Color mapping by scanning tunneling microscopy: Chemical analysis of metal surfaces

Abstract

We present true color maps of a metal surface imaged by scanning tunneling microscopy (STM). Light emission spectra were acquired at each imaging pixel, and converted into a real color map. A rough gold film was shown to exhibit minimal color changes across the sample, so spectra are dependent on material and not sample geometry, due to a small radius tip. A larger tip was still able to distinguish between Ag and Cu clusters with ∼10 nm resolution, despite the onset of geometric effects. We conclude that color mapping represents an ideal way of identifying metals in STM on the nanometer scale.