AVS 46th International Symposium
    Surface Science Division Thursday Sessions
       Session SS2+EM+NS-ThM

Paper SS2+EM+NS-ThM10
Novel Growth Behavior of Ge on Pb Covered Si(111) Surface

Thursday, October 28, 1999, 11:20 am, Room 607

Session: Nucleation and Growth
Presenter: T. Tsong, Academia Sinica, ROC
Authors: I.S. Huang, Academia Sinica, ROC
T.C. Chang, Academia Sinica, ROC
T. Tsong, Academia Sinica, ROC
Correspondent: Click to Email
A surfactant can modify the growth behavior of a system to our advantages. We report discovery of a novel growth behavior in a Pb-layer promoted growth of Ge on Si(111). For this system, not only can Ge atoms grow on Si(111) surface layer by layer for many layers, but the growth behavior is contrary to traditional nucleation and growth theory and most experimental results in epitaxy. This growth is not governed by the reaction-limited-aggregation (RLA) process at low temperature as has been found in traditional epitaxy. The most interesting feature we find is that a compact-to-fractal island shape transition occurs when the sample temperature is increased, or the deposition flux is decreased. In traditional epitaxy, fractal growth occurs by diffusion-limited-aggregation (DLA) at low temperatures, thus fractal growth will disappear as the sample temperature is raised to the extent that step edge diffusion can occur. Our observation demonstrates that fractal islands can also be grown by RLA, and the importance of reactions in aggregation of Ge atoms in this system. Earlier theories neglect the reaction processes which may be acceptable for metal-on-metal systems, but are not good enough for other systems. Our result points to a need to develop a more complete nucleation theory where both diffusion and reaction are properly taken into account.