Optical behavior of sputter-deposited vanadium pentoxide

Abstract
A series of V–O alloy films were sputter deposited on glass substrates using a vanadium target and rf-excited Ar/O2 discharges containing 2%–8% O2. On the basis of x-ray results, the films were nominally identified as vanadium pentoxide. Optical transmission and reflection characteristics were measured by double-beam spectrophotometry in the 390- to 700-nm-wavelength region. From these measurements, the absorption coefficient α was determined as a function of the incident photon energy hν. The absorption edge of all films showed two distinct regions of behavior: a high photon energy region in which α varied linearly with (hν)2 and a low-energy tail. The behavior of α is discussed in terms of the structural and electronic changes in the films due to nonstoichiometry and compared to results obtained for single crystal V2O5.