LOW-TEMPERATURE REACTION OF BURIED METAL SILICON INTERFACES - THE EVOLUTION OF INTERFACIAL STRUCTURE

Little is known about the initial stages of solid state reactions due, in part, to the lack of suitable experimental probes of buried interfaces. In this paper, the evolution of iron-silicon and titanium-silicon interfaces with temperature and time was investigated by taking advantage of the unique properties of multilayer composites. The structure of the interfaces was monitored by following the changes in the intensities of the Bragg reflections resulting from the superlattice structure. In iron-silicon thin-film multilayer composites, a gradual decrease in diffusion rates and repeat unit size with time, suggest the elimination of unstable configurations with annealing. In titanium-silicon composites, the evolution of the interfaces was much more complex. The repeat unit of the multilayer was found to decrease by 16% during annealing. Even more striking was the development of a compositional plateau at the interface. On the basis of the behavior of these interfaces, a mechanism for the initial stages of a solid-state reaction is presented.