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Ryan’s MFP-3D Procedural Operation ‘Manualette’ Version 10 (v080501; Igor 6.04A); 8.3 Figure 8.4: Choosing a Set Point voltage in Contact Mode: Set point must be more positive than the free air deflection voltage. ▪ On the Main tab (Figure 8.1), adjust the highlighted parameters (dependent on sample): Integral gain (I): 8 to 10: allows the Integral gain to be responsive enough upon feedback servo activation. Scan rate: 1 Hz; for softer samples, choose a slower Scan Rate. Scan angle, resolution (scan points & lines) and image size is up to you. Rotating the scan angle results in counter clockwise rotation with positive rotation angle values ▪ At this point you are ready to engage for an imaging-only application (i.e., if you are not interested in knowing the cantilever spring constant to know what forces are applied at a given Set Point voltage). See Chapter 9 if you want/need to determine cantilever spring constant. 8.2: TIP ENGAGEMENT: Click ‘Engage’ in the Sum and Deflection window (Figure 8.4). Notice the Z-piezo voltage maximizing all the way red (150 V), indicating the Z- piezo is fully extended in anticipation of engagement of the feedback servo. Slowly turn the thumbwheel counter-clockwise (towards the surface; rate ~ several microns per second) until the deflection voltage value on the S&D meter equals the user defined Set Point, AND you here a chime sound (computer speaker volume must be on). The feedback servo is now activated. You will also notice the Z-piezo voltage meter goes from ‘railed’ in the red (150 V), to some lesser value. If you have the volume up on the transducer (front of controller, headphones plugged in), you can hear a frequency change as engagement occurs- it will sound like static and will change to a dampened sound when in contact. GENTLE ENGAGEMENT: Soft engages, similar to those described in Section 6.1.2B, and also can be done in Contact Mode. Choose a Set Point voltage slightly more positive than the free air deflection voltage; you can proceed by clicking the ‘Engage’ button and wheel the tip down until the feedback servo is engaged. An even more gentle engagement occurs by wheeling down 10 μm, then click ‘Engage’; if the tip doesn’t engage, click ‘Withdraw’ button, wheel down another 10 μm, and repeat. Notice that each graduation on the front thumbwheel is 1 μm. Once feedback has been activated, continue to lower the head with the front thumbwheel to ~ 70 V (i.e. no color in Z-Piezo meter). This indicates the piezo is in the middle of its Z- range (~ 7.5 μm standard head; ~ 20 μm extended head).
Ryan’s MFP-3D Procedural Operation ‘Manualette’ Version 10 (v080501; Igor 6.04A); 8.4 ▪ At this point the tip is engaged and just sitting on the surface- it does not begin rastering until you tell it to do so. You can now being imaging (see next step) or determine the Spring Constant (see Chapter 9). If the Z-piezo voltage is railed all the way blue (-10 V) upon clicking simple engagement, the piezo is fully retracted because it thinks it has crashed. This indicates a false engagement and adjustment must be made to the Set Point voltage to allow extension of the piezo. This often occurs when imaging in fluids/ high humidity, or too low a Set Point voltage (i.e. low force). Is the acoustic hood hatch still open?- Probably. Follow steps to preserve the tip’s apex while shutting the door: Use the Hamster to decrease the Set Point voltage to pop the tip off the surface. Close the hood door. Increase the Set Point voltage with the Hamster again to hard engage; Proceed scanning. 8.3: FINE TUNING IMAGING PARAMETERS: Click the ‘Do Scan’ button on the Main tab. After a brief moment, imaging will begin. Tune the parameters with Set Point force, Integral gain (I) and Scan Rate. Use the arrow clickers (to right of setvar windows) to adjust parameters, opposed to typing values in, OR- see next bullet… ▪ Alternatively, you can fine-tune the parameters using the ‘Hamster’ wheel on the front of the controller. Any parameter with a ‘radio’ button next to it (Figure 8.1) can be changed during a scan when it is activated (looks like black/ green dot in circle) with the ‘Hamster’. The Hamster gives “digital control with analog feel”. The toggle switch to the left of the Hamster allows you to toggle between radio buttons in the panel. This is a GREAT feature for tuning on the fly, and you don’t need to use the mouse. (The Hamster is also functional in the Force panel, described later in the Section 11). Height Channel A B Image quality can be monitored by image resolution and amount of noise in the line traces (located below images). The Set Point voltage and Integral gain should first be adjusted to achieve good tracking. Figure 8.5 shows an example of imaging a calibration grid, with corresponding parameters from Main tab below. Panel A) shows the initial tracking of the tip upon engagement with a Set Point voltage of 0.4V (free air was ~ -0.45V). B) Shows that with an Figure 8.5: Image parameter tuning in Contact Mode of calibration grid.
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