Formation of thin silicide films on Ta and Nb surfaces

The mechanism of thin silicide film growth on Nb and Ta surfaces depended on the substrate temperature. At room temperature the layer-by-layer growth of Si on Ta and Nb took place. The surface density of Si in one monolayer was 9.3.10/sup 14/ at/cm/sup 2/ on Ta and Nb. The onset of the penetration Si into Nb and Ta was observed at T>900 K. At this temperature the composition NbSi/sub 2/ and TaSi/sub 2/ were formed. At temperature T>1360 K for Ta and T>1270 K for Nb a structural phase transition occurred and silicide Ta/sub 4/Si and Nb/sub 4/Si was formed after reaching a certain critical concentration of Si in the subsurface region. Phase transition was followed by increase of the Si atoms diffusion from the surface into the bulk.