Oral: Installation of low temperature transimpedance amplifiers to improve the performance of a scanning tunneling microscope

Scanning tunneling microscopy (STM) is a well-established technique used to study and characterize the topographic and electronic properties of material surfaces with atomic resolution. We outline an undergraduate research project aimed at restoring and improving the performance of a custom built low-temperature STM. Along with diagnosing and troubleshooting various system components, this restoration involved the building of an in-situ transimpedance amplifier to boost system signal-to-noise ratio (SNR). We conducted a survey to identify a commercially available op-amp candidate that was high vacuum compatible, low-temperature compatible, had sufficiently high bandwidth, and had low input bias. We then carried out ex-situ Bode plot analysis of op-amps in liquid nitrogen to screen for the best performing devices. Multiple rounds of compatibility and installation design testing were performed, followed by a final installation and a significant reduction in 60Hz noise in tunnelling current. Using the installed amplifier, we demonstrate atomic resolution and spectroscopy capabilities, at room temperature and at low-temperature (77K). Finally, we use the instrument to carry out STM measurements of epitaxially synthesized 2D quantum materials.