Interfacial reactions of crystalline Ni and amorphous SiC thin films

The initial interfacial reactions of crystalline nickel and amorphous silicon carbide (Ni/a-SiC) thin films were investigated by means of X-ray diffraction (XRD) analysis, high-resolution transmission electron microscopy [(HR)TEM], Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). Upon annealing at 500 °C, in the initial stage (< 5 min) of reactive interdiffusion, dissociation of a-SiC takes place, followed by rapid formation of a crystalline nickel silicide sublayer adjacent to the surface and precipitation of (amorphous) carbon, as a sublayer underneath the top silicide layer, as demonstrated by HRTEM. Diffusional transport of Ni through the a-C sublayer and its subsequent reaction with a-SiC leads to the formation of a second silicide layer and a second a-C layer underneath this second silicide layer, etc. As a result, the interfacial reactions lead to the formation of an alternating, nickel silicide/amorphous carbon (a-C), multilayered structure: silicide/a-C/silicide/a-C/silicide/a-SiC. The microstructural development was interpreted on the basis of the thermodynamics and kinetics governing the reaction.