Niobium pentoxide (Nb2O5) thin films: rf Power and substrate temperature induced changes in physical properties

In the present work, thin Nb2O5 films were grown on glass substrates using rf magnetron sputtering technique, in a pure argon atmosphere at different rf power and various substrate temperatures. X-ray diffraction result revealed the amorphous nature of deposited films. The maximum optical transmittance of about 92% with clear interference pattern was realized from the optical study. A systematic reduction in energy band gap values with increasing substrate temperature and rf power could be attributed to the localized state near the band edges. This hypothesis is consistent with our photoluminescence study where we observe the slight shift in emission peak towards higher wavelength region due to the effect of optical band gap narrowing. The X-ray photoelectron spectroscopic study confirms the film purity and the presence of five-valent niobium (Nb5+) in Nb2O5 films. Surface morphological studies revealed the formation of Nb2O5 films with smooth, uniform and pinhole free in nature. Raman spectra show the NbO stretching mode of the deposited films.