FORMATION OF VANADIUM SILICIDES AT THIN-FILM INTERFACES

Previous results have shown, in agreement with the silicide-growth theory of Walser and Bené, that VSi2 is the first silicide phase to nucleate and grow at single-crystal-Si-V interfaces. We have found that with sputtered thin-film-V-crystalline-Si or amorphous-Si diffusion couples we can reproducibly cause either VSi2 or V3Si, respectively, to nucleate and grow. V3Si and VSi2 are never observed together, suggesting that bistable growth can be triggered by the initial interface. The V3Si growth was found to have a t1/2 dependence and V was found to be the dominant diffusing species. This implies that unlike the case of VSi2, in V3Si the diffusion constant of V is much larger than Si and growth occurs at the Si-V3 Si interface. Deposition parameters and initial sample properties such as structure and impurity content which may control the nature of the reaction phase are discussed. We also find oxygen to be rejected by a growing A-15 phase. Samples were studied by Rutherford backscattering, Seeman-Bohlin x-ray diffraction, and electrical-resistivity-vs-temperature measurements.