Short-range electrostatic interactions in atomic-resolution scanning force microscopy on the Si(111) 7×7 surface

Abstract

A low-temperature scanning force microscope (SFM) operating in ultrahigh vacuum was used to study the interaction between a sharp but unreactive oxidized silicon tip and a Si(111) 7×7 surface. Weakly corrugated but, nevertheless, atomically resolved images were obtained over a relatively large range of tip-sample distance. The measured short-range interaction potential and image contrast can be explained by an electrostatic interaction that results from a dipole moment induced in the tip by the distribution of electronic charge among the dangling bonds on the surface. The experiments presented here demonstrate the potential of SFM to quantitatively map even weak, physical interactions with atomic scale resolution. Such experiments should lead to a better understanding of surface reactivity and local charge-transfer effects induced by adsorbates or defects at surfaces.