Reactive deposition epitaxy of CrSi 2

Abstract

CrSi 2 layers were synthesized by deposition of Cr onto a Si(111) substrate kept at 450°C, allowing full reaction of the metal with silicon. In situ RHEED patterns confirmed the formation of the CrSi 2 phase with matching faces CrSi 2(0001)/Si(111) and of the type A azimuthal orientation CrSi 2 <10 1 0> ‖ Si<110>. The epitaxy of the initially textured films is enhanced by post-deposition annealing up to 1200°C. With high-temperature treatment, the initially nearly continuous silicide layers break up into CrSi 2 islands, the height and diameter of which increases with the annealing temperature. Backscattering spectra confirm the presence of exposed silicon, by indicating that the apparent stoichiometry of the film is Si rich CrSi x ( x > 2). In the best case, a minimum channeling yield lower than 30% was found in the Cr signal of the backscattering spectrum. As far as we know, this is the first evidence of channeling in CrSi 2 films grown by any technique, other than ion beam synthesis. Both the areal fraction of exposed Si and the crystalline quality of the silicide islands depend strongly on the annealing temperature and the amount of Cr deposited. From perpendicular strain measurements, the critical thickness for pseudomorphic growth is estimated to be the equivalent of 20 Å of deposited Cr.