Of V2o5 The Reduction Mechanism Of Vo2 Thin Films Prepared New Technology

The principle and mechanism of reduction of V₂O₅ was studied in detail by ESCA andXRD. The new approach of direct preparing the VO₂ thin films using V₂O₅, improving thespecial property of resistance of VO₂ thin films and lowering the phase temperature bydoping Mo were probed. The new technology of powder-coated method which was usedto prepare the VO₂ thin films was developed by using low vacuum degree N₂ flow tolower the oxygen partial pressure so as to reduce the V₂O₅ freezing layers under lowertemperature condition which were formed by the melting V₂O₅ powder.The study results show that the V₂O₅ melting is stable in air at lower temperature, butin higher temperature, it can be reduced and produce a little V⁴⁺. Lowering the oxygenpartial pressure of the system, the stability of V₂O₅ melting decreases, at the same time,the reduction reaction is stfengthened and the number of lower valence vanadium oxideincreases. The valence of the vanadium is controlled by the oxygen partial pressure and itsbalance condition in the system, i.e. the difference of oxygen partial pressure between themelting and the surrounding. By the very slow decrease of the oxygen pressure betweenthe meIting and the surrounding, the vanadium oxide, which is correspondence with theoxygen pressure, can be obtained. Or with the increase of the oxygen pressure differencebetween the melting and the surrounding, the valence of vanadium in the melting isdiscordance with the balance state, i.e. the valence is higher or lower than that in thebalance state.The special resistance property of VO₂ thin films is affected by many factors,including the purity of the VO₂, the thickness and the continuity of the thin films etc.Under the vacuum and higher temperature (l350℃), slowly lowering the oxygen pressurein the system, highly pure VO₂ deposit layer can be fOrmed directly by reducing V₂O₅melting. The magnitude of abrupt change of resistance for this deposit layer can reach upto 4--5, which exceeds obviously to other VO2 thin films obtained by other preparationmethods. For the thin film prepared by powder--coated method, its magnitude reaches uPto 3 --4, which is lower than that of highly pure VO2 deposit layer obtained by reducingVzOs melting under vacuum and higher temperature, but the requirement for preparingequiPment, condition and operation demand is lower than others.Doping Mo in the VO2 thin film can lower evidently the phase transition temper8ture,the decrease magnitUde is about l l'C/atm.%, but the special property of abruPt change ofresistance is lowered, too.