VUV stimulated solid-phase reactions on the surface of Ni nano-layers on Si substrate

Using X-ray reflectometry method, the kinetics of solid state reactions at the surface of layered thin film nickel/Si-sub system (effective nickel thickness 15 and 45 nm) under VUV irradiation of 8 <= hv <= 1.8 eV energy was studied. Nickel and nickel oxide layers have shown no changes both in thickness and density. As a result of VUV stimulated silicon diffusion from the substrate and of its reaction with nitrogen, a new layer of silicon nitride with of (3.2...3.4) g.cm(-3) density is formed at the nickel film surface. The silicon nitride formation reaction, where nickel acts as a catalyst, is of zero order typical of radiation-(photo)-chemical processes and stops at the layer thickness about 1.5 nm. After aging in air, the surface layer density decreases down to 2.3 g.cm(-3) and thickness increases to about 25 nm due to oxidation. Repeated cycles of irradiation and oxidation result in degradation of the film-substrate system due to breaking the film adhesion.