Interface structure of ultrathin CoSi2 films epitaxially grown on Si(111)

The interface structure of ultrathin CoSi2 films grown on Si(111) was inves tigated by quantitative low-energy electron diffraction. Codeposition of th e elements leads to a film composed of domains with two and three Si-Co-Si trilayers in CaF2 structure. As within the film, Co atoms at the interface are eightfold coordinated. The lateral unit cells of the film and substrate are mutually rotated by 60 degrees (B-type orientation). The interfacial t rilayer is substantially distorted, its distance to the substrate expanded, and its sublayer spacings considerably modified from the bulk. Also, the s ubstrate's top spacing is expanded. The results compare almost quantitative ly with recent density-functional calculations. (C) 2000 American Institute of Physics. [S0003-6951(00)04306-0].