Nanostructuring in Ni/SiC reaction layers, investigated by imaging of atomic columns and DFT calculations

Formation and structuring of the product phases of solid state reactions between nickel and silicon carbide were evidenced by high resolution electron microscopy (HREM), as well as by high angle annular dark field scanning transmission technique (HAADF-STEM) allowing the element-sensitive Z-contrast. The observed preferential orientation relationships between precipitated graphite and δ-Ni2Si as well as between the silicide and the 6H-silicon carbide substrate could be explained by epitaxial relations between the corresponding phases. The diffusion-related mechanisms of the carbon precipitation were investigated in the framework of density functional theory (DFT), yielding information on the diffusion barriers and preferential diffusion directions of carbon atoms in δ-Ni2Si. The calculated driving forces for solution and precipitation of carbon within the silicide phase are discussed.