EPITAXY OF FLUORITE-STRUCTURE SILICIDES - METASTABLE CUBIC FESI2 ON SI(111)

Epitaxial FeSi2 of cubic symmetry has been grown for the first time on Si(111) by solid phase epitaxy (SPE) and molecular beam epitaxy (MBE). Structural investigation by reflection high-energy electron diffraction (RHEED) and transmission electron microscopy (TEM) suggest the phase to have the same CaF2 structure as CoSi2 and NiSi2. Ultraviolet photoelectron spectroscopy (UPS) and resistivity measurements show that the phase is metallic and undergoes an irreversible metal/semiconductor transition to the orthorhombic beta-FeSi2 phase at a temperature depending on the thickness of the film. Hall effect measurements have revealed holes to be the dominant carrier species. High-resolution TEM studies, together with the observation of an anomalous Hall effect as well as theoretical considerations, indicate that this cubic FeSi2 phase is magnetic, in contrast to CoSi2 and NiSi2.