Energy-loss near-edge structure (ELNES) and first-principles calculation of electronic structure of nickel silicide systems

The electronic structures of nanometre-sized nickel silicide systems, Ni2Si and NiSi, have been studied by energy-loss near-edge structure (ELNES) and first-principles band structure calculations. Experimental ELNES of Ni L3- and Si L2,3-edges could be explained well using theoretical spectra calculated for the ground state without the core hole, suggesting metallic properties for both silicides. It was shown that a slight difference in ELNES spectra of Ni2Si and NiSi comes from the coupling among the Ni d and Si p, d states in the unoccupied bands. The density of states and the contour plots of all the valence electron densities for Ni2Si, NiSi together with NiSi2 show that Ni2Si has the bond with the strongest covalent character between Ni and Si atoms and the most transition metal-like character of the Ni 3d band among the three silicides.