Direct determination of atomic structure at the epitaxial cobalt disilicide on (111) Si interface by ultrahigh resolution electron microscopy

Abstract

Previously we reported that (111) CoSi2 on Si grown under UHV conditions is a true single-crystalline epitaxy. In this letter we report a determination of the atomic structure at the silicide-silicon interface in UHV reacted films. This determination was based on electron-microscopical data taken on an ultrahigh resolution instrument but included detailed consideration and modeling of the expected images. The atomic arrangement at this interface is best modelled with the silicide atom adjacent to the interface a metal one, with apparently only 5-fold local coordination, contrasted with the 8-fold coordination found in the bulk. The interface is perfectly regular, except at misfit dislocations, which have interesting core structure. Moreover, they provide indirect evidence for the ‘‘5-fold’’ model in the case of codeposited silicide films.