Electronic properties of metals chemisorbed on semiconductor surface and metal/semiconductor interfaces

The understanding of chemical reactions which occur at the interface between metal and semiconductor is of both practical significance and theoretical interest. However, due to the difficulties of studying solid-solid reaction on an atomic scale, the mechanism responsible for those reactions remains somewhat unclear. There still exist some controversies regarding whether metal-semiconductor junctions are abrupt or not. In the present article, chemisorption geometries and electronic structures of group III metals, noble metals, transition metals and rare earth metals on semiconductor surfaces are reviewed and discussed from the theoretical point of view. Since most extensive experimental studies have done on Si(111) and GaAs(110) surfaces, more detailed discussions will be devoted to chemisorptions on those cleaved surfaces, such as Al/Si(111), Al/GaAs(110), Ag/Si(111), Ni/Si(111), Mo/Si(111) and interfaces of transition metal silicide and silicon. For studying chemisorbed surfaces and interfaces both slab models and cluster models are used, and results from both the first principle method and the empirical method are presented. In many cases, where local properties are emphasized, a cluster consisting of a finite number of atoms is quite adequate for simulating a semi-infinite surface. Although the first principle calculation is more accurate, however, it is quite expensive and time consuming, and the empirical method still can offer reasonable results for comparing with data from experiments.