I recently motorized the coarse approach mechanism on my STM. The coarse approach is done by first fully extending the Z-piezo (reasonably slowly) to search for the surface. If it doesn t find the surface, it fully retracts, and a stepper Continue reading
I finally got around to finishing up the Teensy software for my STM! The Teensy controls scanning, PI control of the Z-axis piezo, sigma-delta modulation of the scanner DAC outputs, and serial communications with a PC. I also wrote a C# Continue reading
I m making some major changes to the Teensy firmware and wanted to share this image of a gold surface I took after making some improvements to the way the scan is generated. Previously, I was just advancing the scan in Continue reading
I m working on a new scan head design using a tube scanner and automated coarse approach. Still a work in progress, but here s a look at what I ve got at the moment: I ve kept the 3-screw coarse approach mechanism since it s Continue reading
Got a tube scanner in the mail today! I paid $100 for it from Boston Piezo Optics, which seemed pretty good. If you want to get a tube from them, just make sure you get one that s in stock as it Continue reading
The unimorph disk scanner is cheap, has low capacitance, and works at low voltages, making it great for a low-cost SPM. It does have one major disadvantage though: poor rigidity, especially in the Z-axis where it s most important. This makes it Continue reading
The STM scanner can be calibrated from atomic resolution images, since the distance between atoms is well known. For the Z-axis, I ll use this scan that I ve taken of a gold surface: Although I m not able to resolve individual atoms in metals, I Continue reading
I ve recently created a PCB for my STM project and updated the electronics page. I m now using digital feedback and linearizing the tunneling current data in software using a logarithmic lookup table. This really stabilized the feedback loop and I m now Continue reading
I recently finished building a scanning tunneling microscope as a hobby project. The inspiration for this project came mainly from seeing John Alexander s simple STM project some time ago. I m a physics PhD student and although I work mainly with Continue reading