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

This paper presents an experimental and theoretical study of distance vs vo ltage 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 result s has been found in air because of barrier height lowering due to electrode contamination. An experimental rescaling factor is used in the modified Si mmons model to fit any s(V) curve with high accuracy. These results are mai nly interpreted in terms of gold surface elastic deformations. [S0163-1829( 99)11635-7].