STM Spectroscopy on semiconductors

Abstract

The chapter shows the application of scanning tunneling microscope (STM) spectroscopy on semiconductors that helps to get local spectroscopic information on defects, low-dimensional nanostructures, or organic molecules. STM is one of the most powerful experimental tools used to study surfaces, interfaces via cleaved materials, point defects in semiconductors, and organic molecules on metallic or semiconductor surfaces. The tunneling current varies approximately exponentially with the tip-surface separation, increasing by a factor of 10 for every 0.1 nm reduction in the separation. The current is mainly bound to the last atom on the tip, the closest to the sample, and this helps in obtaining the atomic resolution. The chapter also discusses microscopical studies on shallow and deep defects in semiconductors. For deep defects, it takes into account the coupling between the energy level associated with the defect and the conduction or valence bands. This coupling is analyzed in terms of emission and capture rates also used for the electrical characterization of the defects.