Diffusion of silicon in Pd2Si during growth

Abstract

The diffusion of silicon in Pd2Si during silicide formation has been studied with the aid of radioactive 31Si. Annealing samples with the structure Si〈 〉/31Si/Pd at 350 °C produces Pd2Si in which the 31Si is broadly distributed throughout the silicide, thereby indicating a very high silicon self-diffusion in Pd2Si during silicide formation. Since silicon self-diffusion in Pd2Si in the absence of growth is low at these temperatures, this suggests that silicon diffuses by a vacancy mechanism during polycrystalline Pd2Si growth. If samples with the structures Si〈111〉/epitaxial Pd2Si/31Si/Pd are annealed at the same temperature, the 31Si is found to be broadly distributed throughout the subsequently grown Pd2Si, but very little diffusion of 31Si back into the epitaxial region is observed. It is argued that a silicon vacancy mechanism is the most probable diffusion mechanism to have produced the observed 31Si distribution and it is therefore proposed that silicon diffuses by a vacancy mechanism in both polycrystalline and epitaxial Pd2Si growth.