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

1988; American Physical Society; Volume: 37; Issue: 18 Linguagem: Inglês

10.1103/physrevb.37.10786

1095-3795

F. Hellman, R. T. Tung,

Advanced Materials Characterization Techniques

The surface structure of single-crystal, epitaxial, thin-film, ${\mathrm{CoSi}}_{2}$ 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 ``${\mathrm{CoSi}}_{2}$-C'' and ``${\mathrm{CoSi}}_{2}$-S.'' The ${\mathrm{CoSi}}_{2}$-C surface appears to be a bulk termination of the ${\mathrm{CoSi}}_{2}$ lattice with Si as the topmost layer. The ${\mathrm{CoSi}}_{2}$-S surface appears to be terminated by an additional bilayer of Si which allows full coordination for all Co and Si layers. A 2\ifmmode\times\else\texttimes\fi{}2 superstructure is seen by low-energy electron diffraction during the transition from the ${\mathrm{CoSi}}_{2}$-C surface to the ${\mathrm{CoSi}}_{2}$-S surface. The orientation and stability of the additional bilayer of Si at the ${\mathrm{CoSi}}_{2}$-S surface may affect the orientation of epitaxial Si overlayers.