4. Methods of Tunneling Spectroscopy

Abstract

Publisher Summary This chapter describes the application of tunneling spectroscopy to probe surface phenomena. Examples are drawn from a few of the earlier applications of scanning tunneling microscopy (STM) that demonstrated the potential for spectroscopy. Tunneling spectroscopy is not a new technique and has been used a great deal in examining the properties of fixed tunneling junctions. With the advent of the scanning tunneling microscope, two new variables come into plays that were not accessible in fixed tunnel junctions. The first, and most important, is the scanning ability of the STM that adds a great potential for atom resolved probing of spectroscopic signals on a material. This ability has allowed investigators to probe the electronic properties, ranging from individual adatorns, on a surface to spatial properties of vortex states of superconductors. The second feature in STM spectroscopy is the variability of the tip-sample separation. This variability allows the probing of the potential barrier between two electrodes and also allows the STM to function as an electron interferometer by changing the electron wave function path length between the sample and the tip. Finally, the chapter concludes that tunneling spectroscopy suffers from the unknown contribution of the probe tip. This can lead to nonreproducibility in data, resulting from tip instabilities, with voltage change, tip composition, and/or structural dependencies.