Formation and Decay of Surface-based Nanostructures: Atomic-scale Understanding
Prof. E. G. Wang
Institute of Physics, Chinese Academy of Sciences, Beijing, China
Surface-based nanostructures are at the forefront of exploratory work for next generation devices, which rely on materials of ever increasing complexity and decreasing size. In most cases these nanostructures must be fabricated through epitaxy. The understanding of the kinetics involved in the formation and stability of these nanostructures on surface is of importance. In this talk, I will show that, when a surfactant layer is used to mediate the growth, a counter-intuitive fractal-to-compact island shape transition can be induced by increasing deposition flux or decreasing growth temperature. Specifically, I introduce a reaction limited aggregation (RLA) theory, where the physical process controlling the island shape transition is the shielding effect of adatoms stuck to stable islands on incoming adatoms. Also discussed are the origin of a transition from triangular to hexagonal then to inverted triangular observed by experiments. Furthermore, I will study the decay characteristics of islands on surface, as the stability of nanostructures after their creation is a critical issue for nanotechnology.