Differential tunneling spectroscopy simulations: Imaging surface states

We present a method to simulate scanning tunneling spectra on metal and semiconductor surfaces. The method is based on the full electronic structure of the surface and the tip. Compared to existing methods, it provides the additional advantage that surface and tip contributions can be clearly distinguished in the ensuing spectrum. Analyzing the spectra of surface states on (111) noble metal surfaces, we find-that the simulations agree well with experimental data only with respect to the surface contributions. We conclude that model tips in spectroscopy simulations have to be modified compared to the tips used in topography simulations in the past.