Differences

This shows you the differences between two versions of the page.

--- afm [2025/04/22 09:32] – ethanminot
+++ afm [2025/05/01 19:33] (current) – ethanminot
@@ Line 10: / Line 10: @@
 ===== Scheduling time =====
-The AFM calendar is managed by [[https://relms.oregonstate.edu/facilities|RELMS]]. On the RELMS website, our lab is listed as "Quantum Materials Lab". RELMS is a university-wide system administered by a team of 3 OSU employees. If you have not registered with RELMS before, the RELMS team will help you sign up and associate your billing indexes with your account. You must be trained on the AFM before you can book time on the RELMS calendar.
+The AFM calendar is managed by [[https://relms.oregonstate.edu/facilities|RELMS]]. On the RELMS website, our lab is listed as "Quantum Materials Lab". RELMS is a university-wide system administered by a team of three OSU employees. If you have not registered with RELMS before, the RELMS team will help you sign up and associate your billing indexes with your account. You must be trained on the AFM before you can book time on the RELMS calendar.
 Basic rules about booking time:
   *People who have scheduled time get priority.
   *Don't block off an entire 9am-5pm workday - leave at least an hour for someone to do a quick characterization.
+Every time you use the AFM, follow these steps:
+  - Write your name and date in the physical logbook
+  - Open your RELMS booking on the computer (or your cell phone) and "start" the session.
+  - Use the AFM
+  - Open your RELMS booking on the computer (or your cell phone) and "end" the session. RELMS will then bill your index for the actual time you used the AFM.
+  - Complete your logbook entry in the physical logbook.
+If you forget to start and/or end the RELMS booking, you will get an email from RELMS asking you to enter the actual time that you used the AFM. Please follow the instructions in the email.
@@ Line 53: / Line 62: @@
 ===== Step-by-step walk through for AC mode imaging =====
+//If a tip change is needed - see the [[AFM tip change information]]//
   - Sign into the black notebook (on the table next to the AFM)
-  - Start your RELMS reservation on the RELMS website.
+  - Start your RELMS reservation on the [[https://relms.oregonstate.edu/facilities|RELMS website]].
-  - Open version 19 of the AFM software (latest stable version as of April 2025).
+  - Turn on the laser - Key switch on the AFM computer
+  - Open version 19 of the realtime AFM software (latest stable version as of April 2025).
   - Click the first option, "Template"
   - Once software loads, set AC mode in master panel
@@ Line 67: / Line 78: @@
     * Turn on the camera light - Switch on the box which sits on top of the AFM
     * Align camera on cantilever - Two knobs sticking up at the very rear of the  MFP-3D
-    * Turn on the laser - Key switch on the AFM computer
+    * Not usually needed, but you might need to focus the camera on the AFM tip - Use the the focus ring toward the rear of the MFP-3D. The ring is difficult to turn (as of April 2025).
-    * Focus camera on the tip - Use the the focus ring toward the rear of the MFP-3D
+    * 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.
-    * Move laser toward the tip of the cantilever - Use the thumbscrews on the back & right side of the MFP-3D to maximize the 'Sum' signal
+    * 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) - Use the thumbscrews on the left of the MFP-3D
-      * Set the 'Deflection' in the S&D meter to zero (tapping mode) or a sliver negative (contact mode)
   - X Set AC Mode - In main tab of the master panel select 'AC Mode' in the 'Imaging Mode' pull down menu
   - Tune the AFM
@@ Line 78: / Line 87: @@
     * Click the 'Auto Tune' button and wait for tuning to finish. Software will set drive frequency.
   - Engage the tip
-    *  Set the I gain to 10
+    * Set the I gain to 10
-    * Make the 'Set Point Voltage' about 95% of the target amplitude (1 V by default)
+    * Make the 'Set Point Voltage' about 95% of the measured amplitude signal. (The measured amplitude signal is probably 1 V right now)
     * Click 'engage' in the S&D meter and
-    * Lower the tip (tripod thumbwheel — left = up, right = down) while watching the amplitude. The amplitude will drop as you near the surface. The computer will beep when feedback kicks in to stop the amplitude from dropping below the setpoint. Continue lowering until the Z voltage is in the middle of its range.
+    * Lower the tip down towards the sample by shortening the front leg of the MFP-3D tripod. Watch the measured amplitude as you do this. Also watch the camera image. As the surface comes into focus (before the amplitude starts to drop), consider moving to a clean place on your sample (use the x-y stage coarse positioning micrometers).
+    * If you have a clean landing area for your tip, continue lowering the tip down towards the sample. The amplitude will drop as you near the surface. The computer will beep when feedback kicks in to stop the amplitude from dropping below the setpoint. Continue lowering until the Z voltage is in the middle of its range.
     * If the Z-voltage goes down instead of up, re-tune. If that doesn't fix it, you might have junk stuck to the tip.
     * Lower the 'Set Point Voltage' by about 10%.
@@ Line 103: / Line 113: @@
   - Leave controller and PC running unless expecting a power outage
 ===== Imaging rules of thumb =====
-It is easiest to get a good image on a small scan area (~ 1 micron). 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). 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.
 **Beginner settings**
-  *Scan size 1 micron
+  *Scan size 2 micron (look at a random small feature on a flat background to verify the sharpness of the tip)
   *Scan rate < 15 micron / s
   *Integral gain 10
-  *Free amplitude 1 V (~ 100 nm)
+  *Free amplitude 1 V (corresponds to a cantilever motion of ~ 100 nm)
-  *Set point amplitude 0.65 V
+  *Set-point amplitude 0.75 V
+Sometimes the image is improved by lowering the set-point amplitude a few clicks. For example, this might fix parachuting.
+Sometimes the image is improved by withdrawing and re-running the autotune procedure (the resonant frequency might have changed).
-**Rule of thumb: "One high quality slow scan is worth ~5 low quality fast scans."**
+When you withdraw from the surface, check the free air amplitude is the same as you when you first tuned the tip.
-It is tempting to be impatient and try to 'tune' the imaging parameters to get the data you want from a 2 - 5 minute scan. This strategy often backfires though, if you need to return to old AFM images and find they are junk aside from the information you 'tuned' the parameters for. Also, 'tuning' these parameters in the first place probably takes ~10 minutes so you're not really saving time anyway. The best fix for many imaging problems is simply to lower the 'rate'. The price you pay is scan time. However, I've found that you actually save time (and headache) by taking a single high quality slow scan rather than a bunch of quick ones with little parameter adjustments in between. I find that adjusting the rate so that the scan speed is <10 micron/sec works well in nearly all cases.
+Another thing to try is a slower scan rate. The price you pay is scan time. However, I've found that you actually save time (and headache) by taking a single high quality slow scan rather than a bunch of quick ones with little parameter adjustments in between. I find that adjusting the rate so that the scan speed is <10 micron/sec works well in nearly all cases.
 **Using nanotubes as a diagnostic tool**