Scanning tunneling microscopy and spectroscopy of reconstructed Si(100) surfaces

We combine theory and experiments to study bias-dependent scanning tunneling microscopy (STM) images of the different reconstructions of Si(100) surfaces. Coupling with the analysis of scanning tunneling spectroscopy (STS) data, we show that STM images result from a subtle interplay between topographic effects and the energy dependence of probed electronic states. We confirm that the second STS peak at positive sample bias arises from the injection of electrons into surface electronic states mainly localized on the dimer's backbonds but also containing π^* and σ components. The comparison between theory and experiments strongly suggests an important role played by tip-sample interactions, through a local modification of the dimer buckling and by the surface band bending induced by the applied bias.