Gold-induced nanostructuring of silicon surfaces

Abstract

In this thesis, a combination of scanning tunneling microscopy and low energy electron diffraction is used to investigate how submonolayer amounts of Au affect the large scale surface morphology of a vicinal Si sample miscut from (111) by 8° toward [11-2]. It is found that the structure of this surface is exquisitely sensitive to Au coverage. The surface exhibits nanofacets whose orientation depends critically on the amount of Au deposited. These nanofacets must preserve the total off-axis angle of the wafer. We find that the (775) facet persists over a wide range of Au coverages up to 0.32 ML. The (775)-Au reconstruction is characterized by a self-assembled array of 1-d atomic chains spaced 21.3 A apart and is optimized at a Au coverage of 0.24± 0.03 ML. Oddly, the stoichiometry at optimal coverage incorporates 1.5 Au atoms per unit cell. The persistence of the (775)-Au reconstruction over such a wide range of Au coverages suggests that it is a low energy surface.