[AMBIENT ATOMIC/MAGNETIC FORCE MICROSCOPY MANUAL]

Transcription

1 [AMBIENT ATOMIC/MAGNETIC FORCE MICROSCOPY MANUAL] VER: 2.0

2 TABLE OF CONTENT 1. INTRODUCTION THEORY OF OPERATION Principle of Atomic Force Microscope (AFM) INSTALLATION & OPERATION INSTALLATION Installing the PC Workstation & AFM Controller AFM OPERATION Preparing the AFM Adjusting the Cantilever, the Laser and the Photodetector Contact Mode AFM operation Approaching the Surface Scanning the Surface NON-CONTACT AFM MODE Approaching the Surface Scanning the Surface DYNAMIC MODE AFM Approaching the Surface Scanning the Surface SCANNING TUNNELLING MICROSCOPY (STM) Approaching the Surface Scanning the Surface MAGNETIC FORCE MICROSCOPE (MFM) Approaching the Surface Scanning the Surface ELECTROSTATIC FORCE MICROSCOPE (EFM) Approaching the Surface Scanning the Surface LIQUID CELL Introduction Liquid Cell Assemblies The Liquid Cell Cantilever Holder The Liquid Cell Sample Holders O-ring

3 The Liquid Cell Scanner Installation of Liquid Cell Operation Loading Cantilever into Cantilever Holder Sample Preparation & Sample Holder Laser Alignment Loading Liquid and Laser Realignment Contact Mode Operation in Liquid Cell Dynamic Mode Operation in Liquid Cell Care of the Liquid Cell Parts EPDM O-ring Specifications Chemical Compatibility of PEEK AFM CONTROL ELECTRONICS INTRODUCTION POWER SUPPLY CARD Test/Calibration Procedure SCAN DAC CARD Test & Calibration Procedure HV AMP Test & Calibration Procedure DAC CARD Test & Calibration Procedure MICROCONTROLLER & A/D CARD Test & Calibration Procedure CONTROLLER CARD PHASE LOCKED LOOP(PLL) CARD Test & Calibration Procedure TAPPING MODE NONCONTACT MODE SPARE A/D CARD Test & Calibration Procedure PCI BUS DIGITAL I/O CARD INSTALLING AND RUNNING SPM PROGRAM ADJUSTMENT OF CANTILEVER, FOCUS AND PHOTODEDECTOR APPROACHING THE SURFACE SCANNING THE SURFACE CONTACT MODE APPLICATIONS

4 9. FFM MODE APPLICATIONS DYNAMIC MODE APPLICATIONS NON-CONTACT MODE APPLICATIONS MFM MODE APPLICATIONS EFM MODE APPLICATIONS STM MODE APPLICATIONS LITHOGRAPHY LIQUID CELL APPLICATIONS AFM CABLE SETS

5 4 1. Introduction The NanoMagnetics Atomic Force Microscope (AFM) system uses a laser beam to measure forces between microfabricated cantilevers and sample. A single piezo tube is used for scanning the sample in XYZ directions under computer control through the AFM Control Electronics & SPM Software. The microscope can be operated in the following modes: Contact Mode AFM Lateral Force Microscope (LFM) Dynamic Mode AFM & Phase Imaging Non-contact Mode AFM Closed Cell Liquid AFM Magnetic Force Microscope (MFM) Electrostatic Force Microscope (EFM) Scanning Tunnelling Microscopy (STM) Piezo Response Force Microscopy (PRFM) Conductive AFM (CAFM) AFM Lithography and Nanomanipulation Multi Frequency Force Microscopy Kelvin Probe Force Microscopy (KPFM) Nanoindentation The system also enables to change the sample temperature from 10 C to +100 C with water cooling, if temperature control option is ordered. 1.1 THEORY OF OPERATION PRINCIPLE OF ATOMIC FORCE MICROSCOPE (AFM) In the Atomic Force Microscopes (AFM), atomic forces between a sharp needle and sample surface are measured using a spring as shown in Figure 1-1. In practice the spring is actually a microfabricated silicon or silicon nitride cantilever with an integrated tip as displayed in the Figure 1-2 and the deflection of the spring is measured using a laser beam.

6 5 grooves Tip Sample Figure 1-1: Concept of Atomic Force Microscope Figure 1-2: Microfabricated Silicon AFM cantilevers & their tip shapes

7 6 A red diode laser beam is focused at the back of the cantilever and the reflected beam hits a quadrant photodiode to measure the cantilever deflections as shown in Figure 1-4. The forces between tip and the sample deflect the cantilever and this change the position of laser beam on photodetector. The use of quadrant photodetector enables to measure formal as well as lateral forces action on the cantilever beam. The resultant photocurrents at the detector quadrants are amplified with a sensitive preamplifier and processed to give Normal Force (F NORMAL ), Lateral Force (F LATERAL ) and Total Force (F TOTAL ) from the cantilever. The normal force is kept constant by adjusting the sample-tip separation using a piezoceramic element (PZT) driven by a feedback circuit and high voltage amplifiers. As the sample is scanned in X and Y directions using the AFM Control Electronics, the feedback circuit moves the sample up and down keeping the force constant. Then the Z (x,y) position of the specimen, measured from the piezo voltage gives the topography of the surface. Figure 1-3: The NanoMagnetics AFM

8 7 Figure 1-4: Principle of Atomic Force Microscopy The NanoMagnetics AFM is shown in Figure 1-3. The system is composed of the AFM Head which measures the cantilever displacements using a laser beam bounce method, XYZ motorised stages, Granite base, vibration isolation table, the acoustic/thermal isolating cabinet, AFM Control Electronics, PC and SPM Control Software. AFM Control Electronics is a modular unit built into a 19 rack mountable base unit and replaceable 30mm or 60mm wide, 220x100mm Eurocard modules with low noise backpanel as shown in Fig The SPM Control Software operates under Windows Vista/XP/2000/NT/98 operating systems and is written in C#. The system is supplied with the User Kit, which includes all the necessary small tools (screwdrivers, tweezers, cantilever/sample holders, cantilevers,, silver paint etc.) and most of the consumables to run the microscope.

9 8 Figure 1-54: NanoMagnetics AFM Electronics 2. Installation & Operation 2.1 INSTALLATION Please unpack the AFM box, AFM Control Electronics, User Kit, and PC Workstation & Dual 19 Monitors. Please check that all the components are delivered in good condition. If there is a broken or damaged piece; please inform the shipping agent and NanoMagnetics Instruments within 7 days to claim the damage from the insurance. The following additional items are required to run the system efficiently: ~ 3m 2 workspace for the AFM and PC ~ 1m 2 clean and dry workbench ~ x50-x500 Optical microscope with top illumination and digital/video camera to inspect the probes. A clean & relatively dust free lab environment A two channel oscilloscope, preferably a digital one, like Tektronix TDS1002

10 9 A Digital Multimeter with capacitance function An ultrasonic cleaner Pure acetone, isopropanol & a couple of beakers INSTALLING THE PC WORKSTATION & AFM CONTROLLER 1. Setup the PC Workstation nearby the AFM System. First of all the Digital I/O card should be installed. Please follow the steps below to install the Digital I/O card. 2. Switch the PC workstation off and open the cover of the computer case. Then insert the PCI Digital IO card into one of empty PCI slots firmly, screw it tight. Figure 2-1: AFM Control Electronics to PC Connections 3. Attach & screw one end of the Digital IO cable to Card installed into the PC and the other end to the D-37 connector input of the MicroA/D card of AFM Control Electronics. 4. Switch the PC on. Install the PCI Digital IO card program, INSTACAL ver5.44, from the CD supplied. You need to restart the PC after installation. 5. Run Instacal Program

11 10 The PCI-DIO24 board is completely plug-and-play. Perform the following procedure to install the hardware: 1. Turn the computer OFF, open it up, and insert the board into any available PCI slot. 2. Close up the computer and turn it ON. 3. Some operating systems, such as Windows XP or Vista, automatically detects the board as it starts up. If the board s configuration file is already on the system, it loads without user interaction. If the configuration file is not detected, insert the disk containing it at the prompt. The required file is on the InstaCal disk or CD shipped with the board. The required file(s) automatically loads, and the PCI board displays in the Device Manager under DAS components. If you are installing from CD and your system has the auto-run feature enabled, the installation dialog opens and you can then select the option to install InstaCal and/or the Universal Library. If auto-run is not enabled, use Explorer to navigate to the CD drive and double click on the \Product\Disk1\Setup.exe program or click Start\Run and type: D:\Product\Disk1\Setup.exe (assuming your CD drive is D:\); then click OK. Be sure to restart your computer after the initial software installation, and before running InstaCal. Run the InstaCal program to test your board and configure it for run-time use. By configuring the board, you add information to the configuration file, cb.cfg. This file is used by the Universal Library as well as third-party data acquisition packages that use the Universal Library to access the board. To run InstaCal, follow the steps below: 1. Open the program group folder (Measurement Computing by default) you created 2. Select the InstaCal shortcut

12 11 Figure 2-2: Opening Instacal Program You can also run the program by double-clicking on the file "instacal32.exe" in your installation directory. If your plug-and-play board has been properly detected by the system, InstaCal displays a Board Detection dialog box. It lists the board you are installing, and any other Measurement Computing plug-and-play boards that have been detected in the system. This dialog gives you the option of adding any or all of the listed boards to the configuration file (cb.cfg). Once installed, the properties (configuration) of the board may be changed by double-clicking on the board name. For plug-and-play boards, many of the properties are set by the system and cannot be changed through InstaCal. After running the software installation program, installing your board in the PC, and setting your board configuration with InstaCal, test the installation. Select the Test menu and then select the board you want to verify. Select the type of test to perform and follow the instructions provided. If you do not receive the expected results: Make sure you have connected the correct pins according to the connector diagram in your hardware user's guide. Go back through the installation procedure and make sure you have installed the board according to the instructions in the manual. If required, select CALIBRATE from the InstaCal main menu. The procedure is self-documented. Calibration of auto-calibrate boards requires no external equipment. Calibration of most other boards requires a precision voltage source and/or a precision voltmeter. After installation, delete the demo Board #0 from. If you wait a while the Windows XP operating system will identify the PCI-DIO card and assign its ID number.

13 12 Install the SPM Control Program from the CD supplied. Make sure that the correct operating voltage is set for the AFM Control Electronics. The mains voltage can be selected by changing the position of the switch at the mains inlet of the AFM Control Electronics. Please use a flat bladed screw driver to extract the switch and rotate it to the voltage appropriate for your lab; 100/110/220/240Vac. 2.2 AFM OPERATION PREPARING THE AFM Please keep the AFM under its protective cover when it is not in use. Please handle the piezo tube scanner with care. Always try to keep it clean and be careful while performing operations on the tube since there are very brittle piezo ceramics those might be damaged. Never apply any excess force on the sample holder piezo or the probe holder. These parts are very delicate and can break easily. Most of the problems occur after the user gets acquainted with the system and starts omitting the steps, or not being careful enough due to confidence. Always think twice before doing something. Please do not perform the delicate operations when you are under stress First unpack the acoustic isolation platform and assemble it. Then place the vibration isolation table on it with the transport screws are intact. Then, position the granite base block on the vibration isolation platform. Then mount the Z-stage bracket and the motorised Z-stage on the granite base block. Then fix the XY motorised or manual stage on the granite block as shown in

14 13 the Figure 2-3. The Scan unit should then be mounted on the XY stage. After the AFM is mounted on the granite base plate firmly, please connect the AFM cable set supplied as described in Section 17. Then measure the capacitances of the Scanner piezo electrodes from the BNC connectors, North, South, East & West. Check that the capacitances are close to the values listed in Table 2-1. Here, C x denotes the corresponding pole for the scan piezo (i.e. C N is the capacitance for the North pole.) These values are measured at the AFM BNC connectors and include the BNC cables capacitances. Scan piezo capacitances are between the electrode and the ground. If they are not close within 10% of the listed values, there can be an electrical or mechanical damage to the piezos or cables. Using the Digital Multi Meter (DMM) supplied, check the insulation resistance of the scanner piezo electrodes to the chassis: they all should be >100MΩ. C N C S C E C W 7.0nF 7.0nF 7.0nF 7.0nF Table 2-1: Capacitance values for the AFM Scanner

15 14 Acoustic Isolation Cabinet Marble Base Vibration Isolation Table Chiller Control Electronics Z Motorized Stage AFM Head Scan Head XY Motorized Stage Figure 2-3: Assembly of the NanoMagnetics AFM

16 ADJUSTING THE CANTILEVER, THE LASER AND THE PHOTODETECTOR Select an appropriate cantilever and mount it at the cantilever holder as you press the pin at the bottom to release the cantilever holder spring as shown in Figure 2-4. Place the cantilever holder at the AFM Head and observe the cantilever is visible by the integrated video microscope. If not pull the holder out and shift the cantilever chip carefully until you see the cantilever from the top view video camera clearly. Figure 2-4: Mounting the cantilever (marked blue) on the cantilever holder

17 16 Switch the laser on and adjust the laser power to 10%. Place a piece of white paper under the AFM head so that you can see the shadow of the cantilever with the laser light by adjusting the X and Y screws as shown in the Figure 2-5, position the laser spot at the end of the cantilever. At this point you should see the reflection of the laser spot from the cantilever end at the video camera and the shadow of the cantilever at the paper below. The X screw will move the laser spot along the X axis and the Y screw will move the laser spot along the Y axis. Figure 2-5: Adjusting the laser spot position on the cantilever Now, you should be able to collect some light at the photodetector. Double click the photodiode adjust dialog at the SPM Control Software and open the dialog which measures the position of the laser spot on the quadrant photodetector as shown in Figure 2-6.

18 17 Figure 2-6: Photodetector Adjustment Dialogue By playing with the photodetector screws as shown in Figure 2-7, roughly position the photodetector at the center of the laser beam bounced from the cantilever. Then look at the computer screen and try to bring the dot at the centre of the crossed hairline as shown in Figure 2-6, by playing with the screws Y & Z. As you do this, the F TOTAL should be incrased the Y screw will move the photodetector along the Y axis and the Z screw will move the photodetector along the Z axis. After completing the laser & photodetector adjustment the AFM is now ready to run in the desired mode of operation. Figure 2-7: Adjusting the photodetector position

19 CONTACT MODE AFM OPERATION In the contact mode of operation, the cantilever is in physical contact with the surface. For ultimate sensitivity and low damage to the sample, a soft cantilever microfabricated from Silicon or SiNi with very low spring constant must be used. The adjustable parameters are contact force and the feedback loop gain of the AFM Control Electronics. When the cantilever is mounted, laser and photodetector are aligned than select the Contact Mode of operation from the software. All the connections are done automatically in the AFM Control Electronics by the SPM Software. Enter the desired Contact Force at the software. Enter the desired Normal Force value which is equal to Ftotal value. Adjust the Loop gain to APPROACHING THE SURFACE Now position the sample on the sample holder and enter Commands > Approach or click the approach shortcut and reach the approach bar. If the microscope is far from the surface, coarse approach should be selected and the AFM head should be first brought close to the sample by coarse, fast and medium steps. When you see the cantilever and its reflection, then you can control the distance to the surface with the video system, start the automatic approach sequence simply by clicking automatic approach as shown in Fig This will bring the cantilever closer to the sample, checking the set Normal Force value at each step. It pulls the tip before making a step and then releases it. It stops making steps if a desired normal force is established and V z is below a certain set value, 10 V.

20 19 Figure 2-8: Approach window When you find the surface the automatic approach sequence will stop. If necessary you can approach with a few fine slow steps manually. But this must be done very carefully to avoid a large step, which may crash the cantilever in to the sample to be scanned. When the V Z signal is stable you can start to scan. But it is better if the scanner piezo position V Z is around 0 V, so the scanner can move back and forth to maintain the set current value easily SCANNING THE SURFACE When the desired V Z is achieved, you can now start the scan. Depending on the area you want to image, the scan offset values may have to be changed. While changing these values it is much safer to pull the sample sliders few steps back and then change the offsets. Then you can find the surface again. For the maximum area, the scan offsets must be (-28.µm,-28. µm). Scan process is activated Commands > Scan Images as shown in Figure 2-9 or you can click the scan shortcut button.

21 20 Figure 2-9: Starting the Scan Image Dialog You will see a dialog box as shown in Figure Choose the Normal Scan option, enter all the desired scan parameters at the dialog box and push Start Scan button. The dialog box is closed, forward and backward scan windows are opened for every channel chosen as shown in Figure Moreover corresponding line cross-section displays are also opened and displayed for chosen channel. Figure 2-10: Scan Image Dialog

22 21 The images are automatically saved in the specified directory. If you enter a full path you can save the images anywhere you like. if you only give a name then the pictures will be saved under the images directory that exists under the installed path of the SPM Program. The scan lines acquired by the microscope are displayed one by one, building up the images slowly. Forward scans will be displayed on the left side and backward scans on the right as shown in Figure You can stop the scan anytime you want by pressing the Stop Scan button. If you want to start a new image or take the microscope out, first pull the sample back by steps. Then close the SPM Program and switch off the electronics Never switch the electronics off before retracting the cantilever and closing the SPM Software Figure 2-11: Scanning the image line by line

23 NON-CONTACT AFM MODE In the non-contact AFM (nc-afm) mode of operation, the cantilever is NOT in physical contact with the surface. For ultimate sensitivity and low damage to the sample, stiff cantilevers microfabricated with silicon must be used. In Nc-AFM the cantilever is always vibrated at its resonance frequency using a Digital Phase Locked Loop(PLL). The cantileversample forces change the resonance frequency of the cantilever and PLL circuit measures the Frequency Shift (ΔF) and RMS Amplitude of the vibrations. The feedback circuit keeps the ΔF constant. The adjustable parameters are Excitation amplitude, desired Frequency Shift and the feedback loop gain of the AFM Control Electronics. When the AFM is fully adjusted, select the Non-Contact AFM Mode of operation from the software. All the connections are done automatically in the AFM Control Electronics by the AFM Software. We first need to find the resonance frequency of the free cantilever and set the PLL. Open the PLL window which opened when you chose the non-contact mode. Push the Auto-Tune button or select Commands> Auto-Tune and thanfrequency Sweep window will be appear as shown in Figure First select start/stop frequencies to 0 Hz & 400,000Hz, respectively. Adjust the increment to 1000 Hz to then press start. After finding the resonance, we need to fine tune it with smaller increments. Then select Center/span part and maximum value which is found at previous step will be written on Center Freq. part automatically as shown in Figure Insert ~ Hz for the Span value and ~1-10 to Increment, then press `start` button again. After the centre frequency is determined, check the phase values which are Start = 0, stop = 360 and increment =1.0 then press start. After the optimum phase value is found for the PLL, click FINISH. Or don t do all of this and just push Auto they all will be done automatically. Figure 2-12: Starting the PLL Dialog

24 23 Figure 2-13: PLL Auto-Tune window Enter the desired f value 40 Hz.Decrease the loop gain to APPROACHING THE SURFACE Now position the sample on the sample holder and enter Commands > Approach or click the approach shortcut and reach the approach bar. If the microscope is far from the surface, coarse approach should be selected and the AFM head should be first brought close to the sample by coarse, fast and medium steps. When you see the cantilever and its reflection, then you can control the distance to the surface with the video system, start the automatic approach sequence simply by clicking automatic approach as shown in Figure This will bring the cantilever closer to the sample, checking the set ΔF value at each step. It pulls the tip before making a step and then releases it. It stops making steps if a desired normal force is established and V z is below a certain set value, 10V.

25 24 Figure 2-14: Approach window Figure 2-15: EXT IN & Vz signals

26 25 As you approach the sample automatically you will observe the signals like in the Figure Figure 2-16: FNX10 and dither signals FNx10 and dither will give sinusoidal signals as shown on the monitor of the oscilloscope as shown in Figure When you find the surface the automatic approach sequence will stop. If necessary you can approach with a few fine slow steps manually. But this must be done very carefully to avoid a large step, which may crash the cantilever in to the sample to be scanned. If the ΔF value changes so much you can increase the desired ΔF or decrease the loop gain. When the V Z signal is stable you can start to scan. But it is better if the scanner piezo position V Z is around 0V, so the scanner can move back and forth to maintain the set current value easily SCANNING THE SURFACE When the desired V Z is achieved, you can now start the scan. Depending on the area you want to image, the scan offset values may have to be changed. While changing these values it is much safer to pull the sample sliders few steps back and then change the offsets. Then you can find the surface again. For the maximum area, the scan offsets must be (-28.5µm,-28.5 µm). Scan process is activated Commands > Scan Images as shown in Figure 2-17 or you can click the scan shortcut button

27 26 Figure 2-17: Starting the Scan Image Dialog You will see a dialog box as shown in Figure Choose the Normal AFM Scan option, enter all the desired scan parameters at the dialog box and push Start Scan button. The dialog box is closed, forward and backward scan windows are opened for every channel chosen as shown in Figure Moreover corresponding line cross-section displays are also opened and displayed for every forward and backward image of chosen channels. Figure 2-18: Scan Image Dialog The images are automatically saved in the specified directory. If you enter a full path you can save the images anywhere you like. if you only give a name then the pictures will be saved under the images directory that exists under the installed path of the SPM Program. The scan lines acquired by the microscope are displayed one by one, building up the images slowly. Forward scans will be displayed on the left side and backward scans on the right as shown in Figure You can stop the scan anytime you want by pressing the Stop Scan button. If you want to start a

28 27 new image or take the microscope out, first pull the sample back by steps. Then close the SPM Program and switch off the electronics Never switch the electronics off before retracting the cantilever and closing the SPM Software DYNAMIC MODE AFM Figure 2-19: Scanning the image line by line In the Dynamic Mode AFM operation, the cantilever is occasionally in physical contact with the surface. For ultimate sensitivity and low damage to the sample, stiff cantilevers microfabricated from Silicon must be used. In dynamic mode AFM the cantilever is vibrated at its free resonance frequency using a fixed frequency signal source. The cantilever-sample forces change the oscillation amplitude and the relative phase of the resultant oscillations. The system ( It is actually the PLL circuit with the PLL Loop Turned off) measures the Phase Shifts (ΔF) and RMS

29 28 Amplitude of the vibrations. The feedback circuit keeps the RMS Amplitude constant. The adjustable parameters are excitation amplitude and the feedback loop gain of the AFM Control Electronics. When the AFM is fully adjusted, select the Dynamic Mode AFM of operation from the software. All the connections are done automatically in the AFM Control Electronics by the AFM Software. We first need to find the resonance frequency of the free cantilever and set the PLL. Open the PLL window opened when you chose the non-contact mode. Push the Auto-Tune button or select Commands> Auto-Tune and than Frequency Sweep window will be appear as shown in Figure First select start/stop frequencies to 0 Hz & 400,000Hz, respectively. Adjust the increment to 1000 Hz to then press start. After finding the resonance, we need to fine tune it with smaller increments. Then select Center/span part and maximum value which is found at previous step will be written on Center Freq. Part automatically as shown in Figure Insert ~ Hz for the Span value and ~1-10 Hz to Increment, then press `start` button again. After the centre frequency is determined,. Check the phase values which are Start = 0, stop = 360 and increment =1 then press start. After the optimum phase value is found for the PLL, click FINISH. Or don t do all of this and just push Auto they all will be done automatically. Figure 2-20: Starting the PLL Dialog

30 29 Figure 2-21: PLL Auto-Tune window Enter the desired RMS value as ~50% of the free oscillation amplitude: Amplitude = RMS value * Adjust the Loop gain to APPROACHING THE SURFACE Now position the sample on the sample holder and enter Commands > Approach or click the approach shortcut and reach the approach bar. If the microscope is far from the surface, coarse approach should be selected and the AFM head should be first brought close to the sample by coarse, fast and medium steps. When you see the cantilever and its reflection, then you can control the distance to the surface with the video system, start the automatic approach sequence simply by clicking automatic approach as shown in Figure This will bring the cantilever closer to the sample, checking the set ΔF value at each step. It pulls the tip before making a step and then releases it. It stops making steps if a desired normal force is established and V z is below a certain set value, 10V.

31 30 Figure 2-22: Motor Control window Figure 2-23: FNX10 and dither signals

32 31 FNx10 and dither will give sinusoidal signals as shown on the monitor of the oscilloscope as shown in Figure When you find the surface the automatic approach sequence will stop. If necessary you can approach with a few fine slow steps manually. But this must be done very carefully to avoid a large step, which may crash the cantilever in to the sample to be scanned. If the ΔF value changes so much you can increase the desired ΔF or decrease the loop gain. When the V Z signal is stable you can start to scan. But it is better if the scanner piezo position V Z is around 0V, so the scanner can move back and forth to maintain the set current value easily SCANNING THE SURFACE When the desired V Z is achieved, you can now start the scan. Depending on the area you want to image, the scan offset values may have to be changed. While changing these values it is much safer to pull the sample sliders few steps back and then change the offsets. Then you can find the surface again. For the maximum area, the scan offsets must be (-28.5µm,-28.5 µm). Scan process is activated Commands > Scan Images as shown in Figure 2-24 or you can click the scan shortcut button Figure 2-24: Starting the Scan Image Dialog You will see a dialog box as shown in Figure Choose the Normal AFM Scan option, enter all the desired scan parameters at the dialog box and push Start Scan button. The dialog box is closed, forward and backward scan windows are opened for every channel chosen as shown in Figure Moreover corresponding line cross-section displays are also opened and displayed for every forward and backward image of chosen channels.

33 Before start the scanning click the null phase button on PLL window Figure 2-25: Scan Image Dialog The images are automatically saved in the specified directory. If you enter a full path you can save the images anywhere you like. As a default if you only give a name then the pictures will be saved under the IMG directory that exists under the installed path of the AFM Program. The scan lines acquired by the microscope are displayed one by one, building up the images slowly. Forward scans display on the left side and backward scans on the right as shown in Figure You can stop the scan anytime you want by pressing the Stop Scan button. If you want to start a new image or take the microscope out, first pull the sample back by steps. Then close the SPM Program and switch off the electronics.

34 Never switch the electronics off before retracting the cantilever and closing the SPM Software Figure 2-26: Scanning the image line by line

35 SCANNING TUNNELLING MICROSCOPY (STM) Figure 2-27: Scanning Tunnelling Microscopy STM operation is based on a quantum mechanical phenomenon, electron tunnelling. In this method, a biased tip scans the surface while the tunnel current is present between tip and conducting sample as shown in Figure The tunnel current is an exponential function of tipsample separation and decays by a factor of ten for every one Angstrom (0.1nm) increase in the separation. A piezoelectric ceramic scanner is used to move the tip/sensor in 3 dimensions, XY and Z. These ceramic materials change their dimensions if an electric field is applied to them. NanoMagnetics Instruments Ltd. AFM is designed mainly for constant current mode STM operation. In constant current mode, the tunnelling current is kept constant, using a feedback circuit while we scan the surface, as shown in Figure The feedback circuit generates appropriate voltages (V z ) to the scanner piezo, which moves the tip with picometer resolution up and down, in order to keep the tunnel current constant. As the tip/sensor is scanned by applying appropriate voltages, V x and V y to the x and y piezoelectric scanner, the topography Z(x,y) of the sample is obtained by recording V z (x,y). The feedback circuit keeps the tunnel current constant. The adjustable parameters are tunnel current, V BIAS and the feedback loop gain of the AFM Control Electronics. When the AFM is fully

36 35 adjusted, select the STM Mode of operation from the software. All the connections are done automatically in the AFM Control Electronics by the AFM Software. Enter the desired tunnel current value as 0.4nA, V BIAS = - 0.1V and adjust the Loop gain to APPROACHING THE SURFACE Now position the sample on the sample holder and enter Commands > Approach or click the approach shortcut and reach the approach bar. If the microscope is far from the surface, coarse approach should be selected and the AFM head should be first brought close to the sample by coarse, fast and medium steps. When you see the cantilever and its reflection, then you can control the distance to the surface with the video system, start the automatic approach sequence simply by clicking automatic approach as shown in Figure This will bring the cantilever closer to the sample, checking the set Normal Force value at each step. It pulls the tip before making a step and then releases it. It stops making steps if a desired normal force is established and V z is below a certain set value, 10 V. Figure 2-28: Approach window

37 36 To approach the surface safely, the Vz and It(out) signals should be observed from the oscilloscope as shown in Figure Figure 2-27: It(out) & Vz signals As you approach the sample automatically you will observe the signals like in the Figure When you find the surface the automatic approach sequence will stop.. If necessary you can approach with a few fine slow steps manually. But this must be done very carefully to avoid a large step, which may crash the cantilever in to the sample to be scanned. When the V Z signal is stable you can start to scan. But it is better if the scanner piezo position V Z is around 0V, so the scanner can move back and forth to maintain the set current value easily SCANNING THE SURFACE When the desired V Z is achieved, you can now start the scan. Depending on the area you want to image, the scan offset values may have to be changed. While changing these values it is much safer to pull the sample sliders few steps back and then change the offsets. Then you can find the surface again. For the maximum area, the scan offsets must be (-20 µm,-20 µm). Scan process is

38 37 activated Commands > Scan Images as shown in Figure 2-30 or you can click the scan shortcut button Figure 2-30: Starting the Scan Image Dialog You will see a dialog box as shown in Figure Choose the Normal AFM Scan option, enter all the desired scan parameters at the dialog box and push Start Scan button. The dialog box is closed, forward and backward scan windows are opened for every channel chosen as shown in Figure Moreover corresponding line cross-section displays are also opened and displayed for every forward and backward image of chosen channels. Figure 2-31: STM tip scanning on the surface

39 38 Figure 2-32: Scan Image Dialog The images are automatically saved in the specified directory. If you enter a full path you can save the images anywhere you like. if you only give a name then the pictures will be saved under the images directory that exists under the installed path of the SPM Program. The scan lines acquired by the microscope are displayed one by one, building up the images slowly. Forward scans will be displayed on the left side and backward scans on the right as shown in Figure You can stop the scan anytime you want by pressing the Stop Scan button. If you want to start a new image or take the microscope out, first pull the sample back by steps. Then close the SPM Program and switch off the electronics Never switch the electronics off before retracting the cantilever and closing the SPM Software

40 39 Figure 2-33: Scanning the image line by line 2.6 MAGNETIC FORCE MICROSCOPE (MFM) Magnetic Force Microscopy (MFM) is a secondary imaging mode derived from dynamic mode that maps magnetic force gradient above the sample surface. In MFM measurements cantilevers must be magnetic coated and sample must have magnetic properties. Cantilever can be made of single crystalline silicon, silicon dioxide (SiO 2 ), or silicon nitride (Si 3 N 4 ). The Si 3 N 4 cantilever-tip are usually more durable and have smaller restoring force constants (k).tips are coated with a thin (< 50 nm) magnetic film (such as Ni or Co), usually of high coercivity so that the tip magnetic state (or magnetization M) does not change during imaging. Forward scan is used for to determine the topography, while the backward scan is used to determine magnetic force gradient in the lift-off mode as shown in Figure When the tip scans the surface of a sample at so close distances (< 100 nm), not only magnetic forces are sensed, but also atomic and electrostatic forces as well. Thus, the lift height method helps to enhance the magnetic contrast by doing the following;

41 40 First, the topographic profile of each scan line is measured. That is, the tip is brought into close proximity of the sample to take AFM measurements. The magnetized tip is then lifted further away from the sample. On the second pass, the magnetic signal is extracted. The phase change is measured to determine the magnetic forces in backward scan by means of a digital PLL. Figure 2-34: MFM Principle The adjustable parameters are excitation amplitude, desired RMS, lift of height and the feedback loop gain of the AFM Control Electronics. When the AFM is fully adjusted, select the MFM Mode of operation from the software. All the connections are done automatically in the AFM Control Electronics by the SPM Software. We first need to find the resonance frequency of the free cantilever and set the PLL. Open the PLL window which opened when you chose the MFM mode. Push the Auto-Tune button or select Commands> Auto-Tune and than Frequency Sweep window will be appear as shown in Figure First select start/stop frequencies to 0 Hz & 400,000Hz, respectively. Adjust the increment to 1000Hz to then press start. After finding the resonance, we need to fine tune it with smaller increments. Then select Center/span part and maximum value which is found at previous step

42 41 will be written on Center Freq. part automaticly as shown in Figure Insert ~ Hz for the Span value and ~1-10 to Increment, then press `start` button again. After the centre frequency is determined, check the phase values which are Start = 0º, stop = 360º and increment =1.0º then press start. After the optimum phase value is found for the PLL, click FINISH. Or don t do all of this and just push Auto they all will be done automaticly. Figure 2-35: Starting the PLL Dialog Figure 2-36: PLL Auto-Tune window Enter the desired RMS value as ~50% of the free oscillation amplitude: Amplitude = RMS value * Adjust the Loop gain to 999.

43 APPROACHING THE SURFACE Now position the sample on the sample holder and enter Commands > Approach or click the approach shortcut and reach the approach bar. If the microscope is far from the surface, coarse approach should be selected and the AFM head should be first brought close to the sample by coarse, fast and medium steps. When you see the cantilever and its reflection, then you can control the distance to the surface with the video system, start the automatic approach sequence simply by clicking automatic approach as shown in Figure This will bring the cantilever closer to the sample, checking the set RMS value at each step. It pulls the tip before making a step and then releases it. It stops making steps if a desired normal force is established and V z is below a certain set value, 10V. Figure 2-37: Approach window

44 43 Figure 2-38: FNX10 and dither signals FNx10 and dither will give sinusoidal signals as shown on the monitor of the oscilloscope as shown in Figure When you find the surface the automatic approach sequence will stop. V Z for its stability. If necessary you can approach with a few fine slow steps manually. But this must be done very carefully to avoid a large step, which may crash the cantilever in to the sample to be scanned When the V Z signal is stable you can start to scan. But it is better if the scanner piezo position V Z is around 0V, so the scanner can move back and forth to maintain the set current value easily SCANNING THE SURFACE When the desired V Z is achieved, you can now start the scan. Depending on the area you want to image, the scan offset values may have to be changed. While changing these values it is much safer to pull the sample sliders few steps back and then change the offsets. Then you can find the surface again. For the maximum area, the scan offsets must be (-20 µm, -20 µm). Scan process is activated Commands > Scan Images as shown in Figure 2-39 or you can click the scan shortcut button

45 44 Figure 2-39: Starting the Scan Image Dialog You will see a dialog box as shown in Figure Choose the Normal AFM Scan option, enter all the desired scan parameters at the dialog box. On Scan Parameters tab enter the lift off as a V or nm and push Start Scan button. The dialog box is closed, forward and backward scan windows are opened for every channel chosen as shown in Figure Moreover corresponding line cross-section displays are also opened and displayed for every forward and backward image of chosen channels. Figure 2-40: Scan Image Dialog The images are automatically saved in the specified directory. If you enter a full path you can save the images anywhere you like. if you only give a name then the pictures will be saved under the images directory that exists under the installed path of the SPM Program. The scan lines acquired by the microscope are displayed one by one, building up the images slowly. Forward scans will be displayed on the left side and backward scans on the right as shown in Figure 2-41.

46 45 You can stop the scan anytime you want by pressing the Stop Scan button. If you want to start a new image or take the microscope out, first pull the sample back by steps. Then close the SPM Program and switch off the electronics Never switch the electronics off before retracting the cantilever and closing the SPM Software Figure 2-41: Scanning the image line by line

47 ELECTROSTATIC FORCE MICROSCOPE (EFM) Electrostatic Force Microscopy (EFM) is a secondary imaging mode derived from dynamic mode that maps conductive and nonconductive gradient above the sample surface. The strength of the electric interaction between the tip and the sample is adjustable in EFM by applying a voltage between the sample surface and the tip. In EFM measurements cantilevers must be conductive coated, they can be made of single crystalline silicon, silicon dioxide (SiO 2 ), or silicon nitride (Si 3 N 4 ). The Si 3 N 4 cantilever-tip are usually more durable and have smaller restoring force constants (k).tips are coated with a thin (< 50 nm) conductive film (such as Cr/Pt), usually of high coercivity so that the tip electrostatic state (or electric dipole moment p) does not change during imaging. Forward scan is used for to determine the topography, while the backward scan is used to determine electrostatic state in the lift-off mode as shown in Figure When the tip scans the surface of a sample at so close distances (< 100 nm), not only electrostatic forces are sensed, but also atomic and magnetic forces as well. Thus, the lift height method helps to enhance the electrostatic contrast by doing the following; First, the topographic profile of each scan line is measured. That is, the tip is brought into close proximity of the sample to take AFM measurements. The conductive tip is then lifted further away from the sample. On the second pass, the magnetic signal is extracted. The phase change is measured to determine the electrostatic forces in backward scan by means of a digital PLL.

48 47 Figure 2-42: EFM Principle The adjustable parameters are excitation amplitude, desired RMS, lift of height, bias voltage and the feedback loop gain of the AFM Control Electronics. When the AFM is fully adjusted, select the EFM Mode of operation from the software. All the connections are done automatically in the AFM Control Electronics by the SPM Software. We first need to find the resonance frequency of the free cantilever and set the PLL. Open the PLL window which opened when you chose the EFM mode. Push the Auto-Tune button or select Commands> Auto-Tune and than Frequency Sweep window will be appear as shown in Figure First select start/stop frequencies to 0 Hz & 400,000Hz, respectively. Adjust the increment to 1000Hz to then press start. After finding the resonance, we need to fine tune it with smaller increments. Then select Center/span part and maximum value which is found at previous step will be written on Center Freq. part automaticly as shown in Figure Insert ~ Hz for the Span value and ~1-10 to Increment, then press `start` button again. After the centre frequency is determined, check the phase values which are Start = 0, stop = 360 and increment =1.0 then press start. After the optimum phase value is found for the PLL, click FINISH. Or don t do all of this and just push Auto they all will be done automaticly.

49 48 Figure 2-43: Starting the PLL Dialog Figure 2-44: PLL Auto-Tune window Enter the desired RMS value as ~50% of the free oscillation amplitude: Amplitude = RMS value * Adjust the Loop gain to APPROACHING THE SURFACE Now position the sample on the sample holder and enter Commands > Approach or click the approach shortcut and reach the approach bar. If the microscope is far from the surface, coarse approach should be selected and the AFM head should be first brought close to the sample by coarse, fast and medium steps. When you see the cantilever and its reflection, then you can control the distance to the surface with the video system, start the automatic approach sequence simply by clicking automatic approach as shown in Figure This will bring the

50 49 cantilever closer to the sample, checking the set RMS value at each step. It pulls the tip before making a step and then releases it. It stops making steps if a desired normal force is established and V z is below a certain set value, 10V. Figure 2-45: Approach window

51 50 Figure 2-46: FNX10 and dither signals FNx10 and dither will give sinusoidal signals as shown on the monitor of the oscilloscope as shown in Figure When you find the surface the automatic approach sequence will stop. V Z for its stability. If necessary you can approach with a few fine slow steps manually. But this must be done very carefully to avoid a large step, which may crash the cantilever in to the sample to be scanned When the V Z signal is stable you can start to scan. But it is better if the scanner piezo position V Z is around 0V, so the scanner can move back and forth to maintain the set current value easily SCANNING THE SURFACE When the desired V Z is achieved, you can now start the scan. Depending on the area you want to image, the scan offset values may have to be changed. While changing these values it is much safer to pull the sample sliders few steps back and then change the offsets. Then you can find the surface again. For the maximum area, the scan offsets must be (-20 µm,-20 µm). Scan process is activated Commands > Scan Images as shown in Figure 2-47 or you can click the scan shortcut button

52 51 Figure 2-47: Starting the Scan Image Dialog You will see a dialog box as shown in Figure Choose the Normal AFM Scan option, enter all the desired scan parameters at the dialog box. On Scan Parameters tab enter the lift off as a V or nm and push Start Scan button. The dialog box is closed, forward and backward scan windows are opened for every channel chosen as shown in Figure Moreover corresponding line cross-section displays are also opened and displayed for every forward and backward image of chosen channels. Figure 2-48: Scan Image Dialog The images are automatically saved in the specified directory. If you enter a full path you can save the images anywhere you like. if you only give a name then the pictures will be saved under the images directory that exists under the installed path of the SPM Program. The scan lines acquired by the microscope are displayed one by one, building up the images slowly. Forward scans will be displayed on the left side and backward scans on the right as. You can stop the scan

53 52 anytime you want by pressing the Stop Scan button. If you want to start a new image or take the microscope out, first pull the sample back by steps. Then close the SPM Program and switch off the electronics Never switch the electronics off before retracting the cantilever and closing the SPM Software LIQUID CELL INTRODUCTION Apart from the other microscopes, the most prominent feature of AFM is its ability to operate under aqueous solutions. To achieve this goal, a liquid cell is necessary. There are two types of liquid cells which are open liquid cells (open bucket type) and closed liquid cells (sealed type). Obviously, imaging in liquids is not as easy as imaging at air. Liquid conditions imply some difficulties such as performing good sealing, avoiding air bubbles, providing immobilization of the sample properly. In addition, since the laser beam detection method is used, the beam cannot simply pass through a liquid-air interface because it will be refracted all over the cell due to the movement of the liquid surface. On the other hand, imaging sample under liquids eliminates attractive forces due to surface tension which enables the sample surface to be imaged with a minimum of cantilever tip force. This could be an advantage when imaging biological specimens and soft materials. The procedure for imaging samples under liquid is the same as that for Contact Mode and Dynamic Mode AFM in air; however special hardware is used to keep liquid in the cell. Moreover, little adjustments should be done to adjust laser beam as it pass through air-liquid interfaces.

54 LIQUID CELL ASSEMBLIES THE LIQUID CELL CANTILEVER HOLDER The Liquid Cell Cantilever Holder consists of stainless steel (SS) body, PEEK cantilever holder attached to SS body with three screws, angular prism and two micro tubes attached to PEEK cantilever holder as shown in Figure In order to supply liquid inlet and outlet to the cell flexible tubes (OD2mm; ID1mm) are used which are also compatible to peristaltic micro pumps. The angular prism is placed over cantilever mount to prevent liquid evaporation and undesiredscatterings caused by an unstable liquid surface. Liquid removal hole Injection tubes O-ring Cantilever groove Liquid inlet hole Figure 2-49: Liquid Cell Cantilever Holder THE LIQUID CELL SAMPLE HOLDERS There are three types of the liquid cell sample holders made of PEEK. In the design inner groove is for o-ring and outer groove is a pool for unexpected leaks coming from inside of the cell after flood.

55 54 There is a micro tube attached near of the pool for drainage with syringe. The Cap-like sample holder can be put on to the scanner easily after sample preparation outside. There are four magnets allows it mount onto the scanner tightly. The different kind of sample holders let you to prepare your sample in different heights as shown in Figure If you select appropriate sample holder for your sample height you do not need to use extra substrate or adhesive material to increase sample height. O-ring groove Leak pool Micro tube Front side Back side Substrate thickness 1 mm 0.5mm Substrate thickness 1.3mm Substrate thickness 0.5 mm Figure 2-50 : Liquid Cell Sample Holders

56 O-RING To minimize the dynamics of fluids during imaging and prevent evaporation o-ring is preferred to use as shown in Figure The elasticity of o-ring is important for the system. The scanner is constituted scan piezo tube (PZT) and its movement is determented during imaging by applying forces which is formed by the wedge of o-ring between AFM head and sample holder. The used o-ring allowed scanner easy movement during scanning which affects resolution. 20 shore A EPDM O-ring Liquid Cell Sample holder with o-ring Figure 2-51: Liquid Cell Sample Holders and o-ring THE LIQUID CELL SCANNER The liquid cell sample holder is also convenient for the applications in air. On the liquid cell scanner, there are 4 magnets which are engaged with those under the sample holders. It consists of a piezo tube and the sample holder attached on the piezo tube as shown in Figure There are many wire connections inside of the scanner. In the case of liquid leakage, short circuit may occur and the scanner may become useless. As a precaution there is a second pool around sample holder for extra leaks, however some amount of liquids may spill through the gap

57 56 between inner side of the pool and the sample holder. If you observe any spillage from the pool into the scanner, TURN the power OFF as quick as possible. Standard Holder Liquid removal micro tubes Pool for overflows from the liquid cell sample holder. Figure 2-52: Liquid cell compatible AFM scanner head Before start to use scanner, uncover the filmstrip on the surface of the sample holder. 2. Use tissues to protect the microscope assemblies during liquid transfers against spilage

58 INSTALLATION OF LIQUID CELL A. Change the Standard Cantilever Holder with the Liquid Cell Cantilever Holder. B. Change the scanner with the liquid cell scanner. C. Place the liquid cell sample holder and the o-ring on the liquid cell scanner. Figure 2-53 : The vertical projection of the liquid cell cantilever holder, the o-ring and the liquid cell sample holder OPERATION Do not attempt to operate with standard cantilever holder in liquid environment. Standard cantilever holders have small cables and dither piezo which may cause short circuit when exposed to liquids Generally, imaging in liquid has same procedures as that in air; however, special hardware is utilized to contain the fluid. In addition, laser refractions must be minimized with minor adjustments while the laser beam passes through air-liquid interfaces. Unwanted air bubbles are also cause trouble if they are floating on the projection of the laser beam during imaging. In the

59 58 case of dynamic mode operation, resonance frequency will be changed by damping forces of liquids. In this case to be able to find correct resonance frequency of cantilever in liquid is more challenging than those in air Always be careful about spillage from liquid cell after inserting liquid into the liquid cell. The sample scanner, XY motorized stage and connectors should not be exposed with liquids. Spillage may result in damage of these parts of AFM. In the case of spillage, turn the electronics power off immediately and dry all affected surfaces carefully Standard Cantilever Holder Liquid Cell Cantilever Holder Figure 2-54: Cantilever holders for air and liquid applications

60 LOADING CANTILEVER INTO CANTILEVER HOLDER Select appropriate cantilever and place it on liquid cell cantilever holder. However in this case two tweezers are used to load cantilever onto the holder. One is used for rising PEEK spring to be able to place cantilever on the groove with the help of the other one. Be careful of giving damage to the surface of the glass with the tip of the tweezers. Figure 2-55: Loading cantilever

61 SAMPLE PREPARATION & SAMPLE HOLDER Choose appropriate liquid cell sample holder according to your sample height. Then attach sample in the middle of the sample holder as strong as that it will not be detached in the liquid. Adhesive tapes or epoxy can be used for sample mounting in the cell. According to your sample height you may need to stick two or more tapes on each other. Then liquid cell sample holder ready to be placed on scanner. There are four magnets which are embedded under sample holders and on the scanner. Liquid Cell sample holder must be placed on the scanner as these magnets attract each other Be sure that magnets under liquid cell sample holder are engaged with magnets on the scanner. 2- There are three types of liquid cell sample holders which can be selected according to the sample thickness. These holders differ in sample pucks

62 61 Figure 2-56: Profiles of sample holders Adjustment of the appropriate sample height inside of the liquid cell is the most important part of the liquid cell studies. Preparation of the sample holder may take much time however do not forget that if you hesitate to waste time at this step your all enforcements at the following steps will take more times. Thus stick your sample on the liquid cell sample holder, approach the surface. If you observe anything wrong, retract head and place out the liquid cell sample holder from over the liquid cell

63 62 scanner. If you observe that sample height is not enough for tip engagement with the surface, supply more adhesive tape under sample OR if the sample height is high that tip engages with the surface before o-ring is pressed by the approaching head, decrease the sample height or you need to change the liquid cell sample holder. Sample preparation methods vary according to the sample. Please searched related literature about your sample before studying with liquid cell LASER ALIGNMENT In the case of liquid cell studies laser alignment is not different from laser alignment with standard cantilever holder. After loading to appropriate cantilever onto the groove with the help of tweezers then place it to the AFM head Check cantilever on video scene after placing cantilever holder on the head. Every part of the system (scanner, sample holder, cantilever holder etc.) must be palced parallel to each other for proper operation

64 63 Figure 2-57: Liquid cell set-up After setting up the system as in the photo above, you should align the laser and the photodedector as the same with standard sample holder. You may check the reflected laser beam with a piece of paper O-ring will be fixed between LC cantilever holder and sample holder to prevent leakage. To have correct sealing be sure about o-ring is penetrated into the groove of the cantilever holder. 2. While approaching o-ring must never be pressed firmly into its groove. Otherwise approaching may result in piezo tube scanner break

65 64 If correct sample holder is not selected according to sample height, it is possible to observe two unexpected situation. 1- Cantilever may be engaged with sample surface even if there is some place between cantilever holder and o-ring. You can also observe red light between sample holder and the head. This will most probably cause spillage of liquid from inside of the cell to the scanner after liquid flow into the cell. Solution 1: Change liquid cell sample holder with appropriate one. (If you used 3rd one at first, you should select 2nd or 1st one. If you used 2nd one, you should select, 1st one.) Solution 2: If changing cantilever holder does not work, decrease sample thickness. 2- Sample (or substrate) height would be lower. In this case tip will never engage with the surface and o-ring will be pressed more than it can bear. So approaching will be prevented by opposite force applied by o-ring. If you observe such kind of situation approaching will become useless. Then stop approaching procedure. Insisted on approaching in may cause damage on scanner. Solution 1: Change liquid cell sample holder with appropriate one. (If you used 1st one, you should select 2nd or 3rd one. If you used 2nd one, you should select 3rd one.) Solution 2: Increase sample (or substrate) thickness. You can change substrate of cantilever OR you can add more adhesive tape under substrate. After tip engages with the surface, the height between cantilever holder and sample holder should be approximately 1 mm LOADING LIQUID AND LASER REALIGNMENT First Method: If the sample is bear to be exposed with air and it can prevent its shape until flood then you can choose this method. Fill a syringe with the liquid and get rid of from all air bubbles inside of it. Air bubbles can become trapped inside of the cell and disrupt laser alignment, resonance frequency and so image quality. Liquid flow should be very slow while passing into the cell. Be always patient during injection. (If the liquid cell is connected to the peristaltic pump, liquid flow rate should be mL/min.)

66 65 After tip is close to surface inject liquid via inlet tube. The outlet tube should be connected to a container where liquid can drain. Then connect another syringe to the outlet tube to stable the inside of the liquid cell chamber. Inside of the liquid cell should be filled with liquid completely. Be sure that there is not any leakage from any connection or near of the o-ring. If any spillage occurs turn off the power and dry wet parts. Check cantilever position in camera scene, after flood cantilever position will be changed in camera scene. If you could not observe any displacement of cantilever position in the camera scene, this means that there is most probably an air trapped over cantilever. At this situation retract the head, drain the liquid outside and start at the beginning. Laser beam s optical path which is coming from laser diode and going through the photodedector also changes because of air-liquid and liquid-air interface. Second Method: If the sample is vulnarable of air conditions or a selective solution is necessary, then you can choose to prepare liquid cell with this method. Prepare your sample on the liquid cell sample holder. Flood the liquid inside of the cell with any kind of pippette. Then place the liquid cell sample holder onto the scanner.

67 66 Figure 2-58: Liquid drop on the sample Sample surface must be covered with liquid and inner of the sample holder should be filled completely. Load cantilever on cantilever holder. Drop some amount of liquid on the backside of the glass untill it is covered by liquid. Place cantilever holder to the head. Operating with this method, cantilever is seen blur at the first time. Once you align the laser, realignment before scanning is not necessary. However, observe cantilever situation on dsiplay and red spot on photodiode window while approaching. If there is any change occurs, place off the cantilever holder and load liquid on the back of the cantilever and place cantilever holder to the head. Align laser and photodedector stages, then start approaching. If the head is very far from the surface, you can select coarse and fast approach. However, decrease step size coarse medium

68 67 when the tip becomes closer to the LIQUID SURFACE. Use fine steps during the engagement of the tip and the liquid. Slow steps also prevents or allow a little amount of leakage through pools of sample holder. Figure 2-59: Cantilever holder approaching onto the filled sample holder If there is any liquid accumulation inside of the pools, remove liquid with syringe from the pools Then you can increase step size coarse medium untill cantilever holder and o-ring engagement. Check photodiode window and camera scene to be sure about everything is correct. For dynamic mode operation, tune cantilever. Then continue with approach untill tip engage with the surface and start scan.

69 68 Figure 2-60: Camera view when liquid is injected completely into the cell. Cantilever scene will become blurring and its position goes upside of display. Then readjust the laser and the photodedector stages. The presence of liquid may cause bounced laser spot to refract slightly. This requires little adjustment with laser stage screws to align the laser spot back onto the end of the cantilever. Doing this alignment check bounced laser spot with a piece of paper. Then adjust the photodedector with the photodedector stage adjustment screws. Figure 2-61: Photodedector stages

70 69 After flood bounced laser beam will be refracted to upside OR downside of the origin of photodedector cross and Ftotal value will decrease approximately V. Figure 2-62: Beam reflection at different media

71 70 Before imaging you should realign the laser stage and photodedector stage. Figure 2-63: Photodedector stage After fluid injection, you can observe red spot on photodiode window like above. However, you should observe F total value with little decrease from the value read before injection. F normal and F lateral values can be observed with drastic changes. If you observe f total value as approximately zero, there will probably be an air bubbles trapped near or above the tip. At this situation it is better to eliminate air bubbles with strong injection OR it is better to retract head and flood again. Occasionally, air bubbles which interfere with optical beam path of laser will become trapped near the cantilever. This may cause bad or false refraction from the cantilever as shown in Figure In this case, first try to move air bubbles from nearside of cantilever by force liquid quickly through inlet tube with syringe after to make unconnected the outlet tube syringe. If this is not work, retract head, blow off liquid from inside of the cell and start from the beginning. If sealing

72 71 is achieved and there is not anything wrong, then go on with approaching to surface and engaged tip with sample surface. Figure 2-64: Wrong photodedector stages If it seems there is not any trouble about air bubbles, go on with realigning the laser beam

73 CONTACT MODE OPERATION IN LIQUID CELL Once find the surface with doing all steps successfully written above, and then you can continue with standard contact mode and scanning procedures. This part is not different from standard contact mode operation. Please refer to AFM manual for contact mode operations DYNAMIC MODE OPERATION IN LIQUID CELL Dynamic mode is more reliable for soft biological samples in air. In this mode cantilever is oscillating with given drive amplitude at resonant frequency. Liquid cell studies open new era for nanobiotechnology and nanomedicine in means that you can image biological samples as alive in their native environment. On the other hand, in the case of dynamic mode imaging in liquids is more challenging than imaging in air. Dynamic mode procedures in liquid differ in tuning with those in air. Frequency sweep occurs in liquid cell studies. If you select to operate system with dynamic mode, first do all steps of dynamic mode in air (see AFM user manual). Select appropriate cantilever for liquid cell studies. Mount cantilever to the cantilever holder, align laser beam on it and tune cantilever in air. Selecting Appropriate Cantilevers: For Dynamic Mode operations in liquid, best results are usually obtained with the 125 micron, narrow-legged gold coated cantilevers (Generally, Nanosenszors PPP-NCSTAu Model shows best performance in liquids. Standard non-contact mode cantilevers (Budget Sensors Tap300 model, NanoSensors NCH Model) are also selected for usual usages. For highest resolution, triangular shaped tips can be preferred. For Contact Mode operations, to get a highest resolution, triangular shaped silicone nitride cantilevers can be chosen. (Budget Sensor s SiNi type is suggested).

74 73 Users should experience to find which cantilevers work best for their sample. Auto-tune Curves & Selective Parameters: Imaging parameters are adjusted similar to the parameters in air before starting to approach. Table 2-2: Typical parameters of the cantilever in air F total: V Read RMS: V Set RMS: V Center Freq.: Hz Figure 2-65: Resonance frequency curve with the liquid cell cantilever holder in air

75 74 After injection of liquid into the liquid cell and be sure about cell is completely full with liquid, tune cantilever once more in that position. Decrease in resonance frequency of cantilever and also decrease in Q value will be observed after tuning. Entrapped air bubbles at near of the cantilever and false refractions of bounced laser may cause to get false curves other than real one. Generally, cantilever resonance frequency in liquid is observed half of resonance frequency in air. Table 2-2: Typical parameters of the cantilever in liquid F total: Read RMS: Set RMS: Center Freq.: Figure 2-66: Resonance Frequency curve of the same cantilever in liquid Observe that read RMS value becomes nearly equal to zero. This means that cantilever is oscillating at frequency different from it is to be. In addition you observe that ftotal value decrease a little bit, ~200mV, after laser and photodedector alignment. To be able to find the true resonance frequency

76 75 in liquid, increase excitation amplitude to 100. Then press auto-tune and find frequency and phase curves. If you use cantilever whose resonance frequency is around 300 khz, set parameters in liquid for tuning should be: Start Stop Increment Hz Hz 100Hz If cantilever frequency is around 150 khz, set parameters in liquid should be: Start Stop Increment 0Hz 50000Hz 100Hz The reason for these increment limitations is precaution to avoid from false curves. For example, if you use cantilever whose resonance frequency is 300 khz in air, it s resonance frequency is around khz in liquid. If you observe peak of center frequency in another range, it is most probably wrong peak. The reasons of this are air bubbles and incomplete flood into the cell. Figure 2-67: Wrong resonance frequency peak

77 76 After tuning procedures, set 50% of read RMS value and approach the surface. The system is ready to scan when tip is engaged with sample surface. Scanning procedures are same with standards. Set desired scan area, speed and select appropriate channels and start scan. As first trials, imaging of samples such as calibration sample or any sample which are known by user are suggested. This helps you to understand how to study easily with the liquid cell CARE OF THE LIQUID CELL PARTS When sample imaging is completed, remove the liquid from the cell. Unconnect inlet syringe from tube mount and drain out liquid with the help of outlet syringe. Then carefully remove liquid cell sample holder from the scanner head and liquid cell cantilever holder from the AFM head while avoiding spills. Take off cantilever from the groove. Rinse and dry the cantilever holder, sample holder and o-ring to pre vent the buildup of salts or other contaminants on these parts. When cleaning the cantilever holder, take extra care to avoid scratching the glass surfaces in the center of the cantilever holder CHEMICAL COMPATIBILITY OF PEEK Chemical Acetone Ammonia PEEK compatibility A A Hydrochloric Acid Hydrofluoric Acid Hydrogen Peroxide Isopropyl Alcohol Nitric Acid B C A A B to C

78 77 Sodium Hydroxide Sulphiric Acid A C A: Good B: Fair C: Not Recommended Do not forget that chemical compatibility is also affected by length of exposure, temperature, pressure, concentration, etc.

79 78 3. AFM Control Electronics 3.1INTRODUCTION The SPM Control Electronics system is composed of modules with different functions and the case as shown in Figure 3-1. The electronics should be switched on/off before the software is switched on/off. The on/off switch and voltage selector is positioned at the rear left. A 20x5mm fuse protects the AC input and operating voltage can be selected by the user, 100V/110V/220V/230V. The ventilation inlets at the top, bottom and rear panels should not be blocked and nothing should be placed at the top of the instrument, which may cause excess heating. The modules and connectors wiring the microscope to the box MUST NEVER be connected/disconnected while the power is on. Please wait for a minute or so after switching the electronics off, to discharge the power supply before disconnecting any leads from the AFM or electronics box modules. Specifications are valid for an ambient temperature of less than 30 ºC and relative humidity of less than 50%. Figure 3-1: AFM Control Electronics

80 POWER SUPPLY CARD This card generates all the relevant regulated voltages for the SPM Controller (+220V, -200V, +15V, -15V, +5V, +8V, -8V & +420V). There are LEDs which show the status of any supply. The block diagram of the Power Supply card is given in Figure 3-2. If one of these LEDs is gone during the operation, it means that the fuse may have blown. If so, please switch the power off, wait for 3minutes, until all the capacitors are discharged, pull the card out, remove the top cover. Inspect the fuses and replace the burnt one. Replace the fuse with an appropriate spare fuse and put the cover back. The fuse values are given at the Table 3-1. If the problem persists the may be one of the regulators blown. Sometimes, even though the LED is not lit, the voltages can still be generated, please check the voltages from the backplane. The ±8V is generated from ±15V supply and are intended for reducing power dissipation of i-v converters in some applications. 9-pin D-type connector supplies ±8V & ±15V for head amplifiers ( i-v converter & Hall probe preamplifier ). The head amps are hidden at the head of AFM. The head amps of the AFM system houses X&Y tilt sensors as well. The i-v converter s gain is 100mV/nA.

81 V V V + HV - 15 V + 15 V - 8 V + 8 V PS OUT Power Supply Figure 3-2: Block Diagram of Power Supply Card Voltage +5V +15V -15V +220V -200V +420V Fuse Number Fuse Type 1.5 A 1.5 A 1.5 A 50 ma 50 ma 50 ma (20x5 mm) Medium Medium Medium Medium Medium Fast Pin # at backplane Table 3-1: Fuse values for the PS Card

82 81 The problem with the power supply subunits can be from other modules as well. To make sure, unplug all the modules and switch the SPM Controller again. If all the LEDs are fine, then the problem would be with one of the modules. Switch the power off and wait until all the LEDs are off, then put one of the modules, switch the SPM Controller Power and see the LEDs at the front panel. Repeat this one by one to identify the problematic module. In some cases PS unit seems fine with no loads from the modules, but the voltage drops as some current is drawn from the power supply. You can use a DMM to check the voltages from the Backpanel. The front panel D-9 connector voltages are tabulated in Table 3-2. Pin No Output + 8 V GND - 8 V + 5 V GND + 15 V NC* NC* - 15 V * NC : Not Connected Table 3-2: Output of PS Card at the front panel

83 TEST/CALIBRATION PROCEDURE 1. After installing the PS, turn the power on and observe 8 LEDs. Make sure the all of them are lit. 2. Now turn the power off and install an extension board but wait for a few minute the PS Card LEDs to turn of. (Since there are no other Card(s) installed to the system the capacitors of the PS Card will discharge in a long time.) 3. Now check the PINs 1(top most pin), 19, 20, 21, 22 and 32 of the extension board and make sure that there are about -15V, 430V, +220V, -200V, +5V and +15V respectively. 3.2 SCAN DAC CARD This card generates the scan voltages V X and V Y used for scanning the piezo tube. The output range and the resolution are ±10V and 18/20bits, respectively. These voltages are sent to HV amps card through the backplane. You can check the function of this card by changing the X & Y scan offsets and inspecting the NSEW outputs of the HV amps. The block diagram is given in Figure 3-3. Scan DACS Figure 3-3: Block Diagram of Power Supply Card

84 TEST & CALIBRATION PROCEDURE 1. First make sure that PS Card and Micro A\D Card are installed to the system. Now install the Scan DAC Card to the extension board. 2. Check pot1 and pot2. Adjust pot1 such that it is equal to 16*R11 - R12. Similarly adjust pot2 such that it is equal to 16*R13 R14 (The values are typically 10K). 3. Connect one of the probes of a scope to the Y-Scan TP (left part) and connect the other one to the X-Scan TP (right part). 4. Open the software an turn the power on. 5. Set both the X offset and Y offset from 0µm to 21µm. You should see a change in both channels as in the Figure 3-4. Figure 3-4: The signal at both X&Y offset

85 84 6. From the menu bar select Command>Scan Multiple Images. In the Scan Image window check the box It in the Channels/Gain box. In the Scan Area box enter 56 for the X and Y Scan Area values. Enter junk in the Directory as the name of the folder for files to be saved. Enter the Number of Scans (typically 10 times) and select Scan Type as RealTime SHPM Scan. 7. Now click Start Scan button. The wave on the scope must be like this: Figure 3-5: The signal in Scan Mode Channel-1: X offset Channel-2: Y offset Figure 3-6: The signal of X offset in Scan Mode

86 85 Figure 3-7: The signal of Y offset in Scan Mode 8. Turn the power off and uninstall the card. Make sure you wait long enough that all of the PS Card LEDs are off before removing the card. 3.3 HV AMP This card combines and amplifies X & Y scan voltages (from Scan DAC card) with Z-voltage (from control card) and generates N,S,E & W voltages to drive the scan PZT. This card supplies the piezo drive signals for the quadrant electrodes of the tube piezo as follows:

87 86 S ( South ) = 10 * ( V Z + V Y ) N ( North ) = 10 * ( V Z V Y ) E ( East ) = 10 * ( V Z V X ) W ( West ) = 10 * ( V Z + V X ) where V X, V Y and V Z can take values ±10V. Therefore the outputs of the HV Amp card should be able to swing ±200V. You can check the amplifiers by changing the X & Y scan offsets and lifting off the scan head by 18.5V and releasing the lift-off. If any off the NSEW amplifier cannot swing ±200V, then it is burnt and needs to be replaced. The outputs of these amps are not short circuit protected! South North West East HV Amps Figure 3-8: Block Diagram of High Voltage Amplifier Card

88 TEST & CALIBRATION PROCEDURE 1. First make sure that PS Card, Micro A\D Card, Scan DAC Card, DAC Card and Controller Card are installed to the system. Now install the HV Amp Card to the extension board. 2. Turn the power on and open the software. 3. Set both the X offset and the Y offset to 0. From the menu bar select Commands>Automatic Approach (Make sure the head was released.). With a scope observe the 4 outputs (South, North, West and East) of the HV Card. You should see a sawtooth shaped wave with a ±200V peaks from all outputs.

89 88 Figure 3-9: The signal in Automatic Approach Mode at the channels of HV Amp. 4. Now set X offset from 0 to +21µm and observe the West and East outputs of the HV Card. You should see again a triangular waveform while North and South outputs are constant. The waveform of the East output must be an increasing shape while West is decreasing one.

90 89 Figure 3-10: East(Ch-2) and West(Ch-1) channel signal in Offset mode 5. Do the same thing for Y axis and observe the South and North outputs. Now the other outputs must be constant waveforms. The waveform of the North output must be an increasing shape while South is decreasing.

91 90 Figure 3-11: North(Ch-2) and South(Ch-1) channel signal in Offset mode 6. Set X offset from +21 to 0µm and do the same thing in step 4. You should see again a triangular waveform while North and South outputs are constant. But now the waveform of the East output must be a decreasing shape while West is increasing one. Figure 3-12: East(Ch-2) and West(Ch-1) channel signal in Offset mode

92 91 7. Do the same thing for Y axis and observe the South and North outputs. Now the other outputs must be constant waveforms. The waveform of the South output must be an increasing shape while North is decreasing. Figure 3-13: North(Ch-2) and South(Ch-1) channel signal in Offset mode 8. Now go to the menu bar, select Commands>Scan Images. Do the same thing explained in the Steps 5, 6 and 7 of Scan DAC Card part. But now set the scan type as Fast SHPM Scan with a Scan Speed of 100µm/sec. You must observe triangular waveforms which are constantly changing only in the West and East outputs which are symmetric with respect to each other.

93 92 Figure 3-14: West and East signal in Scan Image Mode 9. Turn the power off and uninstall the card. Make sure you wait long enough that all of the PS Card LEDs are off before removing the card. 3.4 DAC CARD This card has four 16bit DACs which supplies V Bias, Z offset, V coil & I SET for the SPM Controller as shown in Fig Output range of these voltages can be selected by jumpers on the card, ±10V ( default ), ±5V, ±3.3V and ±2.5V. You can check the voltages generated by the card from the BNC connectors at front panel using an Oscilloscope. V Bias is for sample bias. V Bias is low pass filtered and supplied at the BNC. The bias voltage value is also read by the SPM Program regularly and displayed as shown in Fig to warn the user. Check the whole range of ±10V can be generated by the system. If V Bias shows 0V or some value different than what you set, then there can be a short circuit or finite

94 93 Coil Zoff Iset Vbias Dac card Figure 3-15: Block Diagram of Digital to Analog Converter (DAC) Card resistance between the sample and the ground or sample and the Hall probe through its bonding wires. Z off is for lifting off the scan head. Set the lift off value at the SHPM Toolbar to 18.5V. You can use the SPM Program, SHPM > Lift Head menu to increase the Z off as shown in Figure 3-16.

95 94 Figure 3-16: Lifting off the scan head: Menu details and signal output TEST & CALIBRATION PROCEDURE 1. First make sure that PS Card, Micro A\D Card and Controller Card are installed to the system.. Now install the DAC Card to the extension board. 2. V bias : a. Connect a multimeter through a BNC cable to the fourth BNC output from the top of the DAC Card. b. Open the software and make sure you turned on the supply of the system. c. Set the V bias value from the software to 0V.If the value you read from the multimeter is 0V then adjust pot2 on the PCB such that the V bias is 0V. Also check the value read from the software agrees with the multimeter. d. Check also for various V bias vaules between ±10V as you did for 0V. (It is suggested that you check voltage values from -10V to +10V by 1V increments.) 3. V Z offset : a. Connect the BNC cable of a scope to the second output from the top of the DAC Card.

96 95 b. From the Head Liftoff box, check if the Head was lifted or released. Accordingly from the menu bar select SHPM>Release Head or SHPM>Lift Head. You must observe a decreasing or an increasing shape respectively according to the command you select. Note that there will be a 1.2V difference between the voltage you set and the observed voltage in the liftoff box and the difference is 0.29μm. Figure 3-18: Vz signal in Release Head and Lift Head options 3.5 MICROCONTROLLER & A/D CARD This card facilitates the computer interface using RS-232 serial port and PCI I/O Card. It measures the relevant 8-channels of voltages with 16 bit resolution at a maximum speed of 200k samples/s. The serial port can be used alone to control the electronics. The PCI I/O can also be used alone. The channel gain can be selected from 1,2,4 & 8. You can check the reading of the card by applying an input voltage to the I T in BNC connector of Control card and comparing with the read value by the program. For this input, 100mV translates into 1nA.

97 96 Serial Parallel Micro A/D Figure 3-19: Block Diagram of the Microcontroller A/D Card TEST & CALIBRATION PROCEDURE 1. First make sure that PS Card and DAC Card are installed to the system. Now install the Micro A/D Card to the extension board. 2. Connect a parallel cable to the PC and to the card. 3. Now open the software and turn the power on. When program opens check the boxes at the status bar which is at right bottom of the window. If you see Digital I/O Channel then the parallel channel works good. 4. If serial cable is plugged in you will see Serial Channel in the status bar next to the Digital I/O Channel.

98 97 5. If you cannot see them, you ll need to check the cable connections. 6. Close SPM and open SPM DEBUG. From the menu bar select DEBUG>Test Micro A/D. Click Start button. Now with a scope observe the IC14 data pins (6 to 22 excluding 14 which is the GND pin). If you can see data in the data pins then it works well. 7. Turn the power off and uninstall the card. Make sure you wait long enough that all of the PS Card LEDs are off before removing the card. 3.6 CONTROLLER CARD In LT-STM Mode, the Controller Card achieves tunnelling feedback and keeps tunnel current constant by adjusting the tip-sample separation. There is a 100mV/nA gain current to voltage converter at the Head Amp box attached to the head. Output of this i v converter should be connected to I T in of the card. I t out is the buffered version of I T to monitor the operation of the microscope. Remember that 100mV corresponds to 1nA current flowing from sample to tip. In LT-AFM Mode, the External input (Ext in) is used for reading any voltage value into the card and for AFM feedback. In LT-STM mode, tunnel current input is first rectified, then passed through a logarithmic converter( to linearise the exponential I T distance relation ), then compared with a set current value. The output of this comparator is amplified and integrated to give the voltage output to be sent to the HV amplifier. V Z output at the front panel is buffered output of the control card. The set tunnel current and gain of the loop can be set by software. +10V at the V Z means the scan PZT is fully extended, 10V at the V Z means the scan PZT is fully retracted. There is a x10 gain at the HV amp card, so the full range is ±100V

99 98 for the Z-motion. X&Y scan signals are added electronically, they give another ±100V. Therefore resultant voltages applied to the Scanner Piezo Electrodes are ±200V. It in It out Ext in Vz Controller Figure 3-20: Block Diagram of the Controller Card In LT-AFM Mode, the logarithmic amplifier is discarded. The feedback loop gain [1-999] changes the gain of the amplifier and affects the response speed of the microscope to changes in tunnel current or force. Higher the gain, faster the microscope responds to the changes. To inspect the card is functioning properly do the following tests in LT-STM mode, when the microscope is not in tunnelling: 1) Set the feedback gain to 999, V Bias =1.0V and I SET = 2nA in the software. Disconnect the cable of I T in of control card. 2) Connect a coaxial cable between V Bias and I T in of control card. The V Z out signal should go from +10V to 10V in ~14s. 3) Disconnect the coaxial cable between V Bias and I T in of control card. The V Z out signal should go from 10V to +10V in ~8s. 4) If it is not doing this, there can be a problem in the card. Set the feedback gain to 0 and then 999 again and repeat the step [1-3].

100 99 1. First make sure that PS Card, Micro A\D Card, Scan DAC Card and DAC Card are installed to the system. Now install the Controller Card to the extension board. 2. Check the trim pot values such that pot3 is 5K, pot4 is 23.5K, pot5 is 1.18K and pot6 is 500K. 3. Connect It out to a scope and It in to a signal generator. Set the signal generator to a sine wave with amplitude of 3V peak-to-peak and frequency of 10Hz. Look at the voltage across the R10 and make sure that there is a voltage drop of 2.5V on it. Now look the TP1 on the PCB. The waveform of this point is the rectified signal of It out. Figure 3-21: The signals of It out (Ch-2) and TP1 (Ch-1) 4. Make sure that you connect It out as X probe of the scope. Now connect TP2 as Y probe and select XY mode from the scope. Note that TP2 is the logarithm of It out. You should see a figure as below.

101 100 Figure 3-22: The signals of It out (Ch-2) and TP1 (Ch-1) Figure 3-23: The signals of It out (Ch-2) and TP1 (Ch-1) in XY mode

102 101 As can be seen from the figures the 0 crossings are at 600mV on the X axis. When the amplitude is set to 6V from the signal generator there is a gain drop of -1V/dec. Figure 3-24: The signals of It out (Ch-2) and TP1 (Ch-1) in XY mode 5. Now connect the scope to TP3. It is the same as TP2 signal with a level shift. You can adjust the level shift by setting the Tunnel Current. 6. Connect TP4 to the scope and change the Loop Gain. See the amplitude change of the same shape in the TP2. Now connect It in and Ext in together to the signal generator through a T BNC and BNC cables. From the menu bar select nc-afm>ext. Mode Options. Select XY mode. Change delta F by ±5Hz and see the ±5V shift with respect to It out. Note that when you set +5 Hz the shıft will be -5V and vice versa. Also check the change when you change the gain value.

103 102 Figure 3-25: The signals of TP4&TP2 Figure 3-26: The signals of TP4&TP2 7. Now connect TP5 to the scope. Select LT-SHPM from the Edit>Options>Admin Settings. Connect It in to V bias. Observe the V z on the scope. Set V bias to 0V and Tunnel Current to 1nA. From the menu bar select

104 103 Commands>Automatic Approach. You will see a figure as shown below. Also check for the voltage values of V bias between 0-1. V z and TP5 signals are symmetric with respect to each other. TP6 signal has also the same shape as V z. Figure 3-27: The signal of V z and TP5 8. From the menu bar select Test>Hall Probe>0. Check the DAC pin 25 which is the negative of TP4 signal. 9. Connect the V bias to It in and V z to the scope through BNC cables. Set Tunnel Current to 0.5nA. From the menu bar select Commands>Automatic Approach.

105 Adjust pot1 and pot2 together such that the fall time of the waveform is 13.5s and the rise time of the waveform is 1.4s. Run the system for about 1 hour and adjust the pots again because due to high temperature the period can change. (a)

106 105 (b) Figure 3-28: The signal of V z (a)the decreasing time(b)the increasing time Turn the power off and uninstall the card. Make sure you wait long enough that all of the PS Card LEDs are off before removing the card. 3.7 PHASE LOCKED LOOP(PLL) CARD In LT-AFM Mode, Phase Locked Loop(PLL) Card sets the Quartz Crystal Tuning Fork Force sensor into oscillation and measures the changes in its resonance frequency ( Δf ) and amplitude (A). The range of operation is between khz with 4 measurement range: ±150Hz, ±300Hz, ±450Hz and ±600Hz. The sensitivity and lock range of PLL Card is tabulated in Table 3-3. The firmware of the PLL Card can be field upgraded using the SPM Control Software. The PLL card generates the excitation signal applied to dither piezo. Dither piezo shakes the quartz force sensor generating a voltage at the same frequency. This signal is amplified by the Head Amplifier and fed into f in input of the card. The PLL Card adjusts the phase of the oscillator to set the system into resonance and the digital Phase Locked Loop measures the frequency shifts. When the AFM tip gets close to specimen surface, the resonance frequency shifts. This shift, Δf,is measured by the PLL card. The centre frequency, lock range of the PLL, amplitude and and the phase of the oscillator can be adjusted by the SPM Control Software. The software can find the resonance frequency, quality factor and locks the Quartz Crystal tuning fork at automatically. The PLL Card can also be used with an externally oscillated AFM Systems, just measuring the frequency shifts,δf or Dual Channel Lock-in Mode, where amplitude and phase of input signal is measured.

107 106 Figure 3-29: Block Diagram of Phase Locked Loop(PLL) Card Lock Range ±150Hz ±300Hz, ±450Hz ±600Hz Sensitivity 15 Hz / V 30 Hz / V 45 Hz / V 60 Hz / V Table 3-3: Sensitivity and Lock Range of Phase Locked Loop(PLL) Card TEST & CALIBRATION PROCEDURE TAPPING MODE Connect the RMS out, ΔF, AFM out, Ext. in outputs to the oscilloscope with T BNCs Approximately the same RMS values should be read on RMS, AFM out and Ext. in channels.

108 107 Channel 1: RMS out Channel 2: ΔF Channel 1: AFM out Channel 2: Ext. in The ΔF signals should be changed between +150 ;-150 Hz while Auto-Tuning

109 108 Channel 1: ΔF Channel 2: RMS out The ΔF signals should be changed in 360 while finding phase Channel 1: ΔF Channel 2: RMS out

110 109 Channel 1: AFM out Channel 2: Ext. in NONCONTACT MODE Connect the RMS out, ΔF, AFM out, Ext. in outputs to the oscilloscope with T BNCs. The amplitude value should be seen on RMS channel.

111 110 Channel 1: ΔF Channel 2: RMS out ΔF, AFM out and Ext. in signals should be changed between +150 ;-150 Hz while Auto-Tuning Channel 1: ΔF Channel 2: RMS out

112 111 Channel 1: Ext. in Channel 2: AFM out The signals except from RMS out should be changed in 360 while finding phase

113 112 Channel 1: Ext. in Channel 2: AFM out Channel 1: RMS out Channel 2: ΔF 3.8 SPARE A/D CARD Spare A/D Card lets the SPM Controller to digitise up to 8-channels of more input signals with 16 bit resolution at a maximum speed of 200k samples/s. The channel gain can be selected from 1,2,4 & 8. The inputs are differentially buffered. If the module is mounted in single slot, there are only 4 channels activated.

114 113 Figure 3-30: Block Diagram of the Spare A/D Card TEST & CALIBRATION PROCEDURE 1. First make sure that PS Card, Micro A\D Card and are installed to the system. Now install the Spare ADC Card to the extension board. 2. Turn the power off and uninstall the card. Make sure you wait long enough that all of the PS Card LEDs are off before removing the card. 3.9 PCI BUS DIGITAL I/O CARD This card, which is mounted on the PC, facilitates high speed data acquisition. The board has no switches or jumpers to set. To install your hardware: 1. Turn the computer OFF, open it up, and insert the board into any available PCI slot.

115 Close up the computer and turn it ON. 3. Some operating systems, such as Windows 9x or 2000/XP, automatically detects the board as it starts up. The simplest way to configure and test your installation is to use the InstaCalTM program provided. InstaCal is the installation, calibration, and test software that is supplied with the Digital I/O board on the computer. InstaCal shows you any available options, and creates a configuration file that your application software refers to. The software you use automatically has access to the exact configuration of the board. The configuration can be done by switching the SPM Controller off and closing the SPM Control Program first. Then the Instacal program should be run from Programs-> Measurement Computing -> Instacal from the Windows Menu as shown on the figure a. The properties (configuration) of the board may be changed by double-clicking on the board name. For plug-and-play boards, many of the properties are set by the system and cannot be changed through InstaCal. After running the software installation program, installing your board in the PC, and setting your board configuration with InstaCal, test the installation. Select the Test menu and then select the board you want to verify. Select the type of test to perform (Digital for the card on this system) and follow the instructions provided. If you have failure at the end of the test, Check your connections and installation procedure. Please note that the SPM electronics harware should be off during Digital I/O card test and configuration.

116 115. (a) (b) Figure 3-31: Instacal Program (a): Program interface (b): Card testing interface

117 Installing and Running SPM Program 1) Open Error! Hyperlink reference not valid. page

118 117 2) Save Last version of the software 3) Run it

119 4) Click edit > options 118

120 - LASER AFM MODE SHOULD BE SELECTED AS SPM TYPE 119

121 Adjustment of Cantilever, Focus and Photodedector 1. Select an appropriate cantilever (Cantilevers should be selected depending on selected mode) and place it at the cantilever holder as you press the pin to release the cantilever holder spring. 2. Place the cantilever holder on the groove. 3. Observe the cantilever is seen on the integrated video microscope scene. 4. Turn Laser OFF on Photo Diode Adjust Bar

122 Enter min and max values of Laser Intensity on Laser State bar Min =0 (enter) Max =100(enter)

123 Adjust Laser Intensity 0 7. Turn the laser ON on Laser State and adjust laser intensity NOTE: F total value can be ~ 1.00 V 8. Turn the laser on and adjust the laser power to 20%. 9. Place a piece of white paper under the AFM head so that you can see the projection of the cantilever with the laser light.

124 To be able to drop the laser spot on the tip adjust the X and Y screws. ( At this point you should see the reflection of the laser spot from the cantilever end at the video camera and the shade of the cantilever at the paper below.) 11. The X screw will move the laser spot along the X axis and the Y screw will move the laser spot along the Y axis. Y X

125 Click the photo diode adjust dialog at the SPM Control Software s main window. 13. By playing with the photo detector screws roughly position the photo detector at the center of the laser beam bounced from the cantilever. 14. Look at the computer screen and try to bring the dot at the centre of the crossed hairline by playing with the screws Y&Z. As you do this, the F TOTAL should not change or decrease too much. 15. The Y screw will move the photo detector along the Y axis and the Z screw will move the photo detector along the Z axis. Z Y

126 125 Z Y 16. After completing the laser & photodetector adjustment the AFM is ready to run in the desired mode of operation. 6. Approaching the Surface 1. Click Commands> Approach 2. Motor Control window will be open.

127 126 Z ICONS WILL DRIVE MOTORIZED Z STAGE. X & Y ICONS WILL DRIVE MOTORIZED XY STAGE. 3. Please check Motor Options. Fine steps should be the same as written in the boxes below. Coarse steps should be the same as written in the boxes below.

128 127 NOTE: Those values can be differed according to encoder of the motor stages. So you can increase or decrease the step sizes. 4. Choose coarse and fast if you far from the surface then approach 5. When you get closer to the surface choose medium step( you can control how far you are from the surface by using cameras)

129 When you see the cantilever and its reflection on side view camera choose slow steps 7. If cantilever is so closer to the sample choose fine and slow or choose Commands>Automatic approach

130 129 Auto-approach will drive motorized Z stage with Fine Slow step size. NOTE: Check the feedback value at each step. It mustn t be ~0,0. If it is that means you crashed the surface.

131 It is better if the Vz is around ~0 2 V. 7. Scanning the Surface 1. Select Command>Scan Multiple Images 2. Click Channels

132 Select Normal AFM Scan from the Scan Type. 4. Select Channels for Contact Mode ; 10xFN, Vz, FN, F_Lateral FFM Mode ; 10xFN, Vz, FN, F_Lateral

133 132 Dynamic ; RMS, Vz, Phase Non-Contact ; RMS, Vz, Delta_F

134 133 STM ; It, Vz MFM ; MFM RMS, Vz, MFM Phase

135 134 EFM ; EFM RMS, Vz, EFM Phase 5. Select Scan Options. Enter scan area, scan speed and Image Size

136 135 NOTE 1 : The images are automatically saved in image folder of program. You can set specified name and directory for images. NOTE 2: To scan the max.area, the scan offsets must be (-20) µm x (-20)µm. NOTE 3: To change XY and Z scales,click Edit>Options>General.

137 136 8)To beginning to scan, click on Start Scan Icon. NOTE : The Scan lines acquired by the microscope are displayed one by one, to form the images. Forward and backward scan are acquired and displayed for every chosen image channel. If you want to start a new image or take the microscope out, first pull the sample back by 40~50 fineslow steps.

138 Never switch the electronics off before retracting the cantilever and closing the SPM Software Contact Mode Applications 1. Select Contact mode on Laser AFM Bar. 2. Put the cantilever to cantilever holder and focus the laser spot on it and adjust the photodetector (see Appendix 2).

139 Enter Loop Gain min and max values Min =0 Max = Adjust Loop Gain Set minus value of F-Total as the Normal Force set value. NOTE: F total value can be ~ 1.00 V 6. To approaching the surface click on Command>Approach 7. Approach the surface safely (see Appendix 3)

140 139 NOTE : Check the Normal Force Value at each step. If the AFM Head is far from the surface approach by Coarse, fast and medium step. When the Head is close to the surface, select Coarse fine and control distance between tip and surface from the top view camera. When the Normal Force is close by setting value select fine slow step and control distance between tip and surface from the side view camera. When the tip finds the surface Normal Force equlize to the set value and Vz gets below to a certain set value ~2 V 8. Command>Scan Images (see Appendix 4) 9. From Channels select FNX10,Vz,FN,F_Lateral,Ftotal 10. Select Scan Options. Enter scan area, scan speed and select Image Size

141 Click Start Scan. 9. FFM Mode Applications 1. Select FFM mode on Laser AFM Bar

142 Put the cantilever to cantilever holder and focus the laser spot on it and adjust the photodetector (see Appendix 2). 3. Enter Loop Gain min and max values Min =0 Max =999

143 Adjust Loop Gain Set minus value of F-Total as the Normal Force set value. NOTE: F total value can be ~ 1.00 V 6. To approaching the surface click on Command>Approach 7. Approach the surface safely (see Appendix 3) NOTE : Check the Normal Force Value at each step. If the AFM Head is far from the surface approach by Coarse, fast and medium step. When the Head is close to the surface, select Coarse fine and control distance between tip and surface from the top view camera. When the Normal Force is close by setting value select fine slow step and control distance between tip and surface from the side view camera. When the tip finds the surface Normal Force equlize to the set value and Vz gets below to a certain set value ~2 V 8. Command>Scan Images (see Appendix 4)

144 From Channels select FNX10,Vz,FN,F_Lateral,Ftotal 10. Select Scan Options. Enter scan area, scan speed and select Image Size 11. Click Start Scan.

145 Dynamic Mode Applications 1. Select Dynamic Mode on Laser AFM Bar 2. Put the cantilever to cantilever holder and focus the laser spot on it and adjust the photodetector (see Appendix 2). 3. Enter Loop Gain min and max values

146 145 Min =0 Max = Adjust Loop Gain Open PLL Bar by click on PLL bar button 6. Enter the minimum and maximum values to excitation amplitude on PLL bar Minimum value: 0 (enter)

147 146 Maximum value: 100 (enter) 7. Then write 5 into the excitation amp. box 8.Click on Auto Tune button 9. Auto-tune window is open 10. Enter the range points to start/stop to find cantilever s center frequency Start: 0 Hz Stop: Hz Increment: 1000 Hz

148 Click the and start 12. Click Centre/Span Insert ~2000 Hz to span and ~10 Hz to increment then click start 13. To find the phase curve click start button on the top right side of the window.

149 Check the set values then click start Start: 0 Stop: 360 Increment: After the optimum phase value is found for the PLL click finish

150 Set the ~50% value of amplitude on general bar 17. Position the sample on the sample holder 18. Approach the surface safely (see Appendix 3)

151 150 NOTE : Check the Osc. Amplitude at each step. If the AFM Head is far from the surface approach by Coarse, fast and medium step. When the Head is close to the surface, select Coarse fine and control distance between tip and surface from the top view camera. When the Osc. Amplitude is close by setting value select fine slow step and control distance between tip and surface from the side view camera. When the tip finds the surface Osc. Amplitude equlize to the set value and Vz gets below to a certain set value ~2 V 19. Command>Scan Images (see Appendix 4)

152 Select Scan Options. Enter scan area, scan speed and select Image Size 11. Click Start Scan.

153 Non-Contact Mode Applications 1. Select non-contact mode from laser AFM bar 2. Put the cantilever to cantilever holder and focus the laser spot on it and adjust the photodetector (see Appendix 2). 3. Enter Loop Gain min and max values Min =0

154 153 Max = Adjust Loop Gain Open PLL Bar by click on PLL bar button 6. Enter the minimum and maximum values to excitation amplitude on PLL bar Minimum value: 0 (enter) Maximum value: 100 (enter)

155 Then write 5 into the excitation amp. Box 8.Click on Auto Tune button 9. Auto-tune window is open 10. Enter the range points to start/stop to find cantilever s center frequency Start: 0 Hz Stop: Hz Increment: 1000 Hz

156 Click the and start 12. Click Centre/Span Insert ~2000 Hz to span and ~10 Hz to increment then click start 13. To find the phase curve click start button on the top right side of the window.

157 Check the set values then click start Start: 0 Stop: 360 Increment: After the optimum phase value is found for the PLL click finish

158 After auto-tune, delta F must be around 0,0 Hz. Set the delta F as a 10000Hz on general bar. 17. Position the sample on the sample holder 18. Approach the surface safely (see Appendix 3) NOTE : Check the ΔF at each step.

159 158 If the AFM Head is far from the surface approach by Coarse, fast and medium step. When the Head is close to the surface, select Coarse fine and control distance between tip and surface from the top view camera. When the ΔF is close by setting value select fine slow step and control distance between tip and surface from the side view camera. When the tip finds the surface ΔF equlize to the set value and Vz gets below to a certain set value ~2 V NOTE : Check the normal and total force at each step on Laser Bar. If total force around ~0,0 V and normal force upper than 0,100 V it means you can t find the surface. In this situation retract the head by coarse slow, auto-tune again and increase the delta F value. Do the same steps until you find the surface When you find the surface, delta F and setting delta F value will be same It is better if the Vz is around 0.0 V

160 Command>Scan Images (see Appendix 4) select delta F, Vz and Phase 20. Select Scan Options. Enter scan area, scan speed and select Image Size

161 Click Start Scan. 12. MFM Mode Applications 1. Select MFM Mode on Laser AFM Bar 2. Put the cantilever to cantilever holder and focus the laser spot on it and adjust the photodetector (see Appendix 2).

162 Enter Loop Gain min and max values Min =0 Max = Adjust Loop Gain 999

163 Open PLL Bar by click on PLL bar button 6. Enter the minimum and maximum values to excitation amplitude on PLL bar Minimum value: 0 (enter) Maximum value: 100 (enter) 7. Then write 5 into the excitation amp. box 8.Click on Auto Tune button

164 Auto-tune window is open 10. Enter the range points to start/stop to find cantilever s center frequency Start: 0 Hz Stop: Hz Increment: 1000 Hz 11. Click the and start

165 Click Centre/Span Insert ~2000 Hz to span and ~10 Hz to increment then click start 13. To find the phase curve click start button on the top right side of the window.

166 Check the set values then click start Start: 0 Stop: 360 Increment: After the optimum phase value is found for the PLL click finish

167 Set the ~50% value of amplitude on general bar 17. Position the sample on the sample holder 18. Approach the surface safely (see Appendix 3) NOTE : Check the Osc. Amplitude at each step.

168 167 If the AFM Head is far from the surface approach by Coarse, fast and medium step. When the Head is close to the surface, select Coarse fine and control distance between tip and surface from the top view camera. When the Osc. Amplitude is close by setting value select fine slow step and control distance between tip and surface from the side view camera. When the tip finds the surface Osc. Amplitude equlize to the set value and Vz gets below to a certain set value ~2 V 19. Command>Scan Images (see Appendix 4)

169 From Channels select Vz, MFM RMS, MFM Phase 21. Choose the Normal AFM Scan from the Scan Mode box 22. Select Scan Parameters NOTE: Head lift depends on the magnetism of your sample. 23. Select Scan Options (see Appendix 4)

170 Enter scan area values, scan speed and select Image Size 25. Click Start Scan.

171 EFM Mode Applications 1. Select EFM on Laser AFM Bar 2. Put the cantilever to cantilever holder and focus the laser spot on it and adjust the photodetector (see Appendix 2).

172 Enter Loop Gain min and max values Min =0 Max = Adjust Loop Gain Open PLL Bar by click on PLL bar button 6. Enter the minimum and maximum values to excitation amplitude on PLL bar Minimum value: 0 (enter) Maximum value: 100 (enter)

173 Then write 5 into the excitation amp. Box 8.Click on Auto Tune button 9. Auto-tune window is open 10. Enter the range points to start/stop to find cantilever s center frequency Start: 0 Hz Stop: Hz

174 173 Increment: 1000 Hz 11. Click the and start 12. Click Centre/Span Insert ~2000 Hz to span and ~10 Hz to increment then click start 13. To find the phase curve click start button on the top right side of the window.

175 Check the set values then click start Start: 0 Stop: 360 Increment: After the optimum phase value is found for the PLL click finish

176 Set the ~50% value of amplitude on general bar 17. Position the sample on the sample holder. 18. Approach the surface safely (see Appendix 3)

177 176 NOTE : Check the Osc. Amplitude at each step. If the AFM Head is far from the surface approach by Coarse, fast and medium step. When the Head is close to the surface, select Coarse fine and control distance between tip and surface from the top view camera. When the Osc. Amplitude is close by setting value select fine slow step and control distance between tip and surface from the side view camera. When the tip finds the surface Osc. Amplitude equlize to the set value and Vz gets below to a certain set value ~2 V 19. Command>Scan Images (see Appendix 4)

178 From Channels select Vz, EFM RMS, EFM Phase 21. Choose the Normal AFM Scan from the Scan Mode box 22. Images are automatically saved in the specified directory. 23. Select Scan Parameters

179 Head lift depends on the electrostatic force strength of your sample. The operator should be aware of electrostatic force domains on the surface and work function of cantilever since applied forward and backward voltage will be determined according to difference of the electrostatic force beween tip and surface. You can asked AFM experts at installation Select Scan Options

180 Enter scan area values, scan speed and select Image Size 26. Click Start Scan.

181 STM Mode Applications 1. Select STM Mode from Laser Modes. 2. The Laser will be automatically turned off. 3. Enter Loop Gain min and max values Min =0 Max = Adjust Loop Gain 999

182 181 NOTE : Please adjust Loop Gain 100 when the tip is close to surface. Control Vz (±10V) and tip position (Z µm) from the software. 5. Adjust Tunnel Current 0.5 na from Tunnel Current bar 6. Adjust V-Bias from the V-Bias bar 7. Connect Vz (channel 1) and It Out (channel 2) to the osiloscope channel. 8. Adjust the sensor NOTE : Thouch near the tip with tweezers carefully to test as if Tunnel Current is conducted to tip. You must observe change from the It Out Channel while thouching. Measure voltage between Sample Holder and Head with using Multimetre, Direct Current from 2V scale. You must read V-Bias Voltage value from the multimetre. 9. Approach the surface safely.(see Appendix 3) NOTE: If the AFM Head is far from the surface approach by Coarse, fast and medium step. When the Head is get close to the surface, select coarse fine. When the Tunnel Current is close by setting value select fine slow step.vz value will decrease from the osiloscope. When the tip touches the sample surface, Tunnel Current equlize the set value. Vz is below a certain set value ~2 V. 10. Command>Scan Images (see Appendix 4) 11. Select Vz and Tunnel Current

183 Check Scan Mode. Normal Scan should be selected. 13. Open Scan Options menu.

184 Enter desired scan area, scan speed and image Size 15. Click Start Scan.

185 Lithography Nanolithography option is used for drawing images on the sample surface by application of voltage pulses to the sample, while tip is grounded. The process uses the process of electric field enhanced oxidation of the surfaces by application of voltage pulses. The pattern to be written has to be given as a black and white bitmap image. As the tip is scanned on the sample, the SPM Controller applies a voltage pulse, height & duration determined at the Nanolithography tab. The important point here is that the image size ( X & Y Pixel sizes) selected from SPM Software and the Bitmap image size must be equal to each other. The physical size of the pixels depends on the selected scan area from SPM. For example, 5000 nm 5000 nm and 256 pixels 256 pixels area are selected for lithography. The selected flag figure have lines: 2 pixels. One pixel on the flag has the physical size: 5000nm / 128 pixels = 19.5 nm/pixel The flag has lines which are 2 pixels wide. Then the lines of the flag will be nm = 39 nm. Depending on the size of the tip, the lines drawn will obviously have a certain width. Therefore the actual size of the lines written will be larger than the 39nm width. In order to perform nanolithography, change the AFM Mode as Non-Contact. The standart Nonolithography scan is as same as non-contact scan except you should select lithography image that you want to use. From the menu bar select Commands>Scan Image and open the NanoLithography tab as shown in the Figure 1.

186 185 Fig. 1. Nanolithography Tab at the Scan Image Dialogue First, select image that you want to scan, then Lithography scan check box will be enabled. Note that the image should be black and white and should be Bitmap type. Below there is a selected bmp image sample. Its image size is

187 186 Fig. 2. Selected BMP image Now choose the Scan Options tab and enter Scan Area X and Y values. Then, enter the Image Size X and Y values. Note that the Image Size should be the same as the image you selected on the NanoLithography tab. Also enter the Number of Scans and Scan Speed according to your need. Below, there is its screen shot. Fig. 3. Scan Options Before starting the nanolithography, scan the surface and observe if it is reasonably flat and suitable for nanolithography. If not, position the head to another location on your sample for nanolithography. Finally, click on the Start Scan button on the corner of the tab and start the nanolithography process. After nanolithography, scan the same area to observe the result of nanolithography process. The scan size should have greater pixel sizes if better resolution is desired. For example, the pattern in Figure 3 is used for the nanolithography, which has pixel size. The written pattern was imaged with 512 x 512 pixel size and 5000 nm 5000 nm as shown in Figure.4.

188 187 Fig.4 Lithography Result Silicone layer should be treated with HF solution to get rid of from oxide layer on the surface of silicone. Diamond and conductive AFM tip should be used

189 Liquid Cell Applications 1. Select mode from laser AFM bar 2. Put the cantilever to cantilever holder and focus the laser spot on it and adjust the photodetector (see Appendix 2). 3. Follow the procedures for selected mode. 4. Position the sample on the sample holder 5. Approach close the surface safely (see Appendix 3)

190 Fill a syringe with the liquid and get rid of from all air bubbles inside of it. 7. Connect another syringe to the outlet tube to stable the inside of the liquid cell chamber. 8. Readjust the laser and the photodedector stages. 9. If necessary tune the cantilever again. 10. Approach the surface safely. 11. Select Scan Options. Enter scan area, scan speed and select image size and click start scan. 12. After scanning is complete excrete liquid from cell. 13. Retract from surface, remove cantilever holder and sample holder. 14. Rinse and dry the cantilever holder, sample holder and o-ring.

191 17. AFM Cable Sets 190

192 191

193 192

194 193 AFM Cable Connections CONNECTIONS: Cable Set Cable Connection Card Input I Tunnel Controller Card It in Vİdeo1 Video2 DVR Card /Computer TV 1/AV in Card 2/S-Video Head Cables Power Power Supply Power Dither PLL Card Ext. Out 10xFN PLL Card Signal in connector Spare ADC Connector Input North HV AMPs Card North South HV AMPs Card South Scan Head Cables East HV AMPs Card East

195 194 West HV AMPs Card West Vbias Dac Card Vbias Micro A/D Cable connector Dio 24 Card PC Motor Cables connector Motor Card Connector Input SUBCONNECTIONS: Card Output Card Input Spare ADC AFM out Controller Ext in PLL Card RMS out Spare ADC RMS PLL Card Freq. Out Spare ADC ΔF

196 195