Structure and contrast in scanning tunneling microscopy of oxides: FeO monolayer on Pt(111)

Abstract

We applied electron-scattering quantum-chemistry theory to investigate the origin of contrast in scanning tunneling microscopy images of iron oxide grown on Pt(111). We show that (a) image contrast and surface topography are not directly related; (b) the maxima in the images occur over O positions for Pt tips and over Fe positions for O-terminated tips; (c) the short-range corrugation is always due to O ${p}_{z}$ orbitals, with a small but important contribution of Fe; and (d) the state that carriers most of the tunneling current is located near the Fermi level and is made mostly of O ${p}_{z}$ and Fe $3{d}_{z2}$ orbitals.