Silicon Systems

Submonolayers

Scanning tunneling microscopy (STM) has provided many breakthroughs in imaging surfaces on the atomic scale. Some of the most notable of these have been for the Si(100) surface, which has great technological importance and also serves as the model semiconductor system for studying atomistic growth mechanisms and electronic properties. Many aspects of homoepitaxial growth on Si(100) and the heteroepitaxial growth of Ge on Si(100) have been thoroughly explored. However, the atomistic mechanisms of the "lateral condensation" of adsorbed atoms to form ordered islands of a new layer are still not well understood. Using STM, we have been looking at topics such as formation of stable nucleus, transition from the stable nuclei to initial small islands, the adatom-adatom and adatom-substrate interactions and their roles in the kinetic pathways leading to the final epitaxial growth [Figure Set 1, Figure Set 2]. Meanwhile we found that the conventional interpretation of Si(100)-2x1 empty-state imaging had to be revised to reconcile with our results [Figure Set 2]. The observed enhancement of STM sensitivity to the surface states and to the surface dimer structural configurations can be satisfactorily explained in the light of this new understanding [Figure Set 3].