2 3 ellc uec I 3 1 3 1 GENERAL DESCRIPTION OF THE CRYSTAL MEASUREMENT 3 1 32 UNDERSTANDING AND SETTING UP A CRYSTAL MEASUREMENT
8. 3 Buttry Daniel and Ward Michael Measurement of Interfacial Processes at electrode surfaces with the EQCM Chem Rev 92 6 1992 1355 31 o Melroy Kanazawa J G Gordon II and D Buttry Direct Determination of the Mass of an Underpotentially Deposited Monolayer of Lead on Gold Langmuir 2 1986 697 Mark R Deakin and Owen Melroy Underpotential Metal Deposition on Au monitored in situ with a Quartz Microbalance J Electroanal Chem 239 1988 321 33 Masahiro Seo Masaki Aomi and Kengo Yoshida A combined Piezoelectric and EQCM study of Underpotential Deposition of Silver on Gold Electrodes Electrochimica Acta 39 8 9 1994 1039 12 2 REFERENCES RESEARCH QUARTZ CRYSTAL MICROBALANCE Y oungran Lim and Euijin Hwang An Electrochemical QCM study of Oxygen reduction during the Underpotential Deposition of Lead on a Gold Electrode Bull Korean Chem Soc 17 12 1996 1091 34 Storri S Santoni T Mascini M A piezoelectric biosensor for DNA hybridization detection Anal Lett 31 11 1998 1795 id Jope Dirk Sell Joachim Pickering Howard Weil Konrad G Application of a Quartz Crystal Microbalance to the Study of Copper Corrosion in Acid Solution Inhibited by Triazole Iodide Protective Films J Electrochem Soc 142 34881 2170 2172 5 Jiang Xiang Chun Seo Masahiro Sato Norio Piezoelectric Detection of Oxide Formation and Reduction on Platinum Ele
9. Pin A lot used x Output lot used N lot used TS Input TS Output RTS Output Not used Table 7 1 D9 Rear Panel RS 232 RS 485 Connector Pin Assignments 7 6 RS 485 SERIAL INTERFACE The optional RS 485 serial interface ofthe ROCM allows connection of up to 32 separate devices equipped with RS 485 The RS 485 serial interface is also ideal in electrically noisy environments and in applications where long cables are required The RS 485 port of the RQCM is the same D9P connector on the rear panel used for RS 232 The pin layout is shown in Figure 28 and Table 7 1lists the pin signal assignments including a definition of whether the signal is an input or an output of the RQCM The RQCM s RS 485 port is automatically set up to operate with the following specifications 19200 Baud 8 Bit data No Parity 1 Stop bit 7 2 COMPUTER INTERFACE RESEARCH QUARTZ CRYSTAL MICROBALANCE 7 7 EEE 488 PARALLEL INTERFACE The optional IEEE 488 interface provides the RQCM with the ability to communicate with computers and other devices over a standard IEEE 488 interface bus The IEEE 488 interface also known as GPIB or HPIB provides an eight bit parallel asynchronous interface between up to 15 individual devices on the same bus This means that one computer equipped with an IEEE 488 interface card can communicate with up to 14 RQCMs or other devices The pin layout of the IEEE 488 port is shown in Figure 29 and Table 7 2 lists
10. inert or vacuum atmosphere within its temperature range n Figure 31 Rear Panel Type T Thermocouple Connector 8 2 DATA ACQUISITION CARD OPTIONAL RESEARCH QUARTZ CRYSTAL MICROBALANCE 8 3 GROUNDING CONSIDERATION Proper grounding and shield termination is mandatory for accurate measurements 8 3 1 VOLTAGE MEASUREMENT GROUNDING If the voltage to be measured is returned to earth ground within the common mode voltage range at its source neither the Input nor the Common lead should be grounded at the voltage measurement point since the RQCM will return to earth ground through its power cord The shield for the input leads must only be terminated at the Data Acquisition Card connector If the voltage to be measured is isolated from earth ground the shield or its drain wire should be connected to the common side of the voltage to be measured at the voltage source as well as at the shield terminal on the Data Acquisition Card 8 3 2 TEMPERATURE MEASUREMENT GROUNDING All three temperature sensors must be of the isolated or ungrounded type Sensor lead wire shields should be terminated at the ROCM Data Acquisition Card connector only The measured device should be connected to earth ground Exposed junction probes should not be used to measure the temperature in a conductive media like water DATA ACQUISITION CARD OPTIONAL 8 3 RESEARCH QUARTZ CRYSTAL MICROBALANCE 9 I O CARD OPTIONAL The RQ
11. respectively Note that some of the discrepancy in the resistance curve could arise from an error in estimating the active electrode area The RQCM utilizes the PLO technology which allows the sensor crystal to operate under heavy viscous loading INFICON Crystal Holders support operation in gas and liquid environments and provide single electrode exposure to liquids as required for compatibility with electrochemical QCM measurements The RQCM will maintain oscillation up to a series resonance resistance of about 5 It will support crystal operation in highly viscous solutions up to 88 weight percentage of glycerol The computer software provides a friendly interface for setting up the to log and graph data collected from the sensor crystal such as frequency change resistance change mass etc Frequency Change vs Wt Glycerol Wt Glycerol 0 10 20 30 40 50 60 70 80 90 100 0 Theory m RQCM 2000 E 3000 S 4000 gt 5 5000 5 6000 S 7000 8000 E 9000 10000 Figure 14 Frequency Change vs Wt Glycerol THEORY OF OPERATION 5 7 RESEARCH QUARTZ CRYSTAL MICROBALANCE Resistance Change vs Wt Glycerol 5000 4000 3000 2000 Delta Resistance ohms 1000 Wt Glycerol Figure 15 Resi
12. 7 2 RECOMMENDED MINIMUM COMPUTER CONFIGURATION e Pentium 500 MHz PC 24 MB of RAM This is in addition to the Operating System requirements 35 MB of hard disk space Additional free hard disk space 5 required for data storage e CD ROM drive e Microsoft Windows 9x ME NT4 SP3 or later 2000 XP 7 3 SOFTWARE INSTALLATION Follow the instruction below to install the software on the computer 1 Insert the ROCM Software CD into the CD ROM drive 2 If your system supports the auto run feature installation begins automatically 3 If your system does not support the auto run feature click Start Run then enter setup where X is the CD ROM s drive letter 4 Follow the instructions in the windows as they appear 7 4 CREATING YOUR OWN SOFTWARE Although the RQCM includes a comprehensive Windows based interface program some users may find it necessary to create their own interface program This section describes the various computer interfaces and the protocol of the RQCM There are three types of computer interfaces offered The RQCM comes standard with an RS 232 serial interface Both RS 485 and IEEE 488 interfaces are available as options 7 5 RS 232 SERIAL INTERFACE The standard RS 232 serial interface of the allows one RQCM to be connected to any other device with an RS 232 serial interface The RS 232 interface port is the D9P connector on the rear panel of the RQCM The pin layout is shown in Figure
13. CHANNEL 3 2 33 FRONT PANEL DESCRIPTION Qo 3 2 3 3 1 LOCKINDIGCATOR sd Ense edite a Se 3 2 3 3 2 UNLOCK INDICATOR 3 2 3 3 3 SWEEPINDICATO R aee d al aan denied 3 2 3 3 4 RESET SWITCH stad GIC diu M Ed 3 2 3 3 5 CRYSTAL CONNECTOR 5 sa o eie Ede e I dre 3 2 3 3 6 CRYSTAL FACE eene eene 3 2 3 3 6 1 Crystal Face Mating Connector sss eene nennen nennen nnne nnns 3 3 3 3 7 FINE AND COURSE CAPACITANCE ADJUSTMENTS cesses 3 3 34 ADJUSTING THE 2 3 5 35 ADJUSTING CAPACITANCE CANCELLATION TRIMMER amp SWITCH 3 5 3 5 1 AS A GENERAL RULE uis en a Deep date el sek 3 6 36 WORKING WITH VERY LOW 5 2 1 4004 0 00000000100600000000000000 3 3 7 3 7 NORMAL OPERATION nun sen nenne Bin innen Peer t tue ens 3 7 38 HOOKUP FOR ELECTROCHEMICAL EXPERIMENTS eese 3 7 3 9 OPERATION GUIDELINES eren 3 9 3 9 1 ALLOW THE WARM UP 3 9 3 9 2 ISOLATE THE FROM TEMPERATURE CHANGE
14. act as adsorption sites on silica or glass stationary chromatographic phases with silane coupling agents to give the inactive O SiR3 grouping Silanization can neutralize surface charges thus eliminating non specific binding Redox An oxidation reduction reaction the term redox is obtained from the first few letters of reduction and oxidation Mole That amount of a substance containing the same number of units as 12 g of carbon 12 Molar mass The mass of a mole of substance the same as molecular weight for molecular substances Symbol for angstrom a unit of length equal to 107 meter GLOSSARY 11 3 RESEARCH QUARTZ CRYSTAL MICROBALANCE 12 REFERENCES Martin Stephen et al Effect of Surface Roughness on the Response of Thickness Shear Mode Resonators in Liquids Anal Chem 65 1993 2910 Sullivan C K and Guilbault G G Commercial Quartz Crystal Microbalances theory and applications Biosensors and Bioelectronics 14 1999 663 670 Sauerbrey G 7 Phys 155 1959 206 Gabrielli C et al Calibration of the Electrochemical Quartz Crystal Microbalance J Electrochem Soc 139 9 1991 2657 7 Denison D R Linearity of Heavily Loaded Quartz Crystal Microbalance J Vac Sci Technol 10 1973 126 Behrndt H Long Term Operation of Crystal Oscillators in Thin Film Deposition 7 Vac Sci Technol 8 5 1971 622 7 Lu Chih shun Ma
15. design your own crystal or holder If you have purchased a INFICON crystal holder and cable the installation is simple Follow the instructions below If you plan to build your own crystal or holder or cable see Section 4 3 2 4 1 1 INCH DIAMETER CRYSTALS IINFICON pioneered the standard AT cut 5 MHz 1 inch diameter crystals for use in liquid applications The AT cut quartz is chosen for its superior mechanical and piezoelectric properties and the angle of cut can be adjusted to obtain a zero temperature coefficient at a desired operating temperature The 1 inch diameter was chosen to allow enough distance between the active area of the crystal and the mounting o ring This improves the overall stability of the crystal by reducing the frequency changes due to mounting stress 4115 ELECTRODE CONFIGURATION Figure 8 below shows INFICON s 1 crystal electrode patterns The left figure shows the Y inch diameter front electrode also called sensing electrode with an extended electrode that wraps around the edge of the crystal and extends into a semicircle shown in the top half of the right figure The lower half of the right figure shows the 4 inch diameter rear electrode also called contact electrode This configuration enables both electrical contacts to be made on the backside of the crystal allowing measurement in conductive liquids The oversized front electrode inch in diameter as oppose to the 1 4 inch diameter rear electr
16. fine trimmer clockwise until it just stops flashing Go back and forth a few times to get a feel for the point where the Sweep LED just stops flashing Release the Reset button and the Sweep LED should begin to flash again Install a crystal The PLO should lock Even so press and hold the Reset button and again adjust the fine trimmer to the point where the flashing just stops The capacitance cancellation adjustment is now perfect Remember to check this adjustment whenever the crystal s environment changes If you could not find the proper zero capacitance point using the fine trimmer alone then the coarse rotary switch needs to be adjusted Follow the instructions below to set the coarse rotary switch First adjust the fine trimmer so that it is 50 meshed and the rotor plates are below the shaft You can see these plates through the oversize adjustment hole See Figure 3 Next connect a cable and crystal holder and the crystal if you haven t already done so STATOR PLATES SILVER FINE ADJUSTMENT TRIMMER ROTOR PLATES GOLD 50 MESH COARSE ADJUSTMENT ROTARY SWITCH Figure 3 Capacitance Adjustments Set the course rotary switch to its minimum Depress the Reset button and observe the yellow Sweep LED It should be flashing very fast indicating the capacitance is grossly under compensated Now rotate the course switch clockwise one step at a time At each stop observe the yellow Sweep LED at some point it will ce
17. frequency reading when the crystal or the holder or the cable is being touched Same as above The crystal measurement is reacting to the change in total capacitance when the setup 1s being touched Avoid contact with the hookup during an experiment This is especially important if the crystal is a low Q crystal Frequency reading is unstable or drifting Temperature of the crystal is changing An AT cut crystal frequency may drift as much as 10 Hz C Control temperature of the test environment Humidity level on the crystal is changing Moisture being absorbed or exuded from the crystal surface Control humidity of the test environment TROUBLESHOOTING GUIDE 10 1 RESEARCH QUARTZ CRYSTAL MICROBALANCE Unbalanced or damaged coaxial cable Check cable for any signs of damage such as broken shield Replace cable Unit shows Lock with no crystal holder and cable connected to the crystal channel The capacitance was probably adjusted with the crystal holder and cable combined With everything removed the Lock light just means that the capacitance is now grossly out of adjustment This is normal Re connect the crystal holder and cable Unit shows Lock but the frequency reading is at its lowest and the resistance reading 1s about 1 ohm An electrical short across the crystal input Check the cable holder and the crystal fo
18. of loaded crystal in seconds Although the above equation still involves a number of simplifying assumptions its ability to accurately predict the film thickness of most commonly deposited materials has been demonstrated The RQCM uses this equation to calculate film thickness The basic measurement is period which can be thought of as a measurement of equivalent quartz mass The actual film mass on the crystal is then found by applying the acoustic impedance correction factor When the mass is zeroed using the the initial equivalent quartz mass and the initial corrected film mass are stored For each subsequent measurement the new corrected total film mass is calculated and the film mass deposited since the thickness was zeroed is determined by subtracting the initial corrected film mass from the total corrected film mass The film thickness on the crystal is calculated by dividing by the film mass by the material density The Lu and Lewis equation is generally considered to be a good match to the experimental results for frequency changes up to 40 relative to the unloaded crystal Keep in mind that the Z match equation strictly applies to elastic lossless films Films which behave viscoelastically such as some organic polymer films with large thickness or viscosity will exhibit significant deviations from both Equation 3 and Equation 6 THEORY OF OPERATION 5 3 RESEARCH QUARTZ CRYSTAL MICROBALANCE Table 5 1 Mat
19. ohm crystal Combining these two errors we can get an idea of the magnitude of the frequency error caused by imperfect capacitance cancellation For 10 crystal a one picofarad capacitance imbalance results in a 0 018 degree phase error and a 0 0067 Hz frequency error For a 100 crystal the phase error is 0 18 degrees and the frequency error is 0 67 Hz Fora 1000 Q crystal the phase error is 1 8 degrees and the frequency error is 67 Hz For a 5000 crystal the phase error is 9 degrees and the frequency error is 1 635 Hz A two picofarad capacitance imbalance will result in approximately twice the above error Frequency Error vs Crystal Resistance 100000 000 Y 10000 000 1000 000 100 000 10 000 Freq Error due to a 5 pfd Frequency Error Hz Freq Error due to a 2 pfd ranaritanra Freg Error due to a 1 pfd capacitance 11411112 Crystal Resistance ohm Figure 26 Frequency Error Due to Imperfect Capacitance Cancellation 5 9 CALCULATING CRYSTAL POWER Crystal power can be calculated as follows Crystal power Pery i Ray Crystal current i Vo Rs Ray Hence Pay 1 Rey Voc Rs Rey Rory Where THEORY OF OPERATION 5 19 RESEARCH QUAR
20. range 0 to 50 C Operating temperature range for stated stability 20 10 C Controls Reset Switch Capacitance Adjustment Trimmer Course and Fine Indicators Green Lock LED Yellow Sweep Rate LED Crystal Face Isolation Transformer 200 VDC maximum 1 2 2 DATA ACQUISITION ANALOG CARD OPTIONAL Except where noted All specifications 25 C All specifications are within 90 days of calibration 1 2 2 1 Analog Inputs 200 200V 70 dB up io 200 Hz Differential input impedance GENERAL DESCRIPTION 1 3 RESEARCH QUARTZ CRYSTAL MICROBALANCE 1 2 2 2 Thermocouple Input Type T thermocouple 010 371 C Accuracy 2 C sensor error 1 2 2 3 RTD Input 100 0 Thin film platinum 0 to 600 C 1 2 2 4 Thermistor Input E EE 100 KO 0 to 150 C 1 2 3 CARD OPTIONAL Number of Discrete Inputs 8 ground true 4 7K pulled up to 5V Number of Discrete Outputs 8 SPST relays 120VA 2 A max 1 24 COMMUNICATIONS RS 232 serial port standard RS 485 serial port optional IEEE 488 optional 1 2 5 FRONT PANEL INDICATORS Communication Status LED s System Ready LED 1 2 6 POWER REQUIREMENTS 100 200 220 240 VAC a 50 60Hz 25 W 1 2 7 PHYSICAL Size including feet x 13 W x 9 D Weight 7 lbs Shipping Weight 10 lbs 1 4 GENERAL DESCRIPTION RESEARCH QUARTZ CRYSTAL MICROBALANCE 1 3 ACCESSORIES
21. so important with high resistance crystals The first is that to a first approximation the frequency error resulting from a given phase error is proportional to the bandwidth of the crystal The bandwidth of the crystal is proportional to the crystal s resistance ten ohm crystal might typically have a bandwidth of 42 Hz while a one thousand ohm crystal will have a bandwidth of 4 200 Hz A five thousand ohm crystal will have a bandwidth of 21 000 Hz Since the frequency error for a given phase error is proportional to the bandwidth a phase error that would result in a 0 5 Hz frequency error in a ten ohm crystal will cause a 50 Hz error in a one thousand ohm crystal and 250 Hz error in a five thousand ohm crystal The second reason is that the effective phase error caused by a non zero net quadrature current is inversely proportional to the real current which is inversely proportional to the crystal resistance In other words the effective phase error is proportional to the crystal resistance For instance a net unbalance of 1 pfd leads to an effective phase error of 0 02 degrees for a ten ohm crystal but it leads to a 2 degree error for a one thousand ohm crystal and a 10 degree error for a five thousand ohm crystal Examples A ten ohm 5 MHz crystal will have a Q Quality Factor of about 120 000 The bandwidth is equal to the crystal frequency divided by Q Thus the bandwidth of this crystal would be about 42 Hz To a first approximat
22. terminal The sleeve terminal is not used You can disregard 1t or break it off Figure 1 Crystal Face Mating Connector 3 3 7 FINE AND COURSE CAPACITANCE ADJUSTMENTS The Fine and Course capacitance adjustments are used together to cancel out the unwanted static capacitance of the crystal the crystal holder and the connecting cable Refer to Section 3 4 for procedure on the proper adjustment OPERATION 3 3 RESEARCH QUARTZ CRYSTAL MICROBALANCE 300419313 ONDRIOM TVLSAUO IHL SIV OL ANIWNYASNI 7IVOIWSHOOMIO3T3 NY NOLLOINNO9 YOLIINNO9 TVLSAYO N3349 YOLVOIGNI HOLVOIGNI ADO NN SI 1 16 SSAVOIGNI ONIHSV14 MOTISA YO LVOIIONI 3 1V d33MS AONSNDAYS 30V4 IVLSAYO 3dOu403713 JHL OL SLOANNOO SNISNOH YO LOSNNOO JHL ANY 300H19313 YV3Y JHA OL SL1OSNNOO Nid 1 JHL IVLSAMO JHL OL SNOLLO3NNOO HOLO3NNOO TV1SAMHO GONV LIOVdVO LNO ANNA OL Gasn 3ONV LIOVdVO 3Sunoo TIVWS LNO ANNL OL G3sn 3ONV LIOVdVO CNOLLVTISONVO ONLLSNFAV 5 39 ASNW NOLLNG SIHA 7HOLVOIGNI X907 IHL SNYNL INNNININ SLI AONINOTUS 5 NIHM NOLLNG 13534 MalA WILYVd WIOU 39VJ3 TV1LSAUD 3901 AJO IN
23. the Sweep LED just ceases to flash With very low Q crystals the PLO may not lock upon release of the Reset button The Unlock LED will be on and the Sweep LED will be flashing This is normal Even so it may be possible to lock on the crystal by slowly adjusting the fine capacitance clockwise until the Sweep LED again ceases to flash Lock is evidenced by the Lock LED turning on or by a crystal resistance of less than 10 Once lock is achieved the true series resonant point can be found by adjusting the capacitance for minimum resistance value The limits of the crystal bandwidth can be determined by adjusting the capacitance and reading the maximum frequency and the minimum frequency just before the RQCM loses lock 3 7 NORMAL OPERATION The RQCM comes set up for operation with a INFICON cable and crystal holder Ifa INFICON cable and crystal holder is being used then no initial adjustments should be needed During normal operation with a crystal installed and connected to the oscillator the green Lock LED will be on and the frequency output will reflect the crystal resonance The red Unlock LED will be off If the Unlock LED is on the Sweep LED should slowly flash Continuous sweeping of the frequency range indicates that the crystal s resonant frequency is outside of the PLO s frequency range or the crystal s conductance is below the conductance threshold No flashing of the Sweep LED when the Unlock LED is on can mean one of two thi
24. the pin signal assignments including a definition of whether the signal is an input or an output of the ROCM The RS 232 serial port can still be used with IEEE 488 installed However since both interfaces use the same input and output message buffers they should not be used at the same time This will result in communication errors 13 24 m 1 2 Y Figure 29 IEEE 488 Connector DATA V O 1 2 2 AAA Eo ox Wa alo DO sn 5 End Or Identify 6 David 8 ata Not Accepted 9 Service Request EN 22 GN Logic GND COMPUTER INTERFACE 7 3 RESEARCH QUARTZ CRYSTAL MICROBALANCE Table 7 2 IEEE 488 Pin Assignments 7 8 PROTOCOL All communications between the computer and the RQCM are in the form of messages with the format Two byte header FFh FEh i e Chr 255 Chr 254 The header indicates the beginning of a message One byte device address 1 to 32 The device address byte defines the bus address of the instrument that sent or should receive the message The device address will range from 1 to 32 A message sent to a device address of zero will be received by all RQCMs except in the case of the IEEE 488 interface With this interface only the addressed device will receive the message One byte instruction code 0 to 6 Defines the code number
25. volt range and 1 hertz filter and the temperature inputs to Celsius computer would send Chr 255 Chr 254 Chr 1 Chr 2 Chr 6 Chr 0 Chr 0 Chr 0 Chr 0 Chr 0 Chr 7 Chr 240 4 Internal Command 5 Internal Command 6 Internal Command 7 Receive Relay Output Status Code 6 This instruction allows the computer to open or close the RQCM s relay outputs Each bit of the one byte command code in the message determines the status of one output If the bit is 1 then that output relay will close If the bit is 0 then that relay output will open Bit 0 relay 1 bit 1 relay 2 etc For example To instruct the RQCM to close relays 1 amp 2 and open all other relays the computer would send Chr 255 Chr 254 Chr 1 Chr 6 Chr 1 Chr 3 Chr 245 7 8 COMPUTER INTERFACE RESEARCH QUARTZ CRYSTAL MICROBALANCE 8 Internal Command 9 Set ROCM Interface Address Code 8 This instruction allows the computer to set interface address The RQCM s interface address allows for multiple instruments to share the same communications bus You can have multiple RQCM s on the same bus but each must have a unique interface address so the computer can communicate with each one individually The interface address can range from 1 to 32 All RQCM s are shipped with the interface address set to one For example set the RQCM s interface address to 2 the computer would send Chr 255
26. well mixed Ifthis 15 the case keep the stirrer rotating speed constant throughout the experiment 3 9 5 FOR OPERATION WITH THE FC 550 FLOW CELL The FC 550 is used in place of the Crystal Retainer Ring to create a flow chamber of 0 1 mL This setup can be used for either gas or liquid flow In both cases observe the following tips to avoid unwanted effects in the measurements 3 9 5 1 Avoid Excessive Differential Pressure The differential pressure from the front to the back of the crystal must be minimized to avoid frequency errors due to stress on the crystal and to avoid crystal breakage INFICON s 1 inch 5 MHz AT cut crystal will fracture at pressure differentials above 5 PSI 3 9 5 2 Keep a Constant Line Pressure Using a pumping system that minimizes pulsation and maintains a constant line pressure throughout the experiment A syringe pump is a good choice because it provides pulse less flow If a peristaltic pump is used then it is better to pull the liquid through the flow cell to reduce frequency fluctuations caused by pulsing Gravity flow is another good method for flowing fluid through the cell without the pulsation effects However the line pressure does change as the volume of the fluid reduces in the reservoir Care must be taken to maintain the volume in the reservoir 3 9 5 3 Allow Ample Time For the Crystal To Come to Equilibrium Expose the flow cell s chamber and the sensor crystal to the medium Wait for it to come
27. 000 4888 Stange T G et al STM and AFM Characterization of Polystyrene Spin coated onto Silicon Surfaces Langmuir 8 1992 920 5 Vig J R UV Ozone cleaning of surfaces A review in Surface contamination Genesis Detection and Control K L Mittal Ed Plenum Press NY 1979 Pages 235 253 16 Krozer A and Rodahl Michael X ray Photoemission spectroscopy study of UV ozone oxidation of Au under ultrahigh vacuum conditions J Vac Sci Technol A 15 3 1997 1704 REFERENCES 12 1 RESEARCH QUARTZ CRYSTAL MICROBALANCE 17 Prime K L Whitesides G M Science 252 1991 1164 Prime K L Whitesides G M J A Model System Using Self Assembled Monolayers Am Chem Soc 1993 v 115 10714 10721 18 Colorado Jr Ramon Villazana Ramon J and Lee T Randall Self Assembled Monolayers on Gold Generated from Aliphatic Dithiocarboxylic Acids Langmuir 14 1998 6337 6340 12 Duan Lili and Garrett Simon J Self Assembled Monolayers of 6 Phenyl n hexanethiol and 6 p Vinylphenyl n hexanethiol on Au 111 An Investigation of Structure Stability and Reactivity Langmuir 2001 17 2986 2994 E Hockberger et al Cellular engineering control of cell substrate interactions in Nanofabrication and Biosystems H C Hoch L W Jelinski and H G Craighead Eds Cambridge University press 1996 276 299 2 Buttry Daniel Applications of the QCM to Electroche
28. 1 Safety EN 61326 1 1997 A1 1998 A2 2001 Class A Emissions per Table 3 Immunity per Table A 1 Due to the classification of this product it is currently exempt from the RoHS directive October 1 2007 Duane H Wright Quality Assurance Manager ISS INFICON Inc ANY QUESTIONS RELATIVE TO THIS DECLARATION OR TO THE SAFETY OF INFICON S PRODUCTS SHOULD BE DIRECTED IN WRITING TO THE QUALITY ASSURANCE DEPARTMENT AT THE ABOVE ADDRESS 10 01 07 Warranty INFICON warrants the product to be free of functional defects in material and workmanship and that it will perform in accordance with its published specification for a period of twenty four 24 months The foregoing warranty is subject to the condition that the product be properly operated in accordance with instructions provided by INFICON or has not been subjected to improper installation or abuse misuse negligence accident corrosion or damage during shipment Purchaser s sole and exclusive remedy under the above warranty is limited to at INFICON s option repair or replacement of defective equipment or return to purchaser of the original purchase price Transportation charges must be prepaid and upon examination by INFICON the equipment must be found not to comply with the above warranty In the event that INFICON elects to refund the purchase price the equipment shall be the property of INFICON This warranty 5 in lieu of all other warranties expressed or impli
29. 1 1 ELECTRODE 4 1 4 12 GRYSTAT PARAM ETERS x a ia ee iian 4 2 4 1 3 CRYSTAL SURFACE FINISH dar repeto pee e teet e ege ep peces en 4 3 4 1 4 CRYSTAL ELECTRODE 4 3 4 1 5 CRYSTAL THICKNESS idonea et Se EE dei teres 4 3 4 1 6 MASS SENSITIVITY cont a b IRR UE 4 3 4 1 7 Oi mn meson Ado Ca ete map Mela c em 4 4 4 1 8 CRYSTAL LIFE EXPECTANCY nn cnn nono 4 4 4 1 9 TEMPERATURE COEFFICIENT siirsi 4 5 4 2 CRYSTAL CARE AND HANDLING onenean eee a 4 7 4 2 1 CRYSTAL CLEANING sone UE EE e RP 4 8 4 2 1 1 General Cleaning cion ia in 4 8 4 2 1 2 Organic hydrocarbon 1 2 2 0020002000000000000000000000000000000040000 4 8 4 2 1 3 Biomaterials lipids proteins and similar biomolecules esses 4 8 4 2 1 4 Lipid vesicles on SiO surfaces sse ene 4 8 4 2 5 iii 4 8 4 2 6 Polymer Removal conil POT ERSTER 4 8 4 2 2 ELECTRODE SURFACE MODIFICATIONS 4 9 42 21 SPIN COATING 4 9 4222 SELF ASSEMBLED MONOLAYERS 4 9 4223 PHYSICAL VACUUM DEPOSITION PVD sees 4 9 43 CRYSTAL HOLDERS eicere tere e I eed tpe R
30. 2 ELECTRODE SURFACE MODIFICATIONS A QCM will response to anything that has mass Thus it is imperative for the QCM user to develop a condition where the QCM will only responsed to the substance of interest This usually involves a chemically or biologically sensitive layer applied to the surface of the crystal INFICON offers a wide variety of standard electrode materials for you to choose from Contact us if you don t see one that fits your needs If you choose to do your own crystal surface modification use the following guidelines 4 2 2 1 SPIN COATING Thin films nm to microns of polymers and other materials can be applied by spin coating 4 Polystyrene is a common material spin coated on QCM sensor crystals UV Ozone treatment can be used to change the hydrophobicity of organic polymeric coatings 4 2 2 2 SELF ASSEMBLED MONOLAYERS SAM 17 18 19 Self assembling monolayers can be laid down on gold or silver surface by thiolization or on SiO by silanization to control surface properties 4 2 2 3 PHYSICAL VACUUM DEPOSITION PVD Thin films of metals or metal oxides can be applied by sputtering or thermal evaporation in a vacuum chamber To ensure quality and reproducible films careful attention to cleanliness must be observed both in the vacuum chamber and in the preparation of the crystals prior to coating INFICON is an expert in PVD Consult us for any special needs CRYSTALS HOLDERS AND FLOW CELL 4 9
31. 28 and Table 7 1 lists the pin signal assignments including a definition of whether the signal is an input or an output of the RQCM COMPUTER INTERFACE 7 1 RESEARCH QUARTZ CRYSTAL MICROBALANCE The RQCM acts as DTE and accordingly the 9 pin connector has plug pins It can be used with a DCE or a DTE host cable connection providing the sense of the RxD TxD data lines and the control lines is observed Pin 2 TxD transmits data from the RQCM to the host pin 3 RxD receives data from the host Pin 7 CTS is a control output signal and pin 8 RTS isa control input signal In this implementation pin 7 CTS means what is says namely this is an output control line and when the RQCM asserts this control line true the host can transmit to the RQCM On the other hand pin 8 RTS is not quite what it may seem because this is a signal input to the ROCM and it is intended that the host should assert this line true only when the RQCM is allowed to transmit data to the host The RQCM does not generate an RTS request to send as such for the host PC so the host should assert pin 8 true whenever the RQCM is allowed to transmit to the host without being asked to do so The RQCM s RS 232 port is automatically set up to operate with the following specifications 19200 Baud 8 Bit data No Parity 1 Stop bit 12 34 5 6 7 89 Figure 28 095 DTE RS 232 socket connector
32. ATION The Crystal face is galvanically transformer isolated from earth ground The Crystal Face connection allows the crystal face electrode to be easily connected to an external voltage or current source such as a potentiostat 1 1 8 FULLY INTERGATED COMPUTER SOFTWARE Computer software is included with each RQCM allowing the user to set up graph and log frequency and resistance of the crystals from a computer It also allows the setup graphing and logging of temperature and analog data if the hardware is installed 1 1 9 INPUTS AND OUTPUTS CAPABILITY As an option the RQCM can be outfitted with an I O Card This card provides eight remote discrete inputs and eight relay outputs These I O s can be used to monitor or control external instruments and peripheral devices 1 1 10 DATA ACQUISITION To support the simultaneous logging and display of additional analog information such as voltage current or temperature the RQCM can be outfitted with an optional Data Acquisition Card This card supports three types of temperature sensors RTD Thermocouple and Thermistor as well as five scalable analog inputs 1 2 GENERAL DESCRIPTION RESEARCH QUARTZ CRYSTAL MICROBALANCE 1 2 SPECIFICATIONS 1 2 1 CRYSTAL MEASUREMENT 40 to 200 pfd Frequency error vs phase error and crystal Q Q 100 000 0 087 ppm per degree Q 10 000 0 87 ppm per degree Q 1 000 8 7 ppm per degree From 0 5 to 20 updates sec Operating temperature
33. CH QUARTZ CRYSTAL MICROBALANCE Freq Change vs Temp INFICON AT cut for 25C 275 250 225 200 175 150 125 100 73 50 25 Delta Frequency Hz 25 0 10 20 30 40 50 60 70 80 90 100 110 120 Temperature Figure 11 Frequency vs Temperature of INFICON 1 AT Cut Crystal for 25 4 2 CRYSTAL CARE AND HANDLING It is essential that a sensor crystal is clean and free of foreign matter that may react with the experiment inducing errors in the measurements The following guidelines are recommended for general handling of the sensor crystals Keep the crystals in a clean environment Store them in their original package until use Never handle the crystals with bare hands Always use plastic tweezers around the edge of the crystal during handling Do not touch the center of a sensor crystal as any oil dirt dust or scratches will quickly degrade the quality of the crystal When using a chemical agent to clean the crystal ensure that the crystal electrode material s will not be damaged by the chemical Never use cleaner that will etch the quartz surface Always rinse with deionized water or another appropriate pure liquid before drying the crystal Always use a flow of dry oil free non reactive gas e g filtered nitrogen to blow dry the crystal It 15 better to chase liquid off the crystal than to let it evaporate off the crystal Never wipe the crystal even
34. CH QUARTZ CRYSTAL MICROBALANCE When the above complex conductance is plotted in polar coordinates one obtains a circle as shown in Figure 20 The vector V indicates the magnitude and phase of the crystal current divided by the applied voltage The real part of the conductance is indicated by the vector R and the imaginary part is indicated by the vector FULL SCALE 200 DOE 3 MARKER 4 987 266 500Hz PHASE REF Odeg MAG UDF gt 115 66E 3 REF POSN O Odeg PHASE CUDF gt D 092deg OSCILLATOR LOCK POINT OSCILLATOR PHASE ERROR OF 15 DEGREES FREQUENCY 4 987966 MHz RESISTANCE 8 60 BANDWIDTH 38Hz 130 000 ZERO PHASE ERROR LOCK POINT TRUE SERIES RESONANCE CENTER 4 987 964 OOOHz SPAN 200 ODOHz AMPTD 10 OdBm Figure 20 Polar Admittance Plot of High Q Crystal 5 12 THEORY OF OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE FULL SCALE 2 SOOOE 3 MARKER 4 986 414 DOOHz PHASE REF Odeg MAG UDF 1 S215E 3 REF POSN O Odeg PHASE UDF 13 518deg FREQUENCY 4 986414 MHz RESISTANCE 6570 Q 1 700 CRYSTAL MEASURED IN GLYCEROL AND WATER SOLUTION FROM AIR TO SOLUTION RESISTANCE CHANGED FROM 8 60 TO 6570 FREQ CHANGED FROM 4 987966 TO 4 987414 MHz Af 526 Hz CIRCLE TOP 4 984964 MHz TRUE SERIES RESONANCE 4 986414 MHz EFFECTIVE PHASE ERROR CIRCLE BOTTOM 4 987914 MHz BANDWIDTH BOTTOM TOP CIRCLE 4 987914 4 984964 MHz 2 950 Hz C
35. CM has one rear panel slot for the optional I O card The card has eight 8 TTL level 0 to 5 volt DC inputs The inputs are pulled up to 5 volts internally through a 4 7 resistor and are set true assuming the input s True level is set to Low by shorting the input pins together There are eight 8 SPST relay outputs capable of handling 120 VA 2A max per relay These inputs and outputs can be used to control external instruments and peripheral devices such as pumps heaters valves instruments etc Figure 32 shows the connector pin configuration and Table 9 1 supplies pin signal assignments Refer to the online help of ROCM computer software for I O definition and programming instructions Figure 32 DB73P I O Rear Panel Connector Table 9 1 DB37P I O Rear Panel Connector Pin Assignments 0 2 1 3 2 4 3 5 4 6 5 7 6 8 7 9 CARD OPTIONAL 9 1 RESEARCH QUARTZ CRYSTAL MICROBALANCE 10 TROUBLESHOOTING GUIDE This section is intended primarily as an aid in understanding the operation and to help insolate possible problems with the RQCM Ifit is determined that the problem lies inside the unit please contact the factory for further assistance Symptom Possible Cause Remedy Line fuse blows when the power switch is switched to on Wrong line voltage is selected at the rear of RQCM Set line voltage on RQCM rear panel to match with line voltage being used Incor
36. Chr 254 Chr 1 Chr 8 Chr 1 Chr 2 Chr 244 If using the IEEE interface then the computer must also send a device clear before the new interface address takes affect The new interface address will take affect immediately when using either RS 232 or RS 485 COMPUTER INTERFACE 7 9 RESEARCH QUARTZ CRYSTAL MICROBALANCE 8 DATA ACQUISITION CARD OPTIONAL The RQCM has one rear panel slot for the optional Data Acquisition Card The card has three 3 temperature inputs to accommodate an RTD thermocouple and thermistor There are also five 5 scalable analog inputs for measuring and logging of DC voltages Except for the thermocouple input which has its own connector all other temperature inputs and analog inputs are on a D SUB 25 pin male connector Figure 30 shows the connector pin configuration and Table 8 1 shows the pin signal assignments Refer to the online help included in the RQCM software for instructions on setting up and programming of these inputs Figure 30 DB25P Data Acquisition Rear Panel Connector Pin Number Function 1 2 3 Voltage Input 1 Input Common Shield 4 5 6 Voltage Input 2 Input Common Shield 7 8 9 Voltage Input 3 Input Common Shield 10 11 12 Voltage Input 4 Input Common Shield 14 15 16 Voltage Input 5 Input Common Shield 17 18 19 Thermocouple Input Hi Lo Shield 20 21 22 23 24 RTD Input Hi Hi Sense Lo Sense Lo Shield 25 Voltage Referen
37. D STATUS Following the receipt of each message the ROCM will send one byte received status message indicating how the message was received with the following format Header Address Inst 253 7 4 COMPUTER INTERFACE RESEARCH QUARTZ CRYSTAL MICROBALANCE Length 2 Instruction Code Receive code Checksum A value of 253 for the instruction byte indicates that this is a received status message The Instruction Code byte indicates the instruction code of the message that was received The following table shows a list of possible receive codes 0 Message received OK Invalid checksum 7 11 INSTRUCTION SUMMARY The following table is a list of valid instruction codes 0 Send configuration Pp Jlmitateautomatic data logging of binary values ooo 2 jSetamalogtodigialboardconfiguraion Inernalcommand Internal command 4 Internal command Set Relay Outputs Internal command Set interface address 7 12 INSTRUCTION DESCRIPTIONS The following is a description of the valid instructions along with an example of how they are used All the examples assume the device address is 1 COMPUTER INTERFACE 7 5 RESEARCH QUARTZ CRYSTAL MICROBALANCE 1 Send hardware configuration Code 0 Instructs the RQCM to send its configuration data to the host computer The following is a description ofthe configuration data message Length bytes
38. ECKOUT Connect the DB9S computer cable to the RS 232 RS 485 port located on the rear of the RQCM Connect the other end of the cable to the computer serial port If you have the GETTING STARTED 2 1 RESEARCH QUARTZ CRYSTAL MICROBALANCE IEEE 488 communication option install the proper cable Refer to Section 7 1 to install setup and run the RQCM software Connect the crystal holder with a crystal installed to the SMB connector labeled Crystal by means of the 24 inch SMB coaxial cable Observe the AC voltage setting on the rear panel Make sure it is set for your local line voltage Plug one end of the power cord to a power outlet and plug the other end into the power entry module in the rear of the RQCM Refer to Figure 4 and Figure 7 for complete system connections If your RQCM is equipped with optional cards refer to their appropriate section for detail instruction on installation and operation Switch the front panel power switch to on All of the red communication LEDS on the front panel will light up for two seconds then some will turn off reflecting the status of the communication lines The green System Ready LED will come on and remain on until the RQCM power is turned off If the System Ready LED fails to turn on then there is an internal problem with the ROCM Please refer to section 10 for troubleshooting Start the RQCM computer program Note that you may have to set the RQCM address and select the correct COM
39. EIR ERG ERR Ee ded 4 10 4 3 1 HOW TO INSTALL CRYSTAL IN A INFICON CRYSTAL 4 10 4 3 2 HOLDER CARE AND ener enhn eene senten nennen 4 12 4 3 3 CONSIDERATIONS FOR BUILDING YOUR OWN HOLDER 4 13 CELL ed 4 13 5 THEORY OF OPERATION nier creep rnb nn en man 5 1 5 1 SAUERBREY EQUATION e a a E a EA A 5 1 92 eerte tm rt ge etm ee roi etae roe E a 5 2 33 IHIEKNESSC ALCULATION 55 rotor e REP 5 3 34 LIQUID MEASUREMENTS ferrei e rr eee emer e a E 5 5 5 4 1 DECAY LENGTH OF SHEAR WAVE IN LIQUID sees 5 8 55 DISSIPATION METHOD iter nter ARE nr eere 5 9 5 6 ELECTRICAL DESCRIPTION OF THE QUARTZ CRYSTAL 5 9 57 CHARACTERIZING THE CRYSTAL een 5 15 5 7 1 FREQUENCY ERRORS tete e eb Seo 5 16 5 7 2 FREQUENCY ERROR DUE TO PHASE nennen eene 5 16 5 7 3 FREQUENCY ERROR DUE TO IMPERFECT CAPACITANCE CANCELLATION 5 17 5 8 FREQUENCY ERRORS DUE TO IMPERFECT CAPACITANCE CANCELLATION 5 18 59 CALCULATING CRYSTAL POWER esee enn enne ran n irea ie 5 19 6 APPLICATIONS iia 6 1 6 1 ELECTROCHEMICAL QUAR
40. ENTER 4 986 314 DOOHz SPAN 20 DOD DOOHz AMPTD 10 OdBm Figure 21 Polar Admittance Plot of Low Q Crystal REF LEVEL DIV MARKER 4 988 314 000Hz 0 0 200 ODOE 6 REAL UDF 1 3851E 3 0 0 200 OOE 6 MARKER 4 988 314 000Hz IMAGINARY IMAG CUDF gt 363 72E 6 SUSCEPTANCE REAL CONDUCTANCE X10 SIEMENS X10 SIEMENS 0 8 0 0 2 80 0 4 60 M 0 CENTER 4 986 314 DOOHz SPAN 20 000 DOOH AMPTD 10 OdBm gt 2 KHz Figure 22 Admittance vs Frequency Real and Imaginary Components of Low Q Crystal The conductance of the L R amp C series arm creates the circle in the polar plot with its center on the real axis The effect of the shunt capacitance conductance is to offset the circle vertically Figure 21 shows a heavily loaded crystal in which the offset is obvious It is the imaginary quadrature current through the shunt capacitance that creates the offset The RQCM provides a THEORY OF OPERATION 5 13 RESEARCH QUARTZ CRYSTAL MICROBALANCE mechanism for canceling out the imaginary current effectively putting the center of the crystal back on the real axis The true series resonant frequency of the crystal 15 then the point where the conductance circle crosses the real axis This is the frequency at which the inductive and capacitive impedance s in the L amp C branch cancel out and the crystal looks like a pure resistance of value R REF LEVEL DIV MARKER 4 986 314 DOOHz 0 0 200 OOE 6
41. F 7__ Discrete Imputs 1 Discrete Outputs 115 The discrete input and output bytes indicate the status of the inputs and outputs such that bit 0 corresponds to input output 1 bit 1 to input output 2 etc All values are sent in Binary format with the most significant byte first To convert binary values to decimal use the following formula Decimal Value Sum of Byte n 256 Y n where n goes from to Y and Y is the total number of bytes that make up the value For example say you want to read sensor frequency You first have to setup the RQCM to send sensor period Say you receive the four following bytes representing sensor period 7 6 COMPUTER INTERFACE RESEARCH QUARTZ CRYSTAL MICROBALANCE 31 255 109 53 This equals 31 256 3 255 256 2 109 256 53 536 833 333 To convert period to frequency use the following formula Frequency Hz 3 221E15 Period 3 221E15 536 833 333 6 000 000 0 Hz Like sensor period sensor resistance is also in special units Use the following formula to convert the resistance counts value sent by the ROCM to OHMs Sensor Resistance OHMs 273 300 Counts 20 The scaling of the analog inputs depends on each inputs configuration as shown in the following table Input Range Scaling mV 0 5 0 0001 5 0 0002 0 10 0 0002 10 0 0005 Example instruct the to output sensor 1 period and resis
42. FLOW CELL 4 13 RESEARCH QUARTZ CRYSTAL MICROBALANCE 5 THEORY OF OPERATION Sauerbrey was the first to recognize the ability of Quartz Crystal Microbalance QCM to measure very small mass changes on the crystal surface His seemingly simple equations have been used for many years and in many different applications 5 1 SAUERBREY EQUATION Equation 1 Af C x Am Where Af Frequency change in Hz Sensitivity factor of the crystal in Hz ng cm 0 0566 Hz ng cm for a 5 MHz crystal 20 C 0 0815 Hz ng cm for a 6 MHz crystal 20 C 0 1834 Hz ng cm for a 9 MHz crystal 20 C Am Change in mass per unit area in g cm The Sauerbrey equations assumed that the additional mass or film deposited on the crystal has the same acousto elastic properties as quartz This assumption resulted in a sensitivity factor Cr which is a fundamental property of the QCM crystal as shown in equation 2 Equation 2 2nx f fv IK mcd Where n Number of the harmonic at which the crystal is driven f Resonant frequency of the fundamental mode of the crystal in Hz Density of quartz 2 648 g cm Effective piezoelectrically stiffened shear modulus of quartz 2 947 10 g cm Solving these equations for Am yields Equation 3 OR E Fi C 2nx f Where fq Resonant frequency of unloaded crystal in Hz f Resonant frequency of loaded crystal in Hz THEORY OF O
43. ICROBALANCE The basic principles and applications of the QCM to electrochemical processes have been extensively reviewed in the electrochemical literature In most electrochemical experiments mass changes occur as material is deposited or removed from the working electrode It is of interest to monitor those changes simultaneously with the electrochemical response and the RQCM is the standard means of doing so As a gravimetric probe the QCM has been used in many types of electrochemical studies including underpotential deposition of metals corrosion oxide formation dissolution studies 383940 adsorption desorption of surfactants and changes in conductive polymer films during redox processes 6 1 1 CALIBRATION Many published literature has demonstrated that when experiments involve only relative frequency shifts which are measured in a fixed solution the offset caused by the viscous loading of the liquid has negligible effect on the accuracy of the Sauerbrey equation for the determination of small mass changes in rigid deposits Quantitative interpretation of the EQCM data in those cases is based on the combination of the Sauerbrey equation and Faraday s law The Sauerbrey equation relates change in frequency to change in mass for thin lossless deposited films whereas Faraday s law relates charge passed in an electrochemical experiment to the number of moles of material electrolyzed Therefore frequ
44. INFICON RQCM Software Version X XX Communication Port 1 I RS232 2 RS 485 3 IEEE488 1 Sensor Board Status Bit0 Ch 1 Bitl Ch 42 Bit2 Ch 3 Accessory Board Status Digital I O Bit Analog Input Total 38 bytes Example To instruct the RQCM to send the configuration data the computer would send Chr 255 Chr 254 Chr 1 Chr 0 Chr 0 Chr 255 2 Automatic Data Logging of Binary Values Code 1 This instruction allows the computer to setup the RQCM to automatically output selected binary values to the communication port every 50 milliseconds The values sent are determined by the bit value of the message byte in the data logging instruction message Byte Bit Description Length Format Range Units bytes 1 0 Message counter 1 Binary Oto255 1 Sensor 1 Period FS 4 Binay Counts sec 2 Sensor 1 Resistance 2 Binary 01065535 Couns 3 Sensor 2Period 4 Binay Counts sec i Counts see 7 _ Analog Input 1 2 Binary 33 3331033 333 Analog Input 2 2 Analog Input 2 33 333 to 33 333 Analog Input 3 Analog Input 4 Analog Input 5 Y 5 lt N 33 333 to 33 333 33 333 to 33 333 Thermocouple Temperature 33 333 to 33 333 0 1 C or F Thermistor Temperature 2 Binary 33 333 to 33 333 0 1 C or F a 4 N 33 333 to 33 333 RTD Temperature 33 333 to 33 333 0 1 C or
45. M port in the Setup Menu in order for the RQCM to communicate with your PC Click on the View Status button to bring up the Status Screen The Status Screen should indicate a crystal frequency within the specified range for the type of crystals being used The frequency should be stable to within a few hertz and the crystal resistance should be between 5 and 15 O for an uncoated polished crystal in air Check the capacitance cancellation by pressing and holding the Reset switch The green Lock LED should light Keeping the Reset switch pressed adjust the fine capacitance trimmer counterclockwise decreasing the capacitance by about 5 degrees The yellow Sweep LED should flash Back the trimmer clockwise to the point where the Sweep LED just stops flashing The capacitance cancellation should be checked and readjusted every time the environment of the crystal and holder is changed if the crystal and holder are moved from air to liquid or liquid to air Remove the crystal The red Unlock LED should light The green Lock LED should go off The Sweep LED should not flash If the Sweep LED flashes the capacitance is under compensated Reinstall the crystal in the holder and repeat the process until it is perfectly compensated Sweep LED not flashing when the crystal is removed Refer to Section 3 4 for more details on adjusting the capacitance cancellation 2 3 1 CRYSTAL MEASUREMENTS VERIFICATION A quick way to test your RQCM is to v
46. MAG UDF 1 5398E 3 D Ddeg 30 000deg MARKER 4 986 314 ODOHz PHASE CUDF 16 983deg MAGNITUDE X10 SIEMENS CENTER 4 986 314 000Hz AMPTD 10 OdBm Figure 23 Admittance vs Frequency Magnitude and Phase of Low Q Crystal 5 14 THEORY OF OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE FULL SCALE 200 OOE 3 MARKER 4 987 965 SOOHz ne PHASE REF Odeg MAG CUDF 115 86E 3 REF POSN O Odeg PHASE UDF gt 0 092deg CRYSTAL BANDWIDTH E T CENTER 4 987 964 OOOHz SPAN 200 DOOHz AMPTD 10 OdBm Figure 24 Non zero Phase Lock Figure 24 shows the result of a non zero phase lock Note that the frequency difference between the top of the conductance circle and the bottom is equal to the bandwidth of the crystal Fora high Q high conductance low resistance crystal the bandwidth is very narrow and small errors in phase lock angle are insignificant For a low Q crystal the bandwidth can be quite large and small phase errors can result in significant frequency errors See the equations in the error discussion section 5 7 CHARACTERIZING THE CRYSTAL MEASUREMENT The INFICON Phase Lock Oscillator used on the Crystal Measurement Card was developed specifically to support the use of the quartz crystal microbalance in the measurement of lossy films and in liquid applications In addition to accurately tracking the frequency of heavily damped crystals the RQCM also tracks the crystal
47. Marc A M High Frequency Impedance Analysis of Quartz Crystal Microbalance 2 Electrochemical Deposition and Redox Switching of Conducting Polymers Anal Chem 66 1994 2926 2934 Ward Michael Investigation of Open Circuit Reactions of Polymer Films Using the QCM Reactionsof Polyvinylferrocene Films J Phys Chem 92 1988 2049 Baker Charles K and Reynolds John R A quartz microbalance study of the electrosynthesis of polypyrrole J Electroanal Chem 251 1988 307 Martin Stephen Granstaff Victoria Edwards and Frye Gregory C Characterization of a Quartz Crystal Microbalance with Simultaneous Mass and Liquid Loading Anal Chem 63 1991 2272 Lucklum Ralf and Hauptmann Peter The Df DR QCM technique an approach to an advanced sensor signal interpretation Electrochimica Acta 45 2000 3907 5 Etchenique and Calvo E L Gravimetric measurement in redox polymer electrodes with the EQCM beyond the Sauerbrey limit Electrochemistry Communications 1 5 1999 167 Etchenique R A and Calvo J Electrochemical Quartz Crystal Impedance Study of Redox Hydrogen Mediators for Amperometric Enzyme Electrodes Anal Chem 69 1997 4833 57 Johannsmann Diethelm Viscoelastic Analysis of Organic Thin Films on quartz resonators Macromol Chem Phys 200 1999 501 Reed E Kanazawa Keiji and Kaufman J Physical description of a viscoelastically loaded AT c
48. N d33MS 15 35 JINVLIOVAVIO L I3NNVHO Figure 2 Crystal Channel Description 3 4 OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE 3 4 ADJUSTING THE CAPACITANCE CANCELLATION Proper adjustment of the Capacitance Cancellation is critical in obtaining accurate results with high resistance heavily damped crystals See Section 5 8 The cancellation adjustment should be performed with the crystal holder and crystal in the measurement environment For instance if liquid measurements are to be made insert the crystal and its holder into the liquid where the measurement will be made With the crystal and holder in the measurement environment press and hold the Reset switch Pressing and holding the Reset switch forces the VCO to its minimum frequency turns on the Lock LED and turns off the quadrature current injector Forcing the VCO to its minimum frequency insures that the crystal is being driven at a frequency far from its resonant frequency where its impedance 5 essentially due only to the shunt electrode capacitance With the quadrature current injector turned off the measured current is due only to the net shunt capacitance The measured net shunt capacitance is the capacitance of the cable holder and crystal electrodes minus the compensation capacitance If the capacitance is under compensated the phase of the measured current leads the voltage a phase angle of plus 90 degrees
49. OPERATION AND SERVICE MANUAL ROCM Research Quartz Crystal Microbalance IPN 603800 Rev J 6 INFICON OPERATION AND SERVICE MANUAL ROCM Research Quartz Crystal Microbalance IPN 603800 Rev J 4 INI ICON Instruments for Intelligent Control www inficon com reachus inficon com Due to our continuing program of product improvements specifications are subject to change without notice 2007 INFICON Trademarks The trademarks of the products mentioned in this manual are held by the companies that produce them INFICON is a trademark of INFICON Inc All other brand and product names are trademarks or registered trademarks of their respective companies Disclaimer The information contained in this manual is believed to be accurate and reliable However INFICON assumes no responsibility for its use and shall not be liable for any special incidental or consequential damages related to the use of this product Disclosure The disclosure of this information is to assist owners of INFICON equipment to properly operate and maintain their equipment and does not constitute the release of rights thereof Reproduction of this information and equipment described herein is prohibited without prior written consent from INFICON Two Technology Place East Syracuse NY 13057 9714 Phone 315 434 1100 See www inficon com Copyright 2002 All rights reserved Reproduction or adaptation of any par
50. PERATION 5 1 RESEARCH QUARTZ CRYSTAL MICROBALANCE It is important to note that under these assumptions the change in frequency is a function of mass per unit area Therefore in theory the QCM mass sensor does not require calibration However keep in mind that the Sauerbrey equation is only strictly applicable to uniform rigid thin film deposits Vacuum and gas phase thin film depositions which fail to fulfill any of these conditions actually exhibit more complicated frequency mass correlations and often require some calibration to yield accurate results 5 2 Z MATCH EQUATION Sauerbrey s original assumptions were of course questionable and indeed work with crystals heavily loaded with certain materials showed significant and predictable deviations between the measured mass and that predicted by Equation 3 Lu and Lewis analyzed the loaded crystal as a one dimensional composite resonator of quartz and the deposited film which led to the equation shown below which is also referred to as the Z Match equation Am E a R f f Am change in mass per unit area in g cm Equation 4 where 2 Frequency Constant for AT cut quartz crystal 1 668 x 10 Hz x cm Density of quartz 2 648 g cm Resonant frequency of unloaded crystal in Hz f Resonant frequency of loaded crystal in Hz Z Factor of film material falig Acoustic Impeda
51. QCM to create a graph of mass and current versus potential Control of external instruments and peripheral devices is accomplished with an optional input output card Each remote I O card provides eight remote inputs and eight relay outputs The functions of the inputs and outputs are defined in the RQCM s software with some typical uses including the control of pumps heaters valves instrument initiation etc 1 4 FEATURES 1 1 1 VERY WIDE FREQUENCY RANGE The RQCM supports a wide frequency range from 3 8 to over 6 MHz It will support both 5 and 6 MHz crystals and with a low limit of 3 8 MHz it will support 1 2 MHz of frequency shift on a 5MHz crystal A frequency range of 5 1 to over 10 MHz is also available 1 1 2 SUPPORT FOR VERY LOW HIGHLY DAMPED CRYSTALS The RQCM will accurately measure crystals with resistances up to 5 KO In most cases it will maintain lock up to a resistance of 10 KO or more It will support crystal oscillation in highly viscous solutions of more than 8896 glycol in water 1 1 3 DIRECT REAL TIME MEASUREMENTS OF CRYSTAL FREQUENCY MASS AND RESISTANCE The RQCM accurately measures crystal frequency mass and resistance The software uses this data to derive various physical parameters of the deposited film or media at the surface of the crystal GENERAL DESCRIPTION 1 1 RESEARCH QUARTZ CRYSTAL MICROBALANCE 1 1 4 MULTIPLE CRYSTAL MEASUREMENT CHANNELS The RQCM can be configured to measur
52. RATURE OF INFICON 1 AT CUT CRYSTAL FOR 90 4 6 RE 11 FREQUENCY VS TEMPERATURE OF INFICON 1 AT CUT CRYSTAL FOR 25 4 7 RE 12 CHC 100 CRYSTAL HOLDER uneni nienn eere 4 10 RE 3 CRYSTAL INSTALLATION 20 ne er eee eee A dee I 4 11 RE 14 FREQUENCY CHANGE VS WT 5 7 RE 15 RESISTANCE CHANGE VS WT GLYCEROL 222 2 0 10 0010000000000000000000000000 5 8 RE 16 CRYSTAL EQUIVALENT CIRCUIT ee tee tette o oer title e RT 5 9 RE 17 POLAR PLOT OF CRYSTAL ADMITTANCE 02020000000000010000000000000000 5 10 RE 18 ADMITTANCE VS FREQUENCY MAGNITUDE AND PHASE OF HIGH Q CRYSTAL 5 11 RE 19 ADMITTANCE VS FREQUENCY REAL AND IMAGINARY COMPONENTS OF HIGH Q CRYSTAL 5 11 RE 20 POLAR ADMITTANCE PLOT OF HIGH CRYSTAL 2 11222 2 244000000000 000000000000 5 12 RE 21 POLAR ADMITTANCE PLOT OF LOW Q CRYSTAL 2 4 142000 0000400000000000000000000000000000 81 5 13 RE 22 ADMITTANCE VS FREQUENCY REAL AND IMAGINARY COMPONENTS OF LOW Q CRYSTAL 5 13 RE 23 ADMITTANCE VS FREQUENCY MAGNITUDE AND PHASE OF LOW CRYSTAL 5 14 RE24NON ZERO PHASE LOK nice main ideada esie 5 15 RE 25 EQUIVALENT PHASE ERROR DUE TO IMPERFECT CAPACITANCE CANCELLATION
53. TZ CRYSTAL MICROBALANCE 6 1 6 1 1 CALIBRATION ei ii testem WR Y HR ER ER e didas 6 1 6 1 2 POLYMER MODIFIED ELECTRODES inorren niaminini a i ea 6 2 6 2 CHEMICAL AND BIOLOGICAL 5 5 6 2 7 COMPUTERINTERFAGE 00000000 7 1 7 1 COMPUTER INTERFACE E E 7 1 72 RECOMMENDED MINIMUM COMPUTER CONFIGURATION 7 1 7 3 SOFIWAREINSTALLXTION rettet 7 1 7 4 CREATING YOUR OWN SOFTWARE eene en een ener 7 1 ORS 232 SERIA L INTERFACE m eerte Re rares 7 1 7 6 RS 48S SERIALINTERFACE dci 7 2 17 IEBE 488 PARALLEL INTERFACE 7 3 1 8 PROTOCOL enean A mte eem eem 7 4 95 CDATA TYPES EA ome eem ee ime mes 7 4 740 MESSAGE RECEIVED STATUS erret di 7 4 TALL INSIRUCTION SUMMARY tt 7 5 712 INSTRUCTION 5 a 7 5 8 DATA ACQUISITION CARD 8 1 8 1 VOLFAGEINPUTS tee err ete rrt e oen t er 8 1 8 2 TEMPERATURE INBUTS rhet ttt three eem te trie ete sees 8 2 8 2 1 THERMISTOR INPUT treni ttt rre 8 2 6 2 2 RIDIN OL secs ot edere t eH ee UE P cnet eget 8 2 8 2 3 THERMOCOUPBLE INPUT te iiti epit eie
54. TZ CRYSTAL MICROBALANCE Voc Open Circuit crystal drive voltage 125 mV R Crystal drive source resistance 20 ohms Crystal resistance value ohms Examples 1 250 200 o Crystal Power uW Figure Crystal Resistance 80 ohms Pory in watts 0 125 20 80 80 1 25E watts or 125 pW Crystal Resistance 4000 Q Pary in watts 0 125 20 4000 4000 3 87E watts or 3 87 pW Crystal Power vs Crystal Resistance o e D e e eo N 9 e e N 10000 456 224 144 103 Crystal Resistance ohms 27 Crystal Power Dissipation vs Crystal Resistance 5 20 THEORY OF OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE 6 APPLICATIONS The RQCM will respond very sensitively to minute stress changes on its vibrating surface resulting from mass deposits or frictional forces This makes 1t a powerful tool for a wide variety of applications including biofilms formations on surfaces bio sensing specific gas detection environmental monitoring and basic surface molecule interaction studies A full spectrum of its potential applications is beyond the scope of this manual This section only describes a few typical applications The user is advised to consult the publications listed in Section 12 for further information 6 1 ELECTROCHEMICAL QUARTZ CRYSTAL M
55. The RQCM is designed for many types of research applications where Quartz Crystal Microbalance measurement is desired Included with each instrument is a Windows based software package that allows the user to configure the RQCM setup multiple experiments log data with real time graphing and review results from previous experiments The QCM portion of this system accurately measures crystal frequency and crystal resistance for up to three crystals simultaneously The software uses this data to derive various physical parameters of the deposited film and or the liquid or gas environment at the surface of the crystal The heart of the system 1s a high performance phase lock oscillator PLO circuit that provides superior measurement stability over a wide frequency range 3 8 to 6 06 MHz or 5 1 to 10 MHz The circuit incorporates adjustable crystal capacitance cancellation reducing error caused by the parasitic capacitance of the crystal cable and fixture Capacitance cancellation is essential for accurate measurements of lossy soft films Data collection from external sources is accomplished with an optional Data Acquisition Card which provides three temperature inputs RTD Thermocouple and Thermistor as well as five scalable analog inputs For example you can use the analog inputs to acquire potential and current data from a potentiostat during a cyclic voltammogram The RQCM allows you to combine this data with the mass data of the
56. als Refers to the crystal s frequency response range bounced by the frequency values cross at half the resonance frequency s magnitude It is defined as f Q resonance frequency crystal Q A device that houses the crystal and provides connections to the crystal s electrodes via a coaxial connector A figure of merit used in describing the sharpness of the crystal response It is also called crystal quality factor Pennwalt s registered trademark of Polyvinilidene Fluoride PVDF a homopolymer of 1 1 di fluoro ethene is a tough thermoplastic that offers unique properties including high chemical inertness low permeability to gases and liquids resistance to radiation and excellent mechanical strength and toughness Visit www atofinachemicals com for more detailed information 1077 farads A common unit of capacitance abbreviated as pfd By definition 1 farad will store a 1 Coulomb charge when connected across a 1 volt potential Phase Lock Oscillator A type of electronic circuit in which the frequency and the phase of the Voltage Controlled Oscillator VCO is locked to the frequency and the phase of a reference signal in our case the signal from the sensing crystal Refers to the imaginary component of the current through the shunt capacitance Cs INFICON QCM instrument s model name which stands for Research Quartz Crystal Microbalance Resistance Temperature Detector device that changes its resistance as a func
57. ant processes Sensitive selective detection of biochemically active compounds can be achieved by employing antigen antibody enzyme substrates and other receptor protein pairs The potential analytical applications of these materials has been reviewed particularly with respect to the development of biochemical sensors QCM studies have provided detailed information about the functionalized surfaces developed for a range of biochip and biosensor applications INFICON RQCM is now being applied routinely by biologists and biochemists to obtain information about processes such as protein adsorption desorption cell adhesion protein protein interaction degradation of polymers biofouling and biofilm formation drug analysis and DNA biosensors APPLICATIONS 6 3 RESEARCH QUARTZ CRYSTAL MICROBALANCE 7 COMPUTER INTERFACE Three different interfaces are available to connect the hardware to your computer The RQCM system comes standard with an RS 232 serial interface Both RS 485 and IEEE 488 interfaces are available as options Currently the does not offer a Universal Serial Bus USB interface However you can use an inexpensive RS 232 to USB adaptor if your computer does not have RS 232 port available Refer to the Data Logging on line help for more details 7 1 COMPUTER INTERFACE SOFTWARE Your RQCM software is supplied on CD Extensive on line help makes a hardcopy manual unnecessary
58. ase to flash Back off one stop so the flashing begins again The course adjustment is complete Slowly adjust the fine trimmer clockwise increasing capacitance until the flashing of the Sweep LED just stops The capacitance compensation adjustment is now complete Release the Reset button and assuming the crystal is not dead or out of range the will lock on it 3 5 1 AS A GENERAL RULE The Reset switch must be depressed during the adjustment for capacitance cancellation Capacitance cancellation is essential for accurate measurements of liquids and lossy soft 3 6 OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE films Use shortest cable possible for connection from the Crystal Holder to Cables capacitance changes with temperature and position the longer the cable the larger the capacitance hence the larger change in capacitance Capacitance cancellation should be checked and readjusted every time the environment of the crystal is changed for example transition from air to a liquid phase The capacitance cancellation adjustment must be performed with the Crystal Holder and crystal in the actual measurement environment 3 6 WORKING WITH VERY LOW Q CRYSTALS Very low Q crystals require very close adjustment of the compensating capacitance to insure a successful lock To adjust the compensation capacitance one pushes the Reset button and adjusts the capacitance to the point where
59. c thin films in EQCM systems is complex because the shear wave exists simultaneously in the quartz crystal the viscoelastic film and the adjacent solution so reflection of the shear wave must be taken into account However solution of this problem would be worthwhile especially if the material properties of the film could be derived This would allow correlation of the electrochemical behavior of the film with its material properties The unique property of the QCM technique is its ability to determine the mass of very thin layers while simultaneously giving information about their viscoelastic properties The ability to measure both mass and structural changes means it is possible to detect phase transitions cross linking and swelling in polymeric thin films 6 2 CHEMICAL AND BIOLOGICAL SENSORS A QCM will response to anything that has mass Thus it is imperative for the QCM user to develop a condition where the QCM will only response to the analyte of interest i e build a unique sensitivity into the sensor crystal This usually involves a chemically or biologically sensitive layer applied to the surface of the crystal In recent years QCM applications have seen a dramatic increase in field of biochemical analysis QCM devices are routinely used as biochemical and immunological probes as well as for the 6 2 APPLICATIONS RESEARCH QUARTZ CRYSTAL MICROBALANCE investigation and or monitoring of biochemcially signific
60. ce 13 Not used Table 8 1 DB25P Data Acquision Rear Panel Connector Pin Assignments 8 1 VOLTAGE INPUTS Each of the five analog inputs can be configured as 0 to 5V 0 to 10V 5V or 10V The unipolar positive inputs can be connected as unipolar negative inputs The resolution of the data is dependent on the range selection as shown in the table below Configuration Resolution 0 to 5V 0 1 mV 0 to 10V 0 2 mV 5V 0 2 mV 10V 0 5 mV Table 8 2 Input Voltage Resolution The voltage input pairs are labeled as Input and Common The Input pin is the positive input and the Common pin is the negative input The common mode range is 200V so the Common pin can be used to read unipolar negative voltages with the input pin as common Each input also has a Shield pin for shielded cable termination Shielded twisted pair cable is recommended for connections longer than a foot DATA ACQUISITION CARD OPTIONAL 8 1 RESEARCH QUARTZ CRYSTAL MICROBALANCE 8 2 TEMPERATURE INPUTS Three temperature inputs are included to support the three most commonly used temperature sensors thermistor Resistance Temperature Detector RTD and type T copper constantan thermocouple 8 2 1 THERMISTOR INPUT The Thermistor Input is designed to use an Omega 10 25 C Precision Interchangeable Thermistor P N 44006 or equivalent Shielded twisted pair is recommended for the leads Thi
61. ctance in H D can be determined from R if L is known It has been shown that L will remain constant unless there is an acoustic resonance in the film on the crystal Independent studies have shown that as long as the effect of the parasitic capacitance Cs is properly cancelled the results provided by the RQCM System are in good agreement with those obtained by the Dissipation Method 5 6 ELECTRICAL DESCRIPTION OF THE QUARTZ CRYSTAL Figure 16 shows the equivalent circuit of a quartz crystal The circuit has two branches The motional branch which contains the L R amp C is the branch that is modified by mass and viscous loading of the crystal The shunt branch which contains the lone Cs element represents the shunt capacitance of the crystal electrodes and any cable and fixture capacitance Figure 16 Crystal Equivalent Circuit THEORY OF OPERATION 5 9 RESEARCH QUARTZ CRYSTAL MICROBALANCE Because a crystal s impedance is minimum at resonance it is convenient to characterize a crystal in terms of admittance Admittance is the inverse of impedance Y 1 Z thus the admittance reaches a maximum at resonance While impedance is proportional to the voltage developed across a device when it is subjected to a current the admittance is proportional to the current through the device when it is subjected to a voltage At any frequency the admittance of a quartz crystal is a complex value that can be expressed in t
62. ctrodes J Electrochem Soc 138 33239 137 139 at Benje Michael Eierman Matthias Pittermann Udo Weil Konrad G An Improved Quartz Crystal Microbalance Applications to the Electrocrystallization and dissolution of Nickel Ber Bunsen Ges Phys Chem 90 1986 435 439 38 Tudos Anna J Johnson Dennis Dissolution of Gold Electrodes in Alkanine Media Containing Cysteine Anal Chem 67 1995 557 560 32 Schumacher R Muller A Stockel W An In Situ Study on the Mechanism of the Electrochemical Dissolution of Copper in Oxygenated Sulphuric Acid An Application of the Quartz Microbalance J Electroanal Chem Interfacial Electrochem 219 1987 311 317 40 Ostrom Gregory S Buttry Daniel A Quartz crystal microbalance studies of deposition and dissolution mechanisms of electrochromic films of diheptylviologen bromide J Electroanal Chem Interfacial Electrochem 256 1988 411 431 Auge Jorg Hauptmann Peter Eichelbaum Frank and Rosler Stephen sensor in liquids Sensors and Actuators 18 19 1994 518 Mo Yibo Hwang Euijin Scherson Daniel A Simultaneous Normalized Optical Reflectivity and Microgravimetric Measurements at Electrode Electrolyte Interfaces The Adsorption of Bromide on Gold in Aqueous Media 67 1995 2415 2418 Schneider Thomas W Buttry Daniel A Electrochemical Quartz Crystal Microbalance Studies of Adsorption and Desorpt
63. d onto the crystal This resistance value can be used to determine when a crystal reaches a maximum loading 4 4 9 TEMPERATURE COEFFICIENT The temperature coefficient of quartz crystals is normally specified in units of parts per million per degree of temperature change A one part per million change in frequency of the sensing crystal corresponds to an indicated thickness change of approximately 7 4 for a material with a density of 1 0 gm cm For Aluminum with a density of 2 7 gm cm this is equivalent to approximately 2 7 This intrinsic dependence of resonance frequency of a sensor crystal on temperature is generally small in experiments in gas phase when operating at or near its turn around point The turn around point is where the temperature coefficient of the crystal is zero That is there is no change in resonance frequency due to a change in the temperature of the crystal at the turnaround point INFICON 1 inch crystals are optimized for two operating temperatures namely 90 C and 25 C These crystals have very good temperature stability when operating close to their specified temperature Even though AT cut crystals are designed to minimize the change in frequency due to temperature the effect of temperature can be significant when attempting to resolve small mass frequency changes over long periods of time This frequency change due to temperature is magnified when the sensor crystal is submerged in liquids This 1s d
64. e 3 9 OPERATION GUIDELINES This section offers some general guidelines to help minimize errors in the measurements due to the environment of the sensor crystal It is the user s discretion as which are best to utilize for a particular experiment Keep the following tips in mind when setting up an experiment 3 9 1 ALLOW THE RQCM TO WARM UP Allow for about one to two hours of warm up time for the RQCM s electronics to reach temperature equilibrium 3 9 2 ISOLATE THE RQCM FROM TEMPERATURE CHANGE Limit temperature changes of the RQCM s environment as this will cause small changes in the measured crystal frequency The most likely source that alters the RQCM temperature is the room air conditioning system Keep the away from the direct path of air conditioning vents 3 9 3 FOR OPERATION IN AIR In gas phase measurements the single factor that is most likely to induce frequency instability or OPERATION 3 9 RESEARCH QUARTZ CRYSTAL MICROBALANCE drift is temperature Review section 4 1 9 for more information on the crystal s response to temperature 3 9 3 1 Operate at or Near The Crystal s Turn Around Point When possible perform the experiment at the sensor crystal s turn around point At or near this temperature most of the errors due to temperature are negligible The turn around point is where the temperature coefficient of the crystal is zero That is there is no change in res
65. e sample being cleaned A flow of air or a weak vacuum carries off the organics This method does not affect the quartz surface it is low cost and is very efficient Oxygen plasma cleaning is another effective method that will remove organic matters In this method the plasma reaction breaks up organic matters at the surface of the sample being cleaned into smaller molecules and a vacuum pump removes them from the surface of the sample 4 2 1 3 Biomaterials lipids proteins and similar biomolecules Start by treating the crystal in an UV ozone chamber for 10 minutes then immerse it into a 1 1 5 solution of hydrogen peroxide 3096 ammonia 2590 and deionized water heated to a temperature of about 75 C for 5 minutes 22 Immediately rinse liberally with deionized water and dry in a gentle flow of nitrogen gas Immediately before measurement treat the crystal with UV ozone for 10 minutes 4 2 1 4 Lipid vesicles on SiO surfaces Treat the crystal in an UV ozone chamber for 10 minutes then immerse it into water with 2 of sodium dodecyl sulfate SDS at room temperature for 30 minutes 23 Rinse generously with deionized water and blow dry with filtered nitrogen gas Immediately before measurement treat the crystal with UV ozone for 10 minutes 4 2 1 5 Polystyrene removal To clean polystyrene PS off a crystal immerse the crystal into a 1 1 solution of hexane and deionized water and treat it in an ultrasonic bath for 1 minute Rinse thor
66. e up to three crystal measurement channels simultaneously 1 1 5 ELECTRODE CAPACITANCE CANCELLATION The total quartz crystal impedance includes a shunt capacitance due to the capacitance of the crystal electrodes cable and holder in parallel with the series resonant arm The total current through the crystal is the sum of the current through the shunt capacitance plus the current through the series resonant arm The physical motion of the crystal is reflected in the values of the L R and C in the series arm of the crystal only and therefore we want to subtract out or otherwise cancel the current through the shunt electrode capacitance The Crystal Measurement Card includes a method of canceling the electrode capacitance insuring that the measured crystal current does not include the current through the electrode capacitance and therefore is essentially the current through the series resonant arm of the crystal only 1 1 6 AUTOLOCK When the PLO loses lock the VCO Voltage Controlled Oscillator is ramped up to the maximum frequency at which time it is automatically reset to the minimum frequency and a new scan is initiated To insure that the VCO ramps up in frequency a small amount of quadrature current is injected into the current to voltage buffer whenever the PLO is unlocked This current is equivalent to a shunt capacitance of about 1 5 pfd As soon as lock is detected the quadrature current is turned off 1 1 7 CRYSTAL FACE ISOL
67. ed and constitutes fulfillment of all of INFICON s liabilities to the purchaser INFICON does not warrant that the product can be used for any particular purpose other than that covered by the applicable specifications INFICON assumes no liability in any event for consequential damages for anticipated or lost profits incidental damage of loss of time or other losses incurred by the purchaser or third party in connection with products covered by this warranty or otherwise 6 INFICON www inficon com reachusQinficon com TABLE OF CONTENTS 1 GENERAL DESCRIPTION dan 1 1 1 1 FEATURES eite HERE ne a 1 1 1 1 1 VERY WIDE FREQUENCY 1 1 1 1 2 SUPPORT FOR VERY LOW O HIGHLY DAMPED 1 1 1 1 3 DIRECT REAL TIME MEASUREMENTS OF CRYSTAL FREQUENCY MASS AND RESISTANCE tinc LO dL A Er att UE M 1 1 1 1 4 MULTIPLE CRYSTAL MEASUREMENT 5 1 2 1 1 5 ELECTRODE CAPACITANCE CANCELLATION esses 1 2 1 1 6 SAUTOLOCK 1 2 1 1 7 CRYSTAL FACE ISOLATION sess eee ener ennt enne ener tenere ener 1 2 1 1 8 FULLY INTERGATED COMPUTER 1 2 1 1 9 INPUTS AND OUTPUTS 000000000000 1 2 1110 1 2
68. ency changes can be related to the total charge passed An example would be the electrodeposition of Ag on a Pt electrode QCM crystal The charge Q is an integral measure of the total number of electrons delivered at the interface during the reduction process To the extent that each electron supplied results in the deposition of one atom of Ag there should be a linear relationship between Q and Af as is given by this next equation Equation 11 10 My n F A where Af frequency change in Hz apparent molar mass of the depositing species grams mole C Sauerbrey s sensitivity factor for the crystal used APPLICATIONS 6 1 RESEARCH QUARTZ CRYSTAL MICROBALANCE O integrated charge during the reduction in Coulombs number of electrons transferred to induce deposition n 1 for Ag deposition A active deposition area of the working liquid contact electrode in cm Faraday s constant 9 648 10 Coulomb mole A plot of Af vs will deliver the apparent mass per electron of the deposited species when n is taken into account This is often used to elucidate the mass changes that accompany redox processes and hence is very useful for characterizing the mechanisms of electron transfer reactions However before any calculations can be performed based on Equation 11 the EQCM must be calibrated in order to properly derive 1 the proportionality constant Cs of the Sau
69. ent circuit model Figure 16 was applied to derive a linear relationship between the change in series resonance resistance AR of the crystal and 7 under liquid loading Using the relations in this study the change in resistance AR can be put in the form Equation 8 2 lp u V AR 5 5 f 32 A o ex Where AR change in series resonance resistance in Q active area of INFICON 1 inch crystal 3 419 107 m piezoelectric constant for an AT cut quartz 0 095 kg sec V For example moving the crystal from air to pure water 20 C Equation 7 and Equation 8 predict a decrease in of 714 Hz and an increase in R of 357 4 respectively These values are in agreement with the results observed with an RQCM using a 5 MHz 1 inch diameter polished gold coated mounted on a INFICON Crystal Holder Note that pure water a 20 C has a density of 998 2 kg m and a viscosity of 1 002x 107 N sec m Excellent agreement between the frequency and resistance equations and the experimental results has been proved 2526 making the QCM an excellent tool for the evaluation of fluid properties Application examples include in situ monitoring of lubricant and petroleum properties The tight correspondence between theory Equation 7 and Equation 8 and the ROCM is clearly 5 6 THEORY OF OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE illustrated by Figure 14 and Figure 15
70. erbrey equation in solution and 2 to account for the effective area of the working electrode This is generally done using a well behaved electrochemical reaction typically electrodeposition of silver copper or lead on a gold or platinum electrode Several calibration procedures are described in the electrochemistry literature 47 6 1 2 POLYMER MODIFIED ELECTRODES The EQCM has been extensively used to study polymer modified electrodes particularly as a gravimetric tool to follow redox processes However for the linear frequency to mass relationship described by Equation 11 to hold true the polymer over layer must exhibit no changes in rigidity during the electrochemical process Otherwise the viscoelastic changes will also contribute to the frequency change leading to an erroneous interpretation of the mass changes 52 As a consequence it is important to determine if viscoelastic properties of the polymer film influence the frequency measurement during polymer film experiments A straightforward method to detect changes in film viscoelastic properties of redox films is to simultaneously monitor the series resonance resistance R of the quartz oscillator during the electrochemical experiment 7 Some theoretical models based on the simultaneous measurement of Af and AR have been discussed in the literature for the extension of EQCM gravimetric measurements to lossy films The viscoelastic analysis of polymeri
71. erial Density and Acoustic Impedance Value gm cm 2 10 5gm cm 2sec Barium 735 420 Beryllium 185 1626 Bismuth Bi fos Jui Boron B 124 270 Copper 1 Sulfide alpha Copper 1 Sulfide beta Europium 1524 J Lead 1130 1781 Lithium i Lithium Fluoride i Magnesium Magnesium Fluoride Magnesium Oxide Manganese Manganese Sulfide Mercury Molybdenum Nickel Niobium i b 9 5 oa ra ua ri 5 4 THEORY OF OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE Palladium mo 24 73 Platinum 10 22 12 40 10 15 8 25 16 69 7 48 1 84 5 62 Strontium Sulphur 3 86 Tantalum 33 70 Tantalum Oxide 29 43 Tellurium 9 81 Terbium Tb 0 8272 13 38 Thallium 1185 570 12 20 14 06 22 07 54 17 58 48 Uranium 37 10 Vanadium 16 66 Uranium Vanadium 7 81 10 57 17 18 15 88 12 23 11 39 5 4 LIQUID MEASUREMENTS QCMs have been used as gas phase mass detectors with lossless films for many years However only recently has their applications been extended to liquids and with viscoelastic deposits In these cases both frequency and series resonance resistance of the quartz crystal are important to completely characterize the material and or the liquid in contact with the crystal electrode The development of QCM systems for use in liquids opened a new world of applications including electrochem
72. erify its measurements of frequency and resistance in air and in water The measurement values of frequency and resistance are as follows For a thorough test the crystal can be immersed in a series of viscous glycerol water solutions at 20 C and compare its measurement values against the predicted results shown in Figure 14 and Figure 15 2 3 1 4 In Air If you are using INFICON 1 Polished 5 MHz Gold Electrode Crystal after compensated for the capacitance the frequency should be between 4 976 to 5 020 MHz and the resistance should be between 5 to 15 ohms Record the frequency and resistance values 2 2 GETTING STARTED RESEARCH QUARTZ CRYSTAL MICROBALANCE 2 3 1 2 In Water Submerge the crystal holder into room temperature water 20 C and adjust for capacitance The frequency should decrease 721 Hz and the resistance should increase 364 ohms from the values recorded in air GETTING STARTED 2 3 RESEARCH QUARTZ CRYSTAL MICROBALANCE 3 OPERATION The heart of the RQCM is the crystal measurement methodology It is important that the user understand its operation to ensure proper setup and application 3 1 GENERAL DESCRIPTION OF THE CRYSTAL MEASUREMENT The INFICON Phase Lock Oscillator used on the Crystal Measurement Card was developed specifically to support the use of the quartz crystal microbalance in the measurement of lossy films and in liquid applications In addition to accurately tracking the fre
73. erms of magnitude and phase or in terms of a real and imaginary value The relationship of these two representations is shown in Figure 17 IMAGINARY COMPONENT OR QUADRATURE REAL COMPONENT Figure 17 Polar Plot of Crystal Admittance Figure 18 shows the conductance in terms of magnitude and phase while Figure 19 shows the same information in terms of the imaginary and real part of the conductance 5 10 THEORY OF OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE REF LEVEL DIV MARKER 4 987 964 DODHz D O 20 DODE 3 MAG UDF 115 64E 3 D Odeg 30 000deg MARKER 4 987 964 OOOHz PHASE UDF 3 877deg PHASE BANDWIDTH MAGNITUDE DEG apis ss X10 SIEMENS 45 3 120 0 100 3 45 60 CENTER 4 987 964 DODHz SPAN 200 OODHz AMPTD 10 OdBm Figure 18 Admittance vs Frequency Magnitude and Phase of High Q Crystal REF LEVEL DIV MARKER 4 987 964 DOOHz 0 0 20 000 REAL UDF 114 94E 3 0 0 20 000E 3 MARKER 4 987 964 OOOHz IMAC UDF 5 8850 wew Tl SUSCEPTANCE PEA CONDUCTANCE X10 SIEMENS IMAGINE BANDWIDTH EE X10 SIEMENS RREN EI puse S ASAS Bl CENTER 4 987 964 OOOHz SPAN 200 OOOHz AMPTD 10 OdBm 80 60 40 Figure 19 Admittance vs Frequency Real and Imaginary Components of High Q Crystal THEORY OF OPERATION 5 11 RESEAR
74. fect the sensor signal 3 9 4 1 Degas The Sample Liquid The sample liquid should be degassed prior to measurement to avoid the formation of air bubbles on the surface of the crystal 3 9 4 2 Wait For Mechanical Disturbances To Stabilize To minimize random fluctuations cause by vibrations it is best to immerse the holder with a crystal installed in the sample solution several hours before the experiment is started 3 9 4 3 Wait For The Temperature To Stabilize To avoid the formation of air bubbles and reduce temperature related artifacts the sample liquid should have approximately the same temperature as the measurement chamber s working temperature 29 Wait at least one hour after a holder is immersed in a liquid to allow for the crystal to come to equilibrium before performing any accurate measurements 3 10 OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE 3 9 4 4 Prepare Your Solutions Carefully To avoid effects due to changes in the properties of the buffer liquid or solvent solutions should be prepared carefully Whenever possible use purified samples at high concentration and dilute them in the appropriate buffer or solvent just before measurement Use solvents or buffers from the same stock during one measurement 3 9 4 5 Avoid Using A Stirrer If possible avoid using a magnetic stirrer Stirrers create turbulences However many solutions often require the use of a magnetic stirrer to keep a solution
75. he Sauerbrey equation is only strictly applicable to uniform thin film deposits originating from a low pressure 1 e vacuum gas environment Thick deposits and operation in liquid environments or in contact with lossy films relies on the use of more complex equations relating the frequency shifts to mass loading and often requires calibration of the setup for accurate results Several articles have been published on simple ways to calibrate the mass sensitivity of QCMs for electrochemical applications and for vacuum thin film deposition processes 7 and some useful calibration guidelines are also described herein Many studies have shown that the crystal s sensitivity is approximately Gaussian The maximum sensitivity is in the center of the crystal and it tapers off towards the edge of the active area 19 The mass sensitivity distribution has also been shown to become slightly more confined to the electrode region as the mass loading is increased 4 4 7 STABILITY A sensor crystal cannot distinguish the difference between a frequency shift due to deposited material or that due to other disturbances Thus any extraneous factors other than the deposited mass which may cause the quartz crystal to change its resonant frequency must be properly controlled Factors that can influence the stability of a sensor crystal are categorized as follows The crystal itself Improper design localized stress damage to the crystal The cr
76. ing carbon such as carbon dioxide are usually not considered to be organic but rather are classed as inorganic Ultra Violet Ozone The UVO cleaning method is a photo sensitized oxidation process in which the contaminant molecules are excited and or dissociated by the absorption of short wavelength UV radiation Near atomically clean surfaces can be achieved using this method The basic instrumentation required this process includes a UVO chamber a gas oxygen supply or an exhaust system For more information visit http www jelight com uvo ozone cleaning htm This method utilizes high frequency ultrasonic and high intensity sound waves into a liquid producing cavitations rapid formation and collapse of minute cavities in a cleaning liquid For more information visit http www aqueoustech com images UltrasonicPrimer PDF RESEARCH QUARTZ CRYSTAL MICROBALANCE Plasma Cleaning A method that utilizes plasma reaction at the surface of the sample and volatile by products are removed by the vacuum pump The basic instrumentation required this process includes a reaction chamber a power supply and a vacuum source The sample being cleaned is put into the chamber which is evacuated by the vacuum pump Gas oxygen is introduced into the chamber and converted to reactive plasma by the power supply For more information visit http www marchplasma com Silanization The chemical conversion of hydroxyl OH groups which often
77. ion near zero phase the frequency error per degree of phase error is given by the following formula Frequency Error 2 Phase Error in radians Bandwidth Or Frequency Error 1 2 57 3 Phase Error in degrees Bandwidth For the above ten ohm crystal the frequency error caused by a one degree phase error 1s 42 114 6 or approximately 0 37 Hz For a one thousand ohm crystal one degree of phase error results in a 37 Hz error and for a ten thousand ohm crystal the frequency error is 370 Hz per degree of phase error Now the effective phase error caused by a non zero quadrature imaginary current is given by the following formula Effective Phase error arctangent imaginary current real current And since current is proportional to conductance Effective Phase error arctangent imaginary conductance real conductance The conductance of a one picofarad capacitor at 5 MHz is 31 4 microsiemens The conductance of a ten ohm crystal at resonance is 100 millisiemens Effective Phase error arctangent 31 4e 6 100e 3 0 018 degrees In other words a one picofarad capacitance unbalance will result in an effective phase error of 5 18 THEORY OF OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE only 0 018 degrees when measuring a ten ohm crystal However when measuring a one thousand ohm crystal the effective phase error will increase to 1 8 degrees and it will increase to 9 degrees when measuring a five thousand
78. ion of Self Assembled Monolayers of Alkyl Thiols on Gold J Am Chem Soc 115 1993 12391 12397 Bott Adrian W Characterization of Films Immobilized on an Electrode Surface Using the EQCM Current Separations 18 3 1999 79 5 Stockel Wolfgang and Schumacher Rolf In situ Microweighing at the Junction Metal Electrolyte Ber Bunsenges Phys Chem 91 1987 345 Gabrielli C Keddam M and Torrei R Calibration of the Electrochemical Quartz Crystal Microbalance J Electrochem Soc 139 9 1991 2657 41 Graeme Andrew Snook Investigation of Solid State Reactions by Electrochemical and Quartz Crystal Microbalance Measurements Ph D Thesis 2000 Department of Chemistry Monash University Clayton 3168 Melbourne Australia and Division of Minerals CSIRO Clayton South 3169 Melbourne Australia under the supervision of Professor Alan Maxwell Bond Monash and Professor Stephen Fletcher CSIRO Available for download from http www bond chem monash edu au theses 48 Bruckenstein S and Shay M Experimental aspects of use of the quartz crystal microbalance in solution Electrochim Acta 30 1985 1295 REFERENCES 12 3 RESEARCH QUARTZ CRYSTAL MICROBALANCE Orata Duke and Buttry Daniel A Determination of Ion Populations and Solvent Content as functions of Redox State and pH in Polyaniline J Am Chem Soc 109 1987 3574 3581 50 Patrice A Noel
79. istry and micro rheology More recent developments have focused on tailoring electrode surface chemistry i e specialized polymer coatings so that these devices can be applied as discriminating mass detectors for many applications including specific gas detection environmental monitoring biosensing and basic surface molecule interaction studies See Section 5 6 for a detail discussion THEORY OF OPERATION 5 5 RESEARCH QUARTZ CRYSTAL MICROBALANCE When the QCM comes in contact with a liquid there is a decrease in frequency that is dependent upon the viscosity and density of the liquid Kanazawa s solution for the change in resonant frequency of the crystal due to liquid loading is shown in Equation 7 3 ap A EL fF Hag Pq f Resonant frequency of unloaded crystal in Hz Equation 7 Where Density of quartz 2 648x 103 kg m shear modulus of quartz 2 947 10 Pa density of the liquid in contact with the electrode in kg m 1 viscosity of the liquid in contact with the electrode in N Sec m Liquid loading also dampens the resonant oscillation of the crystal causing an increase in series resonance resistance R of the crystal Afand AR measurements are both routinely used as independent indicators of mass loading and viscosity at the crystal liquid interface of the QCM resonator during chemical and electrochemical depositions in solution A Butterworth Van Dyke equival
80. ize this effect Polished crystals are required to obtain good agreement between theory and measurement during liquid immersion experiments Polished crystals are also required to obtain measurements reproducibility from crystal to crystal Non polished crystals R 1 8 microns are also available at reduced costs for applications that do not require the accuracy and reproducibility of the polished crystals 4145 CRYSTAL ELECTRODE MATERIALS INFICON s crystals are available in a variety of electrode materials including Gold Platinum Aluminum Silver Titanium etc INFICON also offers Gold electrode crystals with an additional 5102 outer layer to create a hydrophilic surface needed for some biological applications 4 4 5 CRYSTAL THICKNESS INFICON AT cut 1 inch diameter crystals are plano plano Their physical thickness is determined by a frequency constant and their final frequency The frequency constant for an AT cut crystal is 1 668E5 Hz x cm or 65 5 kHz x in Therefore the crystal thicknesses for various frequencies are as follows 5 MHz AT cut thickness 333 microns 0 013 inch 6 MHz AT cut thickness 227 microns 0 0109 inch 9 MHz AT cut thickness 185 microns 0 007 inch 4 1 6 MASS SENSITIVITY The quartz crystal microbalance is an extremely sensitive sensor capable of measuring mass changes in the nanogram cm range with a wide dynamic range extending into the 100 ug cm range Sauerbrey was the first to recognize the p
81. m Male Connector for mating to Crystal Face 1 per Crystal Channel 9 Pin Female Female D sub Computer Interface Cable 1 CD ROM contains computer application software In addition you may have ordered one or more of the accessories listed in Section 1 3 and 1 4 If there is evidence of loss or damage a Notify the carrier or the carrier agent to request inspection of the loss or damage claimed b Keep the shipping containers until it is determined whether or not they are needed to return the equipment to INFICON 2 2 SAFETY PRECAUTION All standard safety procedures associated with the safe operation and handling of electrical equipment must be observed to avoid personal injury and damage to the unit In addition the following guidelines must be observed 221 LINE VOLTAGE The RQCM can be set to operate at one of the four line voltages namely 100 120 220 240 VAC a 50 or 60 Hz line frequency Verify the power entry module is correctly set for your local line voltage 222 GROUNDING A chassis grounding lug is located in the rear panel of next to the power entry module Use a foil or braided wire of 12 AWG or larger to connect the ground lug directly to facility earth ground to provide additional protection against electrical shock 2 2 8 LINE FUSES The RQCM is protected by two miniature Type T fuses They are located inside the power entry module and replaceable The fuse rating is 4 10 amperes 250 V 2 3 SYSTEM CH
82. mistry in A Series of Advances in Electroanalytical Chemistry edited by Allen Bard Marcel Dekker 1991 p 23 33 C Lu and O Lewis Investigation of film thickness determination by oscillating quartz resonators with large mass load J Appl Phys 43 1972 4385 Martin Stephen J Spates James J Wesendorf Kurt O Thomas Schnneider and Robert J Huber Resonator Oscillator Response to Liquid Loading Anal Chem 69 1997 2050 2 Muramatsu H Tamiya Eiichi and Karube Isao Computation of Equivalent Circuit Parameters of Quartz Crystals in Contact with Liquids and Study of Liquid Properties Anal Chem 60 1988 2142 5 Geelhood S J Frank C W and Kanazawa K Transient Quartz Crystal Microbalance Behaviors Compared Journal of the Electrochemical Society 149 2002 H33 H38 2 Yang Mengsu and Thompson Michael Multiple Chemical Information from the Thickness Shear Mode Acoustic Wave Sensor in the liquid Phase Anal Chem 65 1993 1158 27 S J Martin R W Cernosek and J J Spates Sensing Liquid Properties with Shear mode Resonator Sensors in Proceeds from Transducers Eurosensors IX Stockholm Sweden 1995 Kanazawa K Characterization of Operating Behavior of the PLO 10 A Report Submitted to Maxtek Inc by Process Monitor April 2000 p 6 Mark Deakin and Daniel Buttry Electrochemical Applications of the Quartz Crystal Microbalance Anal Chem 61 20 1989 183
83. nce Ratio Hg pP Density of material g cm 44 shear modulus of quartz 2 947 10 g cm s shear modulus of film material in g cm 87 This equation introduces another term into the relationship which is the ratio of the acoustic impedance of quartz to the acoustic impedance of the deposited film The acoustic impedance is associated with the transmission of a shear wave in the deposited mass Notice that the units of the frequency constant for quartz is length time or velocity Also note that if the acoustic impedance ratio is equal to one quartz on quartz then Equation 4 reduces to Equation 3 5 2 THEORY OF OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE 5 3 THICKNESS CALCULATION Film thickness is often the parameter of interest in many QCM applications Thickness can be derived from Equation 4 as follows mal TR cf f where TK thickness of the film in cm Equation 5 Am change in mass per unit area in g cm calculated from the Lu and Lewis equation p density of film material in g cm If the period of oscillation is measured rather than the frequency 1 period can be substituted for frequency resulting in the following equation See INFICON TechNote RTK 101 for details discussion T T TK Pa tan tanz 4 Pr T where 7 Period of unloaded crystal in seconds Equation 6 Period
84. ngs First if the VCO frequency is sitting at its low limit it means the electrode capacitance is over compensated Second in some cases even though the crystal conductance has fallen below the threshold necessary to indicate lock the internal signals are still sufficient to keep the VCO locked to the crystal In that case the PLO really is locked and the VCO frequency will be sitting at the crystal frequency somewhere between its minimum and maximum frequencies If the VCO frequency is sitting at its low limit press and hold the Reset switch and adjust the fine capacitance trimmer a few degrees counterclockwise not more than ten until the Sweep LED begins to flash 3 8 HOOKUP FOR ELECTROCHEMICAL EXPERIMENTS Figure 4 shows a typical connection diagram for an electrochemical QCM using the INFICON RQCM Note that the crystal s front electrode becomes the working electrode when the Crystal OPERATION 3 7 RESEARCH QUARTZ CRYSTAL MICROBALANCE Face Connector on the RQCM is connected to the potentiostat s working electrode port A typical cyclic voltammetric EQCM experiment would involve the application of the electrochemical waveform to the working electrode and the simultaneous measurement of the current flowing through the electrochemical cell and the oscillation frequency and series resonance resistance of the crystal Figure 5 is an example of a typical voltammogram plot obtained from the INFICON RQCM with a PC Thi
85. ode was chosen to ensure a more consistence deposition across the active area of the crystal The exposed area of the front electrode is 0 212 137 mm but the active oscillation region displacement area is limited to the overlapping area of the front and rear electrodes 0 053 in or 34 19 mm CRYSTALS HOLDERS AND FLOW CELL 4 1 RESEARCH QUARTZ CRYSTAL MICROBALANCE WRAP AROUND EXTENDED ELECTRODE FRONT_SIDE REAR_SIDE SENSING ELECTRODE CONTACT ELECTRODE Figure 8 INFICON 1 Inch Diameter Crystals Electrode Configuration The figure below shows a INFICON 1 diameter as seen from the front side MAXTEK 1 CRYSTAL AS SEEN FROM FRONT SIDE Figure 9 INFICON 1 Crystal as Seen From The Front Side 4 1 2 CRYSTAL PARAMETERS Polished one inch diameter crystals that are commonly available for liquid work have the typical values as listed below Type Frequency Electrode Resistance Q Factor Range MHz Material ohms 5 MHz 4 976 5 020 Gold 10 120 000 9 MHz 8 976 9 036 Gold 7 55 000 4 2 CRYSTALS HOLDERS AND FLOW CELL RESEARCH QUARTZ CRYSTAL MICROBALANCE 4 1 3 CRYSTAL SURFACE FINISH Studies have shown that electrode surface roughness can cause large apparent mass loadings due to the liquid that is trapped within pores at the crystal surface INFICO s crystals are optically polished to 50 average surface roughness to minim
86. of the message One byte message length 0 to 249 Indicates the number of data bytes contained in the message One byte checksum 0 to 255 The checksum byte is used for transmission error detection If the RQCM receives a message with an incorrect checksum it will disregard the message The checksum is the compliment of the one byte sum of all bytes from and including the instruction code to the end of the message If the one byte sum of all these bytes is added to the checksum the result should equal 255 If the sum of all bytes occupies more than one byte a single byte checksum can be generated using the expression checksum Sum MOD 256 i e the checksum is the complement of the remainder byte which results from dividing the sum of all bytes by 256 7 9 DATA TYPES There are three data types stored in the ROCM One byte two byte and three byte parameters All data types are stored as integers in binary format with the most significant byte first The one byte data types are ASCII characters numeric values 0 255 or 8 bit registers Some of the multiple byte data types are decimal values stored as integers To convert these values to their decimal equivalent use the following equation Decimal Value Integer Value 10 DP Where DP the value s decimal point position The decimal point positions for all the parameters are constant and are given in tables along with the parameters range 7 10 MESSAGE RECEIVE
87. onance frequency due to a change in the temperature of the crystal at the turnaround point INFICON s 1 inch crystals are optimized for two operating temperatures namely 90 C and 25 C 3 9 3 2 Control The Temperature If operation at or near the crystal s zero turn around point is not possible the operating temperature should be controlled within a degree or a fraction of a degree of its desired value How tightly the temperature should be controlled depends on how far the operating temperature is from the zero turn around point the further away from the turn around point the larger the error For example for 90 C cut crystal about 1 5 Hz C error is expected if operating at 80 C However as much as 5 Hz C error is expected when operating at 60 C 3 9 3 3 Keep the Test Chamber Clean Keep the test chamber clean as any particle attached to the crystal s sensing surface will result in a frequency change 3 9 3 4 Keep a Constant Gas Flow If a gas is used keep the flow constant throughout the experiment The crystal s frequency is also sensitive to changes in pressure which will result if the flow rate is not constant 3 9 4 FOR OPERATION IN LIQUIDS Since the sensor crystal is dampened by the liquid any error in the measurements will be amplified Extra care must be taken to ensure minimal error The sample liquid should be prepared carefully Changes in temperature or the properties of the solvent as well as air bubbles will af
88. otential usefulness of the technology and demonstrate the extremely sensitive nature of these piezoelectric devices towards mass changes at the surface of the QCM electrodes The results of his work are embodied in the Sauerbrey equation which relates the mass change per unit area at the QCM electrode surface to the observed change in oscillation frequency of the crystal Af Crx Am where Af the observed frequency change in Hz C the sensitivity factor of the crystal in Hz ng cm 0 056 Hz ng cm for a 5 MHz crystal 20 C 0 081 Hz ng cm for a 6 MHz crystal 20 C 0 181 Hz ng cm for a 9 MHz crystal 20 C Am the change in mass per unit area in g cm CRYSTALS HOLDERS AND FLOW CELL 4 3 RESEARCH QUARTZ CRYSTAL MICROBALANCE The minimum detectable mass change is typically a few ng cm and limited by the noise specifications of the crystal oscillator and the resolution of the equipment used to measure frequency shifts For example the INFICON RQCM has a frequency resolution of 0 03 Hz 6 MHz therefore its minimum detectable mass change is 0 37 ng cm The Sauerbrey equation relies on a sensitivity factor which is a fundamental property of the crystal Thus in theory the QCM mass sensor does not require calibration This ability to calculate the mass sensitivity from first principles is obviously a very attractive feature of these devices However it is very important to notice that t
89. oughly with deionized water and blow dry with filtered nitrogen gas 4 2 1 6 Polymer Removal To clean polymers from the crystals a combination of plasma cleaning with O2 plasma and piranha solution is recommended However it is best to remove the bulk of the material with 4 8 CRYSTALS HOLDERS AND FLOW CELL RESEARCH QUARTZ CRYSTAL MICROBALANCE organic solvents prior to oxidative cleaning Polymers that are very intractable may be particularly difficult to clean In this case refluxing toluene of Tetrahydrofuran helps to facilitate the removal of the polymer Then the following procedure is recommended A Wash with Organic Solvents Methylene Chloride Toluene or THF to remove most organic material Reflux if needed Wash with Isopropanol and dry Clean in hot piranha 70 sulfuric acid 30 hydrogen peroxide for 1 2 minutes Rinse with DI water Rinse with isopropanol and dry O2 plasma cleaning for 5 minutes or longer if needed Rinse with ethanol mommuonscy O2 plasma clean for 3 minutes Caution Beware when working with piranha solution since it is a strong oxidizer and should not be contacted with any organic solvents Also if you leave the QCM crystal in the hot piranha too long it can leech the chromium or titanium adhesion layer from under the gold leading to delaminating of the gold from the crystal surface Use the crystal as soon as possible or store in a Nitrogen environment 4 2
90. ove the crystal to expose the crystal cavity o Remove both Pogo contact pins from their sockets Use a pair of tweezers or gloved fingernail grab the Pogo head firmly and pull it straight out of its socket o Rinse the holder the crystal cavity and the Pogo sockets generously with deionized water to remove all traces of chemicals and thoroughly blow dry the whole holder using filtered air Ensure all liquids that may have been trapped inside the sockets are removed o Generously rinse the Pogo contact pins with deionized water occasionally squeeze the pins to push out any liquids that may have been trapped inside the pins Thoroughly blow dry the pins using filtered air o Install the Pogo pins back into their sockets Use the tip of a pair of tweezers and push down on each Pogo pins to verify their deflection 4 3 8 CONSIDERATIONS FOR BUILDING YOUR OWN HOLDER You MUST consider the following aspects when building your own crystal holder The holder must be designed so that when a crystal 1s installed the its front electrode sensing electrode is connected to the housing shell of the SMB Crystal Connector on the RQCM see Section 3 3 5 and the rear electrode is connected to the center pin of the SMB Crystal Connector The crystal should be clamped as close as possible to the edge of the crystal to avoid damping of the crystal s oscillations The holder clamping mechanism should have a positive stop to avoid excessi
91. quency The output of the phase detector is fed into an integrator The integrator accumulates the phase error such that any positive phase error causes the integrator output to climb a negative phase causes the integrator output to fall With zero phase error the Integrator output holds steady The integrator output is connected to the VCO Thus if the VCO frequency is initially below the crystal resonant frequency the phase will be positive producing a positive output at the phase detector This causes the Integrator output to climb which causes the VCO frequency to increase When the VCO frequency matches the resonant frequency of the crystal the phase will decrease to zero the phase detector output will go to zero the Integrator output will hold steady and the VCO frequency will be locked to the crystal s resonant frequency If the crystal s resonant frequency moves up or down a phase difference between the crystal voltage and current will develop producing a phase detector output The non zero phase detector output will drive the Integrator output up or down until the phase is zero once again thus keeping the VCO frequency locked to the crystal s resonant frequency Once the frequency of the VCO is locked to the series resonant frequency of the crystal the in phase component at zero phase error there is no out of phase component of the crystal current is demodulated to a DC voltage This voltage is amplified and converted in
92. quency drops below 50 of its uncoated value However for the reasons stated above crystal failures often occur well before a 40 shift in frequency is reached The sensor crystals are considered expendable However a crystal may be reused up to 20 times on average in experiments that don t physically alter the crystal electrode In experiments where a film is deposited the crystal can be stripped using a chemical etchant Care must be taken so only the deposited material is stripped and not the crystal electrodes The amount of times that a crystal can be reused greatly depends on its condition after each experiment or stripping Needless to say careful handling and cleaning of the crystal is required to maximize its re usability Noisy or erratic measurement indicates that the crystal is about to fail It might even be difficult to obtain a stable baseline Spurious signals might become evident in electrochemical QCM experiments Visually traces of consumption and wear can often be seen on the crystal surface Edges of the sensor crystal might become cracked and the deposited film even the electrode starts to show scratches and tears The crystal motional resistance R does reflect the influence of deposited material on the performance of a crystal This resistance is associated with the damping of acoustic waves by the electrodes deposited materials and the supporting structure This resistance increases as more material is being deposite
93. quency of heavily damped crystals the RQCM also tracks the crystal s resistance This provides additional information in the study of lossy films and or viscous solutions The PLO utilizes an internal oscillator referred to as a Voltage Controlled Oscillator VCO to drive the crystal The crystal current is monitored and the frequency of the oscillator is adjusted until there is zero phase between the crystal voltage and current Assuming that the crystal s electrode capacitance has been effectively cancelled this point of zero phase between the crystal current and voltage is the exact series resonant point of the crystal The magnitude of the current at this point is directly proportional to the crystal s conductance This current is monitored by the RQCM and displayed as crystal resistance The PLO contains a phase detector that continuously monitors the phase difference between the crystal s current and voltage At frequencies below the crystals resonant frequency the current leads the voltage and the phase goes to 90 degrees as the frequency separation continues to increase see Figure 19 Above the resonant point the current lags the voltage and the phase go to minus 90 degrees As the frequency increases through the resonant frequency the phase goes from plus 90 through 0 to minus 90 It is interesting to note that the phase angle is 45 degrees when the VCO frequency is one half of the crystal s bandwidth above or below the crystal s resonant fre
94. r short Remove short or replace the defective part No Clear to Send Signal error message when attempting communications with Wrong COMM port number selected Set the correct COMM port number in the Setup Comm Port Setting Menu RS 232 Cable not connected to Connect RS 232 cable to ROCM RQCM Error reading data message Wrong COMM port number Set the correct COMM port Timeout when attempting selected number in the Setup Comm Port communications with ROCM Setting Menu Incorrect RQCM Interface address Set an Interface Address in the Setup Comm Port Settings Menu and click the Send Address button to send to ROCM COMM port not enabled Enable COMM port in PC s BIOS 10 2 TROUBLESHOOTING GUIDE 11 GLOSSARY Conductance Crystal Bandwidth Crystal Holder Crystal Q Kynar Picofarad PLO Quadrature current RQCM RTD Shunt Capacitance Teflon RESEARCH QUARTZ CRYSTAL MICROBALANCE The ability to conduct Conductance is the inverse of resistance Conductance 1 Resistance or Resistance 1 Conductance The units of resistance are Ohms Q V A and the units of conductance are Siemens S A V Abbreviation for chlorinated polyvinyl chloride a resin patented by Goodrich it has excellent mechanical strength and stability over temperature and offers good resistance over a selective range of chemic
95. rect fuse rating Replace line fuse with correct fuse size None of the front panel LED indicators illuminated Blown line fuse Replace fuse Power switch is not on Switch front panel power switch to on No power being applied to unit Check and correct power source and or power cord Wrong line voltage is selected at the rear of RQCM Set line voltage on RQCM rear panel to match with line voltage being used Unable to adjust fine and coarse adjustments to compensate for capacitance The total capacitance of the cable crystal and crystal holder is out of the range of 40 to 200 pfd Adjust cable length to reduce increase its capacitance Unit does not lock onto a frequency when a crystal is installed Crystal fundamental frequency exceeds the frequency range of the crystal channel Verify crystal frequency against crystal channel frequency range To verify the crystal channel frequency ranges press Reset button and observe the output A 3 8 MHz indicates the channel 15 set for 3 8 to 6 MHz A 5 1 MHz indicates a 5 1 to 10 MHz Replace crystal Crystal resistance exceeds the range of 5 and 5 000 Ohms Replace crystal Unit looses lock when crystal is exposed to liquid Total capacitance of the crystal holder and cable changes when going from air to liquid Adjust capacitance compensation with crystal in the liquid Refer to Section 3 4 Unstable
96. red semiconductor material which exhibits a large change in resistance proportional to a small change in temperature A device that has a junction of two dissimilar metals which has a voltage output proportional to the difference in temperature between the hot junction and the lead wires cold junction Abbreviation for Inside Diameter Usually use in specifying a tube size in the form inch 1 D x inch O D where inch are the dimensions Abbreviation for Outside Diameter Usually use in specifying a tube size in the form inch 1 D x inch O D where inch are the dimensions The internal friction of a fluid caused by molecular attraction which makes it resist a tendency to flow Flexible or springy the property of immediately returning to its original size shape or position after being stretched squeezed flexed etc Having or exhibiting both viscous and elastic properties An organic compound found in tissue and that is soluble in nonpolar solvents Water loving attracted to water molecules and polar molecules Water hating not attracted to water molecules or polar molecules A compound containing only the elements carbon and hydrogen Describing a molecule having no separation of centers of positive and negative electrical charge that would make the molecule assume certain orientations more than others in an electric field In chemistry organic refers to a species containing carbon Certain small ions and compounds contain
97. resonant frequency The output of the phase detector is fed into an integrator The integrator accumulates the phase error such that any positive phase error causes the integrator output to climb a negative phase causes the integrator output to fall With zero phase error the Integrator output holds steady The integrator output is connected to the VCO Thus if the VCO frequency is initially below the crystal resonant frequency the phase will be positive producing a positive output at the phase detector This causes the Integrator output to climb which causes the VCO frequency to increase When the VCO frequency matches the resonant frequency of the crystal the phase will decrease to zero the phase detector output will go to zero the Integrator output will hold steady and the VCO frequency will be locked to the crystal s resonant frequency If the crystals resonant frequency moves up or down a phase difference between the crystal voltage and current will develop producing a phase detector output The non zero phase detector output will drive the Integrator output up or down until the phase is zero once again thus keeping the VCO frequency locked to the crystal s resonant frequency Once the frequency of the VCO is locked to the series resonant frequency of the crystal the in phase component at zero phase error there is no out of phase component of the crystal current is demodulated to a DC voltage This voltage is amplified and con
98. s particular experiment involved a 0 1 M solution of CuSO4 in 0 5 M 804 using a 5 MHz 1 inch diameter polished gold coated crystal mounted in a CHC 100 Crystal Holder as the working electrode FINE SMB CABLE COARSE C CRYSTAL SWEEP UNLOCK LOCK caystaL a POTENTIOSTAT SMB TO BNC RQCM PARTIAL LJ ADAPTOR FRONT VIEW a NOT REQUIRED FOR WORKING ELECTRODE E TO RQCM ANALOG INPUT pp TO ROCM ANALOG INPUT di NOTE THESE CONNECTIONS ARE REQUIRED FOR THE ROCM TO BE ABLE TO DATA LOG MASS AND CURRENT VERSUS POTENTIAL THE ROCM MUST BE EQUIPED WITH AN OPTIONAL DATA ACQUISITION CARD CRYSTAL HOLDER CHC 100 SHOWN COUNTER ELECTRODE REFERENCE ELECTRODE Figure 4 Typical Connections For Electrochemical QCM Experiment 3 8 OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE w Name echemi Run Number 16 E DLACO IPIE 690 0 o a xu 4 f H 4 1 4 Curent Wi 0 474 84 9 31 78 ao CDS 4 1498 22 L v 2 4 51 4 AAA ISA A RRA A A 6400 0 300 Potential 0 300 en sms Plat All Pw Graphs prin Text Naw Filo Heip Exit Figure 5 Typical Voltammogram Plot Obtained Using th
99. s resistance This provides additional information in the study of lossy films and or viscous solutions The PLO utilizes an internal oscillator referred to as a Voltage Controlled Oscillator VCO to drive the crystal The crystal current is monitored and the frequency of the oscillator is adjusted until there is zero phase between the crystal voltage and current Assuming that the crystal s electrode capacitance has been effectively cancelled this point of zero phase between the crystal current and voltage is the exact series resonant point of the crystal The magnitude of the current at this point is directly proportional to the crystal s conductance This current is monitored by the RQCM and displayed as crystal resistance The PLO contains a phase detector that continuously monitors the phase difference between the crystal s current and voltage At frequencies below THEORY OF OPERATION 5 15 RESEARCH QUARTZ CRYSTAL MICROBALANCE the crystals resonant frequency the current leads the voltage and the phase goes to 90 degrees as the frequency separation continues to increase see Figure 19 Above the resonant point the current lags the voltage and the phase go to minus 90 degrees As the frequency increases through the resonant frequency the phase goes from plus 90 through 0 to minus 90 It is interesting to note that the phase angle is 45 degrees when the VCO frequency is one half of the crystal s bandwidth above or below the crystal s
100. s thermistor has a range of 0 to 150 C The use of a thermistor provides high accuracy measurements within its temperature range or when long leads are required 8 2 2 RTD INPUT The RTD has a range of 0 to 600 C The use of the RTD is for the measurements in the higher temperature ranges The RTD input is designed to use an RTD conforming to the European standard curve with an alpha of 0 00385 for the Calendar van Dusen equation and a resistance of 100 ohms 0 C The RTD is connected as a four wire element using a pair of wires for excitation and pair of wires to sense the voltage across the element This configuration should be continued all the way to the probe for maximum accuracy A single shielded cable with two twisted pairs or two shielded twisted pair cables should be used 8 2 3 THERMOCOUPLE INPUT The Type T Thermocouple input uses true internal cold junction compensation For accurate measurements thermocouple grade copper and constantan wire must be used from the thermocouple to the rear panel thermocouple connector Figure 31 shows the rear panel thermocouple connector The mating connector is an Omega NMP T M included with each Data Acquisition Card or equivalent If it is desired to use shielded thermocouple wire which is recommended the shield drain wire can be connected to the RTD or thermistor shield pin The Type T Thermocouple has a range of 0 to 371 C The use of a thermocouple is recommended in oxidizing reducing
101. soft lint free cloth will scratch the crystal CRYSTALS HOLDERS AND FLOW CELL 4 7 RESEARCH QUARTZ CRYSTAL MICROBALANCE 4 2 1 CRYSTAL CLEANING The surface properties of the sensor crystal determine the interaction of sample material with the surface Therefore the developments of proper procedures for cleaning are required to obtain meaningful and reproducible measurements This section provides the basic information you need to develop a cleaning procedure suited to your sample surface preparation CAUTION When developing a cleaning procedure always perform a test run on a crystal before committing to a larger batch cleaning Follow the crystal handling guidelines throughout the cleaning process to protect the crystal quality Avoid using high pH cleaners since they will etch the crystal surface 4 2 1 1 General Cleaning For general purpose applications such as electrochemistry and liquid or viscoelastic film experiments it is usually sufficient to use ultrasonic cleaning method to clean the crystals in a solution of non basic detergent in deionized water Immediately rinse liberally with deionized water and dry in a gentle flow of filtered nitrogen gas 4 2 1 2 Organic hydrocarbon contaminants UV ozone treatment is a powerful tool for removing hydrocarbon impurities which have been adsorbed from the ambient air This method utilizes irradiation with ultra violet light that breaks up the organics on the surface of th
102. ss determination with piezoelectric quartz crystal resonators J Vac Sci Technol 12 1 1975 578 Rodahl and Kasemo B Frequency and dissipation factor responses to localized liauid deposits on a QCM electrode Sensors and Actuators B37 1996 111 116 Ward M D and Delawski E J Radial Mass Sensitivity of the Quartz Crystal Microbalance in Liquid Media Anal Chem 63 1991 886 10 Cernosek R W et al Analysis of the radial dependence of mass sensitivity for Modified electrode quartz crystal resonators Anal Chem 50 1998 237 Lu Chih shun Monitoring And Controlling Techniques For Thin Film Deposition Processes AVS Course Material published under the auspices of The Education Committee American Vacuum Soiety 1981 p 64 65 l Vig J R UV Ozone Cleaning of Surfaces in Treatise on Clean Surface Technology Vol 1 ed By K L Mittal Plenum Press 1987 p 1 26 Cohen Y Levi S Rubin S and Willner I Modified Monolayer electrodes for electrochemical and PZ analysis Novel immunosensor electrodes J ElectroAnal Chem 417 1996 65 Minunni M Guilbault G G and Hock B Quartz Crystal microbalance as a biosensor Anal Lett 28 1995 749 Patel Rupa Zhou R Zinszer K Josse F and Cernozek R Real time Detection of Organic Compounds in Liquid Environments Using Polymer coated Thickness Shear Mode Quartz Resonators Anal Chem 72 2
103. stance Change vs Wt Glycerol 5 4 4 DECAY LENGTH OF SHEAR WAVE IN LIQUID As mentioned in the section above when an oscillating crystal is in contact with a liquid there will be a decrease in the resonant frequency and an increase in the motional resistance The decrease in the resonant frequency is caused by the additional mass of the vibrating liquid The increase in motional resistance is caused by the power dissipation of the shear wave that radiates into the liquid The decay length of the shear wave into the liquid is defined by Equation 9 Where Lp Decay length in m Density of the liquid in contact with the electrode in kg m 77 Viscosity of the liquid in contact with the electrode in kg m sec 5 8 THEORY OF OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE Angular frequency at series resonance 27f For example the decay length for a 5 Mhz crystal in water at 20 C is 2 5x10 m 0 25 microns 5 5 DISSIPATION METHOD The Dissipation Method is an alternate way of measuring the crystal to determine the properties of the film and or the liquid In this method the crystal is driven at its resonant frequency by an oscillator then the crystal shorted and both the resonant frequency and the oscillation decay time are measured The crystal dissipation is related to Q and R as follows Equation 10 D 1 Q u Where D Dissipation Q Quality Factor R resistance in Q L indu
104. t of this document without permission is unlawful First Edition March 2002 Revision A May 2002 Revision B October 2002 Revision C December 2002 Second Edition Revision D June 2003 Revision E July 2004 Revision F October 2004 Revision G August 2005 Revision H November 2005 A WARNING All standard safety procedures associated with the safe handling of electrical equipment must be observed Always disconnect power when working inside the controller Only properly trained personnel should attempt to service the instrument INFICON CONFORMITY This is to certify that this equipment designed and manufactured by INFICON Inc Two Technology Place East Syracuse NY 13057 USA meets the essential safety requirements of the European Union and is placed on the market accordingly It has been constructed in accordance with good engineering practice in safety matters in force in the Community and does not endanger the safety of persons domestic animals or property when properly installed and maintained and used in applications for which it was made Equipment Description Applicable Directives Applicable Standards CE Implementation Date Authorized Representative Research Quartz Crystal Microbalance Thin Film Deposition Controller including the SO 100 Oscillator Package 73 23 EEC as amended by 93 68 EEC LVD 89 336 EEC as amended by 93 68 EEC EMC 2002 95 EC RoHS EN 61010 1 200
105. tance the computer would send the following message Chr 255 Chr 254 Chr 1 Chr 1 Chr 3 Chr 6 Chr 0 Chr 0 Chr 245 The RQCM will then send one message every 50 milliseconds that it 12 bytes long and contains 6 bytes of data The first four bytes of data is sensor period and the next two bytes are sensor resistance Data logging is stopped by sending the following message Chr 255 Chr 254 Chr 1 Chr 1 Chr 3 Chr 0 Chr 0 Chr 0 Chr 251 3 Configure Data Acquisition Board Code 12 This instruction allows the computer to configure the input range and temperature units of the RQCM s Analog Input Temperature card The following table shows the byte configuration for this message COMPUTER INTERFACE 7 7 RESEARCH QUARTZ CRYSTAL MICROBALANCE Byte Description Length Range bytes 6 Temperature Configuration 1 0 7 Total Bytes 6 Each inputs voltage range and filter frequency can be independently configured There are four voltage ranges and two frequency ranges The available values are as follows Input Voltage Range Filter Freq Code Volts Hertz 0 0t05 1 1 0 to 10 1 2 5 1 3 10 1 4 0t05 8 5 0 to 10 8 6 5 8 7 10 8 The temperature configuration byte sets the units for the three temperature inputs A value of zero selects Fahrenheit and a value of seven selects Celsius Example To set inputs 1 through 5 for 0 to 5
106. tance is at a maximum when the plates are fully meshed and a minimum when rotor plates are above the stator plates and not meshed As the capacitor is rotated clockwise it goes through a full cycle from maximum to minimum and back to maximum Or depending on where you start it may go first toward a minimum then to a maximum and then back toward a minimum To avold confusion always turn the fine adjustment clockwise as we approach the desired capacitance and we want the capacitance to be decreasing The coarse adjustment is a rotary switch Like the fine adjustment it goes from its minimum to its maximum then back to its minimum capacitance value in a full rotation The difference is that it has 16 positive stops Observe the notch on the switch Figure 3 The coarse adjustment is at its minimum capacitance when the notch is pointing straight upward zero position The capacitance is increased with each stop as the switch is rotated clockwise It reaches maximum capacitance at the 15 stop one stop before returning to the zero position The RQCM is setup for a standard INFICON crystal holder and cable from the factory so you should not have to change the course adjustment Simply connect the cable and crystal holder to OPERATION 3 5 RESEARCH QUARTZ CRYSTAL MICROBALANCE the SMB connector labeled Crystal but don t install a crystal If the Sweep LED is flashing press and hold the Reset button and then turn the
107. the PLO results in a 0 44 Hz frequency error for a SMHz crystal with a Q of 100 000 For a 5 MHz crystal with a Q of 10 000 the error is 10 time greater or 4 4 Hz per degree Frequency Error deg df f 1 360 Q 5 16 THEORY OF OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE 5 7 3 FREQUENCY ERROR DUE TO IMPERFECT CAPACITANCE CANCELLATION The effect of imperfect electrode capacitance cancellation can also be viewed as an equivalent phase error This error is directly proportional to crystal resistance The equivalent phase error due to a non zero shunt capacitance equal to 1 pfd is one degree for a crystal with a series resistance of 556 O Since the equivalent phase error is proportional to the crystal resistance a 1 pfd residual capacitance error will result in a 10 degree equivalent error for a sensing crystal with a resistance of 5 56 KO Polar Plot of Crystal Conductance IMAGINARY AXIS DIRECTION OF INCREASING FREQUENCY 250 SIEMENS 4 CRYSTAL WITH 1 pfd NET SHUNT CAPACITANCE N EFFECTIVE PHASE ERROR DUE TO NON ZERO SHUNT CAPACITANCE REAL AXIS 1 2 3 4 5 x 100 uSIEMENS 4KQ CRYSTAL WITH 0 pfd NET SHUNT CAPACITANCE Figure 25 Equivalent Phase Error Due to Imperfect Capacitance Cancellation THEORY OF OPERATION 5 17 RESEARCH QUARTZ CRYSTAL MICROBALANCE 5 8 FREQUENCY ERRORS DUE TO IMPERFECT CAPACITANCE CANCELLATION There are two reasons that proper capacitance cancellation is
108. tion of temperature Effective capacitance due to the electrodes on the crystal This is the unwanted capacitance we try to cancel out along with the capacitance in the cable and the holder of course while adjusting the Fine amp Coarse capacitance cancellation on the Crystal Measurement Channel s on the RQCM DuPont Company s registered trademark of Perfluoroalkoxy Fluorocarbon Resin a class of Teflon that offers excellent inertness to aqueous acid and aqueous alkaline superior resistance over a wide range of pH Visit www dupont dow com for more information Voltage Controlled Oscillator An oscillator circuit designed so that the output frequency can be controlled by applying a voltage to its control or tuning port GLOSSARY 11 1 Viton RTD Thermistor Thermocouple Viscosity Elastic Viscoelastic Lipid Hydrophilic Hydrophobic Hydrocarbon nonpolar Organic UVO cleaning Ultrasonic cleaning 11 2 GLOSSARY RESEARCH QUARTZ CRYSTAL MICROBALANCE DuPont Dow Elastomers registered trademark of Fluoroelastomer offers superior mechanical properties and resistance to aggressive fuels and chemicals well known for its excellent heat resistance Visit www dupont dow com viton for more detailed information Resistance temperature detector A device that senses temperature by measuring the change in resistance of a material A temperature sensing element composed of sinte
109. to equilibrium and establish a baseline prior to making measurements OPERATION 3 11 RQCM RESEARCH QUARTZ CRYSTAL MICROBALANCE HOLIMS Y3IMOd YOLV IANI WALSAS JINVIVEOYIIN TVLSAUI NOOY Naisn ZLUVND vis O O XYL 887 333 SNLVLS NOILVOINNWWOD YILNANOD 15 T3NNVHO LNSWSYNSVAWN WLSAYO TVNOLLAO 8 Z STANNVHO LNSAWSYNSVAW WLSAYO 519 axy 6 5 Figure 6 Front Panel 3 12 OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE Y 30 10H 3505 Y YOLOATAS 39V L10A HOLO3NNOO HOLO3NNOO 3 1VW NS A Nid SZ Javi LYOd NOISINDOV Viva YOLI3INNO9 8NS O Nid 6 LYOd S8t SH HO ZEZ SY IVNOLLAO 887 3331 TWNINYAL GNNOYSD IVNOLLAO LYOd AY VI NOLLISINDIV V LVG H LIM S3INOO YOLIINNO9 TIANODONY3HL L LN3WdO T3A3G 301103 1404 AYVTIXNV Figure 7 RQCM Rear Panel 3 13 OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE 4 CRYSTALS HOLDERS AND FLOW CELL An essential part of the ROCM system is the sensing crystal Careful handling of both the crystal and the crystal holder must be observed to ensure proper and reproducible measurements Furthermore the sensing crystal the crystal holder and the connecting cable must be orientated and connected correctly in order for the RQCM to work properly This is especially true if you
110. to resistance value which the RQCM outputs to the computer OPERATION 3 1 RESEARCH QUARTZ CRYSTAL MICROBALANCE 3 2 UNDERSTANDING AND SETTING UP A CRYSTAL MEASUREMENT CHANNEL The RQCM can have up to three independent crystal measurement channels Each channel has a crystal input three status LED s fine and course capacitance adjustments a reset switch and a crystal face connection Refer to Figure 2 3 3 FRONT PANEL DESCRIPTION 3 3 1 LOCK INDICATOR The green Lock LED is on when the oscillator is locked on a crystal s resonant frequency 3 3 2 UNLOCK INDICATOR The Red Unlock LED will be on whenever the oscillator is not locked on a crystal 3 83 8 SWEEP INDICATOR The Yellow Sweep LED flashes each time the frequency ramp is reset to its low starting point In normal operation the sweep light will only flash while adjusting the capacitance compensation The Sweep LED will not light when locked on a crystal 3 3 4 RESET SWITCH The Reset switch should be pressed while adjusting the capacitance compensation This switch forces the VCO to its lowest frequency independently of the Integrator output The Reset switch also forces the Lock LED on thus turning off the quadrature current injection which is required for proper capacitance cancellation adjustment The equivalent of about 1 5 pfd of capacitance is added as quadrature current to insure that the VCO ramps up in frequency when not locked onto a crystal The quadrat
111. ue to the coupling of the shear mode oscillation with the temperature dependent viscosity and density of the fluid For experiments in liquid phase in which the frequency is to be monitored over long periods of time the temperature must be controlled to at least 0 1 C and preferably better In electrochemical experiments this is often achieved with temperature controlled baths and jacketed cells It is CRYSTALS HOLDERS AND FLOW CELL 4 5 RESEARCH QUARTZ CRYSTAL MICROBALANCE always good practice to wait at least 30 minutes before performing any accurate measurements after the crystal comes in contact with a new medium This allows the crystal to come to equilibrium with the medium If temperature control is not possible or practical attempts should be made to measure the temperature of the solution around the crystal during the experiments and perform temperature compensation In short each RQCM user must determine the effect of temperature on the experiments being performed and either control the temperature accordingly or measure the temperature and compensate for it Freq Change vs Temp INFICON AT cut for 90C Delta Frequency Hz N 0 10 20 30 40 50 60 70 80 90 100 110 120 Temperature Figure 10 Frequency vs Temperature of INFICON 1 AT Cut Crystal for 90 4 6 CRYSTALS HOLDERS AND FLOW CELL RESEAR
112. until it s snug CRYSTALS HOLDERS AND FLOW CELL 4 11 RESEARCH QUARTZ CRYSTAL MICROBALANCE 4 3 2 HOLDER CARE AND HANDLING With a robust design INFICON crystal holders require little care However the crystal holder is in direct contact with the sensor crystal and your experiment environment Thus care must be taken to ensure its cleanliness eliminating any contaminants that may react with the crystal or the experiment media The following guidelines are recommended for general handling of the holders Always keep the holder clean and dry when not in use Always use clean room grade gloves while handling the holder and its components Never handle the holder with bare hands as human skin oils may deposit on it and react with your experiment Always ensure that your holder is compatible with your experiment environment Never submerge the holder unassembled or without a crystal Never submerge the holder pass its terminal connector at the end of the rod Always rinse the holder generously with deionized water and thoroughly blow dry using filtered air after each experiment This 1s especially important if the holder has been exposed to oxidizing acids Always act fast in the event that liquids or chemicals have entered the crystal cavity in the holder Immediately clean the holder using the following procedure x CRYSTALS HOLDERS AND FLOW CELL RESEARCH QUARTZ CRYSTAL MICROBALANCE o Rem
113. ure current is turned off as soon as a lock is detected 3 3 5 CRYSTAL CONNECTOR The SMB connector labeled Crystal provides connections to the crystal When used with a INFICON crystal holder the center pin connects to the crystal s rear electrode and the connector housing connects to the crystal s front electrode 3 3 6 CRYSTAL FACE CONNECTOR The Crystal Face connector provides a direct connection to the crystal s front electrode Note that the mating connector 2 5 mm male plug provided with each Crystal Measurement Channel must be used for proper connection When the mating connector is inserted the crystal face electrode is galvanically transformer isolated from earth ground allowing a potential to be applied Use this connection to connect the crystal face electrode to the working electrode of a potentiostat or galvanostat for electrochemical experiments When this connection is not in use the crystal face electrode is grounded to minimize effects of capacitance that may couple to crystal face electrode in non electrochemical experiments 3 2 OPERATION RESEARCH QUARTZ CRYSTAL MICROBALANCE 3 3 6 1 Crystal Face Mating Connector The mating connector to the Crystal Face Connector is a 2 5 mm male plug The plug carries two contacts the tip and the sleeve see Figure 1 However only the tip contact is used to connect to the working electrode of a potentiostat You can solder the working electrode wire directly to the tip
114. ut quartz resonator J Appl Phys 68 5 1990 1993 5 Iddo Ben Dov and Itamar Willmer Piezoelectric Immunosensors for Urine Specimens of Chlamidia trachomatis Employing QCM Microgravimetric Analysis Anal Chem 69 1997 3506 50 Lasky Steven J Buttry Daniel Sensors Based Biomolecules Immobilized on the Piezoelectric Quartz Crystal Microbalance Chemical Sensors and Microinstrumentation 0 32387 SEA Hengerer K sslingerl J Decker S Hauck1 I Queitsch2 H Wolf and S D bel2 Determination of Phage Antibody Affinities to Antigen by a Microbalance Sensor System BioTechniques 26 956 964 May 1999 12 4 REFERENCES
115. ve clamping force on the crystal If the crystal is to be used in a conductive fluid or conductive gas the rear electrode must be sealed from the conductive environment to avoid an electrical short between the electrodes The electrodes should be designed so the rear electrode and the electrodes contacts can be sealed Only the front electrode should be exposed The connecting cable must be coaxial all the way from SMB on the RQCM on up to the crystal The shield of the coaxial must connect to the front electrode and the center conductor must connect to the rear electrode of the crystal In addition the coaxial cable must be free of kinks knots etc to avoid unbalanced capacitance in the cable Note that a one foot of well balance RG174A U coaxial cable has approximately 29 picofarads The total capacitance of the crystal the crystal holder and the cable must be within the RQCM s capacitance compensation limits between 40 and 200 pfd 4 4 FLOW CELL The FC 550 Flow Cell is designed to be used with any of INFICON s 100 series crystal holders The FC 550 is made from Kynar The cell has two stainless steel inlet and outlet tubes with a 047 x 062 O D compatible with 0 062 I D tubing A Viton O ring provides sealing between the cell and the face of the sensor crystal The cell is used in place of the Crystal Retainer Ring Once installed in a probe it creates a flow chamber of approximately 0 1 mL CRYSTALS HOLDERS AND
116. verted into resistance value which the RQCM outputs to the computer 571 FREQUENCY ERRORS The first thing we want to know regarding the performance of the crystal measurement is What is the magnitude of the frequency error we can expect from the crystal measurement portion of the ROCM In any oscillator and sensing crystal system the error in the frequency measurement is a function of both the oscillator and the sensing crystal The same is true for phase locked loops Any phase error will introduce a frequency error and this frequency error will be inversely proportional to the sensing crystal s Q These errors are over and above any change in crystal frequency due to stress temperature adsorption and humidity changes There are four important parameters that determine the frequency error of the PLO and sensing crystal system or indeed any oscillator and sensing crystal system The first two the zero phase error and the electrode capacitance cancellation errors are characteristics of the PLO The second two are characteristics of the crystal the Q of the crystal and the conductance l resistance of the crystal 5 7 2 FREQUENCY ERROR DUE TO PHASE ERROR Given some finite zero phase error the resulting frequency error depends on the sensing crystal s Q the higher the Q the lower the error For phase errors below 10 degrees the frequency error is 0 087 PPM per degree for crystals with a Q of 100 000 Thus a one degree phase error in
117. ystal holder Improper seating of the crystal large mechanical coupling between the crystal and the holder Thermal input Radiation from evaporation source radiation from substrate heater bombardment by charge particles energy released by condensates Stress Thermal stress stress release in the deposited materials Temperature See section 4 1 9 for data on frequency versus temperature for INFICON s crystals Other factors that can affect stability are humidity shock vibration and change in pressure Controlling those conditions is a must to insure accurate measurements of small mass changes over long periods of time 4 1 8 CRYSTAL LIFE EXPECTANCY It is difficult to predict the useful life of a crystal since it depends on many factors Some of these factors are The quality of the quartz The amount of deposited material The stress generated in the crystal due to deposited material 4 4 CRYSTALS HOLDERS AND FLOW CELL RESEARCH QUARTZ CRYSTAL MICROBALANCE The acoustic losses in the deposited material The design of the oscillator circuitry Other aspects that affect the crystal life include the type of the deposited material spitting of source material resulting in non uniform films film flakes that landed on the crystal s active area and of course physical damage to the crystal such as chipping cracking or peeling of the electrode etc In general a sensor crystal can be used until its fre

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