Investigating Electronic Structure With a Novel Cryogenic Electron Tunneling Microscope*

We report on the development and initial testing of a low-cost cryogenic z-axis tunneling microscope (cryo-ZTM) designed to increase access to nanoscale electronic measurements in undergraduate laboratories. This instrument operates at both room temperature and liquid nitrogen temperatures (~77 K), allowing for direct investigation of low-temperature phenomena such as high-temperature superconductivity. We have collected I–V tunneling spectroscopy data across both temperature ranges on calibration samples including highly oriented pyrolytic graphite (HOPG), gold, and highly doped silicon. These measurements revealed material-dependent differences in tunneling behavior and provided insight into the local electronic structure of each material, with observed responses aligning well with theoretical expectations. The silicon sample displayed asymmetry possibly due to Schottky barrier effects. Ongoing work aims to extend these capabilities to superconducting samples, with the potential to explore features such as the superconducting energy gap and pseudo gap. By developing this system using accessible components and methods, our project supports the broader goal of democratizing advanced experimental tools in condensed matter physics education and research.