STM images of molecularly and atomically chemisorbed oxygen on silver

Surface Science Letters 522 L27, (2003)

F. Olsson, M. Persson, and N. Lorente,
Department of Applied Physics, Chalmers/Göteborg University, S-412 96 Göteborg, Sweden

Abstract

We present a theoretical study of scanning tunneling microscopy (STM) images of two chemisorbed, molecular precursors of O2 and chemisorbed O on Ag(110). The electronic structure and the equilibrium geometric structure of the these precursors were obtained from density functional calculations and STM images were calculated from the Kohn-Sham wave functions using the Tersoff-Hamann approximation. This study provide a quantitative analysis of molecular contrast versus molecular orientation, tip-surface distance and character of tip orbital. Our calculated STM images are in good agreement with experimental STM images. We explain the large separation between the experimentally observed protrusions compared to the O--O bond distance using the vacuum tails of a model wave function for an antibonding state of O2.