1. Theory of Scanning Tunneling Microscopy

Abstract

Publisher Summary This chapter discusses that scanning tunneling microscopy (STM) has proven to be a powerful and unique tool for the determination of the structural and electronic properties of surfaces. While STM was originally introduced as a method for topographic imaging of surfaces, many related techniques have since grown out of it. These include local spectroscopy, scanning potentiometry, and a host of other local probes. It discusses the current understanding of STM and tunnelling spectroscopy. The chapter explains the basic principles of STM— that is, vacuum tunneling and scanning tunneling microscopy. In vacuum tunneling, the potential in the vacuum region acts as a barrier to electrons between the two metal electrodes, the surface and the tip. The transmission probability for a wave incident on a barrier in one dimension is easily calculated. For STM, it is typically needed to consider only the limit of weak transmission, corresponding to the most common range of barrier heights and widths. In scanning tunneling microscopy, a sharp metal tip is brought close enough to the sample surface that electrons can tunnel quantum mechanically through the vacuum barrier separating tip and sample. This tunneling current is extremely sensitive to the gap— that is, to the height of the tip above the surface.