Observations on the hexagonal form of MoSi2 and WSi2 films produced by ion implantation and on related snowplow effects

Abstract

MoSi2 and WSi2 films produced by As-ion implantation through the respective metallic films deposited on Si substrates were analyzed by backscattering and x-ray diffraction. The backscattering results indicate that As atoms are snowplowed into Si during the formation of the silicides. Crystallographic observations on similar samples both before and after various heat treatments provide evidence for the existence at low temperatures of the hexagonal phase of WSi2, presumably unreported up to now, which is similar to the corresponding phase of MoSi2. In the case of the W disilicide, however, the temperature for the transition, hexagonal to tetragonal, is so low that the low-temperature phase is unlikely to be obtained by the usual diffusion-controlled mechanisms.