STRUCTURAL, ELECTRICAL AND OPTICAL-PROPERTIES OF SPUTTERED VANADIUM PENTOXIDE THIN-FILMS

Thin films of vanadium pentoxide (V2O5) are prepared by r.f. sputterin g from a V2O5 target in a gas mixture of argon and oxygen under a tota l pressure P-t=P(O-2)+P(Ar)=10(-2) mbar. The P(O-2)/P-t partial pressu res ratio is changed from 0% to 20%. Investigations by X-ray diffracti on measurements (XRD), by infrared (IR), Raman and X-ray photoelectron (XPS) spectroscopies, by conductivity measurements and by optical tra nsmission spectroscopy are made in order to determine the structural, electrical and optical properties of V2O5 thin films. All the films gr own under oxygen partial pressure are identified as vanadium pentoxide . Their polycrystalline texture is such that the (001)-type planes lie parallel to the substrate. The average (001) interplanar spacing c is found to be greater than c(0) (value for bulk V2O5), and to increase with increasing sputtering gas O-2 content. The thermally induced redu ction under vacuum of V2O5 into a VO2 occurs at about 400 degrees C. O n the other hand, the treatment of electrical conductivity is made on the basis of Mott and Austin's theories. Finally, the optical constant s and thickness of the films are calculated using a simple and accurat e method based on the transmission spectrum alone and taking into acco unt thickness inhomogeneities in the sputtered films.