First-Principles Study of the Step Oxidation at Vicinal Si(001) Surfaces

Abstract

By carrying out ab initio total-energy and electronic-structure calculations, possible initial oxidation structures at vicinal Si(001) surfaces with alternate single-layer SA and SB steps were studied. A new oxidation structure that is more stable than the previously proposed backbond-oxidation models on flat terraces of Si(001) was found. The new oxidation structure is located at the rebonded SB step and consists of a –Si–O– chain structure aligned along the step edge. This chain structure was found to be able to effectively reduce the number of dangling bonds (DBs) at the step edge. This indicates that the reduction of the number of the step-edge DBs plays a crucial role in the formation of the oxidation complex at steps with the local strain. For more detailed information, the electronic properties of the oxidation structure that was found therein were also determined. The calculated site-projected density of states and the scanning tunneling microscopy images of the oxidation structure were found to be clearly distinct from those of the clean vicinal Si surface.