Electronic Transition-Related Optical Absorption in Vanadia Films

Abstract

Vanadium pentoxide (vanadia) is a wide band gap semiconductor. Its layered orthorhombic structure consists of alternating sublayers of V+O atoms and 0 atoms (vanadyl 0) alone aligned perpendicular to the b-axis. This unique structure makes vanadia a useful host for alkali atom intercalation for electrochromic applications, and therefore, an understanding of its optical properties is important. Here, we study the optical absorption characteristics of vanadia in the incident photon energy range E=2.5-6.0 eV (X=490-200 nm). The material is in the form of 0. ltm thick films sputter deposited in Ne/O 2 discharges. Two types of films were studied: single-oriented films with the b-axis perpendicular to the substrate, and amorphous films with an oxygen deficiency. The optical absorption coefficient, oc(E), was determined and interpreted in terms of the structure of the V 3d conduction band. Amorphous, O-deficient vanadia were examined for room temperature aging and were found to oxidize and increase in transmittance in the photon energy range studied.