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afm [2025/10/07 11:50] – [Tuning the AFM to get a good image] ethanminotafm [2025/10/07 12:02] (current) – [Step-by-step walk through for AC mode imaging] ethanminot
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     * Move laser toward the tip of the cantilever - the control wheels are labeled LDX and LDY (laser deflection x and y). They are located on the back & right side of the MFP-3D tripod. Use these controls to maximize the 'Sum' signal. If the laser is badly misaligned, it can be hard to locate. If you "loss" the laser spot, ask an experienced user for help.      * Move laser toward the tip of the cantilever - the control wheels are labeled LDX and LDY (laser deflection x and y). They are located on the back & right side of the MFP-3D tripod. Use these controls to maximize the 'Sum' signal. If the laser is badly misaligned, it can be hard to locate. If you "loss" the laser spot, ask an experienced user for help. 
     * Adjust the photodetector (PD) position. The control wheel for the photodetector is located on the left side of the MFP-3D tripod and is labeled PD. Set the PD 'Deflection' meter to near zero.     * Adjust the photodetector (PD) position. The control wheel for the photodetector is located on the left side of the MFP-3D tripod and is labeled PD. Set the PD 'Deflection' meter to near zero.
-  - X Set AC Mode - In main tab of the master panel select 'AC Mode' in the 'Imaging Mode' pull down menu 
   - Tune the AFM   - Tune the AFM
     *  Open 'Tune' tab in the master panel     *  Open 'Tune' tab in the master panel
     *  Set 'Target %' to -5.0 %. This setting is a first guess at the ideal drive frequency (setting it slightly less than the resonant frequency). You may have to test different drive frequencies later if you notice "phase jumping" during imaging.      *  Set 'Target %' to -5.0 %. This setting is a first guess at the ideal drive frequency (setting it slightly less than the resonant frequency). You may have to test different drive frequencies later if you notice "phase jumping" during imaging. 
-    * Click the 'Auto Tune' button and wait for tuning to finish. Software will set drive frequency.+    * Click the 'Auto Tune' button and wait for tuning to finish. Software will set drive frequency and drive amplitude. The graph of amplitude and phase should look like the textbook curves for a driven damped harmonic oscillator. 
 +    * In the read-out window of the software, you will now see a 1-volt amplitude signal underneath the sum signal. Maximize this amplitude signal by moving the laser along the length of the AFM cantilever. When the amplitude is maximized, the sum signal will be slightly less than its max value.  
 +    * Click 'Auto Tune' one more time (or manually adjust the drive amplitude).
   - Engage the tip   - Engage the tip
     * Set the I gain to 10     * Set the I gain to 10
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 It’s hard to predict a priori whether the best images will be acquired with phase below 90, or above 90. The best imaging regime for a given day depends on tip sharpness, cantilever stiffness, the sample’s mechanical/adhesive properties, the material and coating of the tip, and the humidity in the room. These factors modify the functional form of long-range van der Waals forces, the electrostatic forces, the way the tip indents the sample, and the capillary forces related to the water meniscus. A nonlinear tip–sample force with respect of tip-sample separation leads to bistabilities, and these bistabilities cause the phase jumps which mess up the AFM image. It’s hard to predict a priori whether the best images will be acquired with phase below 90, or above 90. The best imaging regime for a given day depends on tip sharpness, cantilever stiffness, the sample’s mechanical/adhesive properties, the material and coating of the tip, and the humidity in the room. These factors modify the functional form of long-range van der Waals forces, the electrostatic forces, the way the tip indents the sample, and the capillary forces related to the water meniscus. A nonlinear tip–sample force with respect of tip-sample separation leads to bistabilities, and these bistabilities cause the phase jumps which mess up the AFM image.
  
-===== Imaging rules of thumb =====+===== Other imaging rules of thumb =====
 It is easiest to get a good image on a small scan area (~ 2 micron). A small scan also facilitates verification of tip sharpness. Starting from the default settings you can fine tune the image and then start increasing the scan size. Good settings will minimize ringing and reduce shadows while keeping the scan rate reasonably fast. It is easiest to get a good image on a small scan area (~ 2 micron). A small scan also facilitates verification of tip sharpness. Starting from the default settings you can fine tune the image and then start increasing the scan size. Good settings will minimize ringing and reduce shadows while keeping the scan rate reasonably fast.
  
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   *Set-point amplitude 0.75 V   *Set-point amplitude 0.75 V
  
-**Adjustments to these settings**  
- 
-  
  
 **Using nanotubes as a diagnostic tool** **Using nanotubes as a diagnostic tool**
afm.1759863055.txt.gz · Last modified: 2025/10/07 11:50 by ethanminot