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projects:stm:log [2025/07/13 00:04] – [Day 2025-07-12 (k8ik, rahix)] rahixprojects:stm:log [2025/08/03 15:56] (current) – [Day 2025-08-02 (k8ik, q3k, rahix)] rahix
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 ====== Lab Notes for the Scanning Tunneling Microscope ====== ====== Lab Notes for the Scanning Tunneling Microscope ======
  
 +==== Day 2025-08-02 (k8ik, q3k, rahix) ====
 +Tried imaging the DVD surface under the SEM for reference.  Had a bit of trouble getting an image to become visible -> turns out that the surface is only visible at low acceleration voltages and becomes very invisible the higher it gets.  Finally worked well at 5kV and using SE imaging mode.
 +
 +The samples were prepared by lifting the bottom plastic off the DVD such that the aluminum foil sticks to the remaining plastic which also has the label printed on its back.  So we are looking at the sample from the same side as the DVD drive laser.
 +
 +{{:projects:stm:dvd-surface-uncalibrated.png?400|}}
 +
 +(The dimensions are off, because of our SEM not being calibrated properly)
 +
 +We now know that our samples are good and we should be able to image them on the STM!  Also found some prior art of imaging DVD surfaces with an STM, further corroborating that this approach will work: 
 +
 +  - [[http://www.joniemeyer.com/jo_niemeyer/STM.html|jo niemeyer STM]] ([[https://web.archive.org/web/20210518134908/http://www.joniemeyer.com/jo_niemeyer/STM.html|archive.org]])
 +  - [[https://hackaday.io/project/29332-the-pvc-scanning-tunneling-microscope/log/81900-samples-to-use-on-the-stm|DVD+R imaging on the "PVC scanning tunneling microscope"]]
 ==== Day 2025-07-12 (k8ik, rahix) ==== ==== Day 2025-07-12 (k8ik, rahix) ====
 Rebuilt the experiment to the last state (oscillscope for live viewing, red pitaya for acquisition and x/y control, lab power supply). Rebuilt the experiment to the last state (oscillscope for live viewing, red pitaya for acquisition and x/y control, lab power supply).
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     * The offset seems to throw off the PI controller quite a bit     * The offset seems to throw off the PI controller quite a bit
     * Not able to achieve much stable tunneling     * Not able to achieve much stable tunneling
-  * Tried curring a tip at an angle, but with much less pulling force+  * Tried cutting a tip at an angle, but with much less pulling force
     * Very very good results, achieving tunneling got considerably easier     * Very very good results, achieving tunneling got considerably easier
     * Almost no hysteresis around the probe touching distance, making coarse approach very easy     * Almost no hysteresis around the probe touching distance, making coarse approach very easy
 +    * Hypothesis: The tip is now much more stubby which makes it less prone to bending during sample contact.
  
 Also started to put more effort into making sure the tips are inserted straight into the STM. Also started to put more effort into making sure the tips are inserted straight into the STM.
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 Added a 1k resistor parallel to ''R17'' to increase the X-axis gain from 1 to 11.  This means the input voltage is now -1V to 1V rather than -10V to 10V. Added a 1k resistor parallel to ''R17'' to increase the X-axis gain from 1 to 11.  This means the input voltage is now -1V to 1V rather than -10V to 10V.
 +
 +Managed to take some sweep recordings while the STM was tunneling:
 +
 +{{:projects:stm:2025-07-12_23-34-scan.png?400|}}
 +{{:projects:stm:2025-07-12_23-35-scan.png?400|}}
 +
 +We definitely can't see any surface here, but we could reliably observe that the X movement slowly moved a stable tunneling out of range.
 ==== Day 2025-06-29 (rahix, k8ik, q3k) ==== ==== Day 2025-06-29 (rahix, k8ik, q3k) ====