Preparation Of Vanadium Oxide Thin Films And Study Of Optical Properties

As the natural resources are increasingly deficient nowadays,people start to establish environmental awareness.The effective use of solar energy has become one of the hot spots in the current research.Discovery of the Metal-Insulator Transition property of VO₂ has created an opportunity for the development of Smart Windows,which can use of solar energy effectively to regulate indoor temperature.It has a high transmittance at low temperatures and a high reflectance at high temperatures.But it's hard to apply VO₂ thin films to the window glass,as vanadium-oxide systems are complex.There are as much as 13 compounds with different structures.Preparation of a single phase of VO₂ is not easy.A popular approach to get VO₂ thin films is to get a single phase of V₂O₅ firstly,Annealing treatment of the product under an optimized condition.Therefore,it is very significant to study the pure phase of V₂O₅.In this thesis,a variety of vanadium oxide thin films were prepared by DC magnetron sputtering and RF magnetron sputtering,respectively adopted high purity vanadium metal target and V₂O₅ Ceramic target.Effects of annealing conditions on the properties of the films were studied.The main contents of this Paper and the research results obtained are as follows:Firstly,V₂O₅ thin films were prepared on ordinary glass substrates by DC magnetron sputtering.The influence of vanadium oxide thin film structure to the argon oxygen ratio,sputtering power,substrate temperature and sputtering time were studied.XRD results show that all samples were pure phase V₂O₅.There is no other vanadium oxide phase.A series of experiments were carried to test the transmittance of V₂O₅ films and the results were analyzed.By comparison,the best technological Parameters of pure V₂O₅ thin film with high transmittance are: substrate temperature 250?,sputtering power 190 W,sputtering time 10 min,oxygen-argon ratio 5: 60.Then we studied the effect of vacuum annealing on the composition of the film,XRD Patterns,Raman spectroscopy and infrared transmittance of the annealed films were tested.The results show that vacuum annealing will reduce internal defects in the thin film transistor,thereby improve the crystallinity effectively.Finally,we use hydrogen to reduction of vanadium pentoxide thin films at 450? in a tube furnace.Based on the XRD Patterns of the samples,V₂O₃ were prepared,which is the product of over reduction.Secondly,Preparations of vanadium oxide thin films by RF magnetron sputtering,V₂O₅ ceramic target as a target.The vanadium oxide thin films prepared by this method are amorphous structure.We have different conditions for the heat treatment of the amorphous structure of thin film samples.Vanadium oxides with Different Valence States appeared in vacuum annealing,the main products were V₂O₃.The resulting vanadium oxide is more complex by annealing reduction under a hydrogen atmosphere.Then we tested the IR transmittance under different temperature.The results showed that,the infrared transmittance between 60? and 70? was changed significantly.Thus,we speculate that the significant change of IR transmittance between 60? and 70? is caused by a phase transition of VO₂ in the product.