Spectroscopic characterization of electron-beam evaporated V2O5 thin films

Thin films of vanadium pentoxide (V2O5) were prepared by electron beam evaporation at different deposition temperatures. The chemical composition and structural and optical properties were investigated employing spectroscopic techniques, viz. X-ray photoelectron spectroscopy (XPS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), infrared spectroscopy (IR), Raman spectroscopy (RS) and optical spectroscopy (OS). The influence of deposition temperature on the film properties were deduced from the spectroscopic measurements. The room temperature (303 K) electron-beam evaporated V2O5 films were nearly stoichiometric. The films formed at elevated temperatures were sub-stoichiometric as revealed (XPS) from the shift of the V(2p(3/2)) emission peak, the broadening of full width at half maximum (FWHM) and the decrease in the O(ls):V(2p(3/2)) ratio. The shift of vanadyl mode in the IR and Raman spectra, decrease of the optical band gap and increase in the near-infrared-broad band absorption also supported the sub-stoichimetric nature. Annealing of the films formed at T-s similar to 553 K in an oxygen atmosphere (a partial pressure of 10(-4) mbar) at 693 K led to the existence of vanadium in its highest oxidation state. (C) 1997 Elsevier Science S.A.