Scanning tunneling microscopy: a critical view of tip participation

Abstract

A model for the scanning tunneling microscope (STM) experiment is presented which explicitly treats the STM tip as a polyatomic crystalline surface. The net tunneling current is the sum of all tunneling occurrences from each tip atom to every substrate atom. With the aid of computer simulations, the atomic resolution of an hexagonally close-packed substrate with a nearest neighbor distance of 0.245 nm is reproduced using an hexagonally close-packed tip with a nearest neighbor distance of 0.277 nm. The resulting periodicity of the image is independent of tip size. The recent observations of anomalous long range periodicity is explained by employing the model in a simulation of a 2.7 nm super lattice.