Investigation of Si1-xGex alloy formation by using STM

Abstract

In this thesis, initial stages of SiGe alloy growth on the Si(001)(2x1) surface are analysed by Scanning Tunneling Microscopy (STM). Design and construction of an Ultra High Vacuum (UHV) surface analysis/preparation chamber and a UHV-Scanning Tunneling Microscope are also decribed. The Si subscript 0.36 Ge subscript 0.64 alloy was epitaxially grown on the silicon substrate at various coverages (0.1-3.6 ML) and at different temperatures (ca. 300-500 degrees C). The growth was almost one dimensional preferring the direction perpendicular to the underlying silicon dimer rows at the low coverages. Anti-phase boundaries were observed to lead multi-layer growth. Strong interaction between the overlayer and the substrate was found to buckle the substrate dimers. Different growth mechanisms, island formation and step flow, were identified at low and high temperatures. (2xn) ordering of the strained overlayer was only observed at an intermediate temperature (ca. 400 degrees C).