Energy analysis for island formation on Stranski-Krastanow systems

Abstract

In this thesis, we study the formation of the SiGe nano-islands on the Si substrate from the energy point of view. Our energy analyses are based on a continuum three-dimensional model for the SiGe/Si system, and the analyses are carried out by employing the firrst-order boundary perturbation method to calculate the energy change during the island formation process. Three important issues are investigated. The first one is the critical thickness of thewetting layer below which the formation of islands is completely suppressed. The second issue is the shape transition from a shallow bump to a faceted pyramid, and of particular interest is the dependence of the shape transition on the island size, the island shape and the film thickness. The third issue examined in this thesis focuses on the cooperative formation, which is characterized by the development of trenches surrounding the pyramid island after the bump-pyramid transition.