Structures and Electrical Conduction on Silicon Surfaces

Abstract

With a variety of surface superstructures formed on silicon surfaces, we have clarified close correlations between the atomic-scale structures on surfaces and surface electrical conduction phenomena. In particular, we have succeeded for the first time in experimentally confirming the electrical conduction via surface-state bands that are inherent in the surface superstructures. An important phenomenon has also been found that atoms adsorbed on the surface donate the carriers into the surface-state band, resulting in remarkable enhancement in conductivity. The ultimate two-dimensional electron systems made up from surface-state bands, which was revealed by our study, are expected to provide a new stage in surface physics as well as a precursory stage leading to atomic-scale electronics devices. This article is an introductory part, followed by a main part on the next issue. Here, two of our sample surface superstructures, Si(111)-7×7 clean and Si(111)-√3×√3-Ag surfaces, are introduced in detail on their atomic and electronic structures. Then, fundamentals on electrical conduction near semiconductor surfaces and our experimental methods are described. Based on these introductions, the article on the next issue will describe our main results on the electrical conduction through surface-state bands.