ARE ELECTRONIC INTERFERENCE EFFECTS IMPORTANT FOR STM IMAGING OF SUBSTRATES AND ADSORBATES - A THEORETICAL-ANALYSIS

The electron scattering quantum chemical (ESQC) method is used for the analysis of the influence of interference effects in the STM image formation process. This method is based on a direct calculation of the multichannel scattering matrix for the electron tunneling through the STM gap and is therefore adequate for this detailed interference analysis, in contrast with the usual local-density-of-states (LDOS) approximation. Graphite is shown to be a simple two-channel system with no interference effect in the tunneling process. Therefore, the image obtained with a scattering matrix approach correspond to the LDOS calculation. On the contrary, electronic interferences between through-space and through-molecule tunneling are essential for the STM image of adsorbates, as shown with the example of benzene on rhodium. In these cases, scattering matrix calculations are valuable because of their capability to correctly reproduce the interference effects.