New method for preparing VO₂ films

The principal methods for preparing VO₂ films are: reactive sputtering, reactive evaporation, MOCVD and sol-gel methods. All these four methods have a common defect: high starting material cost. To overcome this defect is the purpose of this paper. The starting material currently used by sol-gel method is vanadium alkoxide. The authors' opinion is that several vanadium oxides can also be used as starting material. There also exist many methods for making sol from vanadium oxides. After much exploration and testing, the authors accomplished two unseparably connected things: (1) one kind of vanadium oxide is found to be satisfactory for the authors' purpose; (2) one method of preparing sol is found to be satisfactory for the authors' purpose. Starting from this sol and employing the well known dip-coating process, the authors succeeded in preparing a vanadium oxide film that possesses reversible phase transition property. Such a film exhibits typical VO₂ properties, among which electrical properties are comparable to those of similar films prepared in well-equipped laboratories in the world. The authors studied preliminarily the chemical composition and electrical properties of the film prepared by them. The results of analysis of ESCA of the film show that in such a film VO₂ is about 60%, and the rest includes several kinds of lower-valence vanadium oxides. The electrical resistance switching of the film is demonstrated. Around 60°C an abrupt drop of electrical resistance by two to three orders of magnitude is achieved.