• git repository with technical documentation
• Lab Notes

The scanning head of our STM uses 3 piezo actuators oriented along the 3 cartesian axes. We currently do not have data on their actuation range.

The tip is made from tungsten wire and mounted to the scanning head using a screw terminal.

To be documented.

The STM mount consists of two aluminum plates which seat against each other precisely using a kinematic mount made from 3 micrometer screws.

The tip/probe is mounted slightly in front of two of the screws with the last one sitting very far back. This makes a fulcrum with the back screw having even more fine adjust (factor 20).

Thread pitch of micrometer screws (according to lab book 16.3.2012):

• Front 0.25mm per revolution
• Back is hence 0.0125mm per revolution or 12.5µm

The control loop for running the STM in constant current mode is currently an entirely analog design. There is a transimpedance amplifier which preamplifies the tunneling current with a gain of 10⁹ V/A. This nicely maps pA to mV (and measured tunneling currents are in the hundreds of pA range).

Learn more about the electronics here: https://git.fa-fo.de/fafo/k8ik-stm/src/branch/main/Electronics

We have built ourselves a simple passive vibration isolation using tension springs and a large mass. The intended damping element (an eddy current brake) did not end up working, but also wasn't really needed after all.

We have not measured performance, but the real world resonance frequency matches the calculations quite well. Here is the calculated transmissibility (blue curve):

There are quite a few other DIY/open STM builds out there. Here are a few links for further reading:

• Open STM — Weilin Ma (2023)
• 3D-Printed STM — MechPanda (2023)
• The PVC Scanning Tunneling Microscope — Tom Ekkens (2018)
• Project „20 steps“ into the microcosmos — Jo Niemeyer (2009) (archive.org)
• Homebrew STM — Jürgen Müller (2006)
• STM References Overview — Jürgen Müller (2006)