Tip-to-surface distance variations vs voltage in scanning tunneling microscopy

Abstract

This paper presents an experimental and theoretical study of distance vs voltage characteristics of Au/Au tunnel junctions in air and UHV. Qualitative and quantitative results are compared with the classical models of Tersoff and Hamann and Simmons. To fit experimental conditions, the Simmons model has been extended in three dimensions using a hyperboloidal tip. However, a large discrepancy between theoretical and experimental quantitative results has been found in air because of barrier height lowering due to electrode contamination. An experimental rescaling factor is used in the modified Simmons model to fit any $s(V)$ curve with high accuracy. These results are mainly interpreted in terms of gold surface elastic deformations.