X-Ray Absorption Study of the Metal-Nonmetal Transition in NiS and Ni1-xMxS (M=Fe and Co)

Abstract

We have studied the electronic structure of NiS using Ni 2p X-ray absorption spectroscopy and subsequent clustermodel analysis. The results indicate that with Fe substitution or with decreasing temperature, the S 3p-to-Ni 3d chargetransfer energy increases and the Ni 3d-S 3p transfer integral decreases leading to the increase in the band gap and with Co substitution the band widths increase through the Ni 3d-to-Co 3d hybridization leading to the collapse of the band gap.