Vanadium Oxide Overlayers on Vicinal Rh(15 15 13): The Influence of Surface Steps

摘要

The growth of vanadium oxide monolayer films on a vicinal Rh(111) surface has been examined by scanning tunneling microscopy, low-energy electron diffraction, and X-ray photoelectron spectroscopy to determine the role of substrate steps on the oxide overlayer structures. While similar local V-O building blocks as on the flat Rh(111) surface are found on the stepped surface as a function of the chemical potential of oxygen, the effects of the interfacial chemistry of step atoms and of the strain relief at step edges lead to novel oxide structures that are not observed on the extended (111) surface. Specifically, the high chemical affinity of step atoms toward oxygen induces a reorientation of pyramidal VO5 units at high chemical potentials of oxygen generating a unique oblique superstructure near the step edges. For more reducing conditions a (2 X 2) surface-V_2O_3 phase is formed, which is stabilized by the strain relief at step edges and is therefore not observed on the flat Rh(111) surface.