Multivalence states and optical band-tail effect in heavily V-doped ZnS thin films

Abstract

Abstract V K-edge X-ray absorption near edge structure spectroscopy analysis of Zn1-xVxS shows that the bulk V valence states change from V(IV) to V(II) as the V concentration increases from x = 0.15 to x = 0.48. Atomic bound-state transitions from the hybridization of sp ZnS and 3d V electronic states show a decreasing hybridization with V concentration. X-ray photoelectron spectroscopy reveals the coexistence of a V(IV)/V(III)/V(II) mixture at the surface with a predominant V(III) state, indicating differences between surface and bulk. Optical studies show large band-tails associated with in-gap defects that increase with V concentration.