Theoretical Analysis of Tip Effect on Noncontact Atomic Force Microscopy Image of Si(100) 2×1: H Surface

Abstract

The influence of the tip structure on the noncontact atomic force microscopy (nc-AFM) image of a hydrogenated Si(100) 2×1 surface is revealed by a theoretical simulation with the first-principles density functional approach. Two different Si tips, i.e., a clean Si(111) tip and a hydrogen terminated Si(111) tip, are modeled by SiH3 and SiH4 clusters, respectively, and the simulated nc-AFM images are compared for the respective tip models. The clean Si tip produced a much larger corrugation amplitude than the hydrogen-terminated Si tip. For the latter tip, a marked change in the image is observed with the approach of the tip turning point towards the surface. When the tip turning point becomes very close to the surface, the inversion of the brightness of the image is found to appear.