LAB UNIT 5: Scanning Tunneling Microscopy

Synopsis The STM provides real space atomic resolution images through tunneling current between a conductive tip and a conductive/semiconductive surface. In this lab unit, we employ two STM modes, i.e., constant current imaging mode and tunneling spectroscopy mode, to study HOPG (graphite) and gold (Au). HOPG is one of well studied materials and serves as a standard for STM technique, and the interpretation of the STM images as well as the spectroscopic analysis are debated actively in literatures. Here, taking into consideration of artifacts such as thermal drift, students will determine the lattice constant and the atom-to-atom distances of HOPG. The contrasting spectroscopic data of the HOPG and Au will illustrate the difference in electronic structure between semi-metals and metallic systems.