Surface structure of thin epitaxial CoSi sub 2 grown on Si (111).

The surface structure of single crystal, epitaxial, thin film, CoSi sub 2 on Si(111) substrates has been studied by low energy electron diffraction, Auger electron spectroscopy, Rutherford backscattering and transmission electron microscopy. By controlling deposition and annealing parameters, the surface may be reversibly prepared with either of two stable structures which we call the CoSi sub 2 -C and CoSi sub 2 -S. The CoSi sub 2 -C surface appears to be a bulk termination of the CoSi sub 2 lattice with Si as the topmost layer. The CoSi sub 2 -S surface appears to be terminated by an additional bilayer of Si which allows full coordination for all Co and Si layers. A 2 X 2 superstructure is seen by low energy electron diffraction during the transition from the CoSi sub 2 -C to the CoSi sub 2 -S surface. The orientation and stability of the additional bilayer of Si at the CoSi sub 2 -S surface may affect the orientation of epitaxial Si overlayers.