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

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 similar to10 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. (C) 2002 American Institute of Physics.