Effects of preparation conditions on the optical properties of niobium oxide thin films

Major deposition parameters, including oxygen partial pressure and substrate temperature maintained during film deposition, affect the optical properties of electron beam evaporated niobium oxide films. All the films deposited were found to be amorphous as revealed by the X-ray diffraction study. A method requiring measurements at normal incidence of transmission from two films of different thicknesses prepared under identical conditions was used to determine the optical constants. Substantial changes in the optical constants and optical bandgap energy were observed following changes in the preparation conditions. These variations are related to the corresponding compositional changes, as observed by Rutherford Backscattering Spectroscopy, in the atomic ratio of oxygen to niobium in the films prepared under different conditions.