X-RAY-SCATTERING STUDIES OF FESI2 FILMS EPITAXIALLY GROWN ON SI(111)

A laboratory x-ray diffractometer for surface and thin-film studies is presented. Ex situ structural characterization of FeSi2 films epitaxially grown on Si(111) is reported. Both specular and nonspecular reflectivities are measured on beta-FeSi2 films grown by solid-phase epitaxy and reactive deposition epitaxy techniques. A detailed comparison is performed of the electron density profile of the films normal to the surface, as well as of their surface roughness. In-plane diffraction is also measured at grazing incidence. For the beta-FeSi2 sample investigated, the (110) epitaxy on Si(111) is clearly shown. For a film grown by molecular-beam-epitaxy codeposition at 550-degrees-C, the existence of a new metastable phase which is in registry with silicon along the Si[1BAR 10] direction and slightly out of registry, (3.0+/-1.0)% compressed along the Si[112BAR] direction, is reported.