Element-specific contrast in scanning tunneling microscopy via resonant tunneling

Abstract

An element-specific version of scanning tunneling spectroscopy for metals is presented. Contrast between two metals is achieved by resonant tunneling via surface states and image states. These states are characterized independently by inverse photoemission. Image states provide elemental identification via the work function, since their energy is correlated with the local work function. Element-specific surface states produce contrast at higher spatial resolution, but the contrast is smaller than that for image states. These imaging techniques are used to study the growth modes of Cu stripes on stepped W(110) and Mo(110) surfaces.