Theory of scanning tunneling microscopy of oxygen-adsorbed Ag(110) and Cu(110) surfaces

Abstract

Though recent observation of scanning tunneling microscopy (STM) images of Ag(110) (n×1)–O(n=1,...,7) surface revealed the unique added row structure, detailed atomic arrangement for this model has been an open question. In previous work, the optimized geometries for the (2×1) and (3×1) oxygen-adsorbed surfaces by the first-principles local density functional approximation (LDA) have been determined. The STM images for various bias voltages and scanning tunneling spectroscopy (STS) spectra are calculated for this optimized structure based on the theoretical simulation method by LDA developed in this group. The results reproduced well the clear ridge structure along the added row. Though the oxygen atom is closer to the tip, Ag atoms are more highlighted for the surface positive bias. On the other hand, the local density of states map shows the maximum amplitude at the O site. This strange feature can be explained by the effect of the tip electronic states. The similar calculation has also been performed for the Cu(2×1)–O surface and different characteristics of the substrate structure are found, which might explain the absence of the repulsion between added rows in this surface. The STM images and STS spectra are calculated for the optimized structure.