| Vanadium dioxide(VO2) is a solid-state material, when the temperature rises to68℃the reversible transformation from non-metal phase to metal phase will happen. VO2phase transition is accompanied by reversible mutation of the material's resistance, magnetic susceptibility, and light transmittance. The phase transition temperature can be lowered to near room temperature by doping, therefore, VO2is widely applied in many fields. On one hand, VO2and other semiconductor materials can be used to prepare heterojunction, photoelectric detectors, photovoltaic cells and other optoelectronic devices; the other hand, the direct preparation of VO2thin films on the substrate can be applied to the development of the smart glass and laser protective devices. The key of large-scale application of VO2thin films is how to reduce the phase transition temperature to room temperature and without the influence on the mutation amplitude of the optical and electrical properties. Among several methods, doping is an effective method. Base on the former experience on the issue and related literature, we mainly study on the optical and electrical properties of VO2thin films which is doped by the mean of nanoclusters in this paper.The doping of VO2thin film is achieved by preparing nanoclusters structure, which take advantage of the way of surface tension self-assembling in nanospheres lithography. And then we use RF magnetron sputtering technique for thin film deposition. By those procedures, we prepared two kinds VO2film containing nanoclusters structure, one of them is not doped, the other is doped by Pt. In this paper, the optimized condition for preparing VO2films is summarized, and the optical-electrical properties of those films are the focus of my research.Studies have shown that the resistance mutation rate of non-doped VO2thin films containing nanoclusters structure can reach81.8%, the mutation rate of optical transmission is able to be15%at wavelength of1100nm, the phase transition temperature is between56-72℃. At the same time, the resistance mutation rate of VO2thin films Pt nanoclusters doping is up to66.7%, the mutation rate of optical transmission can reach7%at wavelength of1100nm, the phase transition temperature is between38-58℃. Comparing with the conventional VO2thin films, whose resistance mutation rate is72.7%, optical transmittance mutations is9%at wavelength of1100nm, the phase transition temperature is58-74℃, we can conclude that the impact on the optical properties of VO2thin films with pure nanoclusters doping is more obvious (the magnitude of optical transmittance mutation at wavelength of1100nm increase6%), and by Pt clusters doping the phase transition temperature of VO2film can be significantly reduced (the decline is nearly20℃). Through the study on the optical and electrical properties of VO2thin films doped by nanoclusters, we can realize its potential on the applications in the smart glass, photoelectric switches and solar temperature materials, and so on.Moreover, considering that the VO2-related heteroj unction has not been extensively carried out currently, we prepared VO2/Nb:SrTiO3heterojunction in niobium-doped(wt.0.7%) strontium titanate doped substrate and study its electrical properties for extending the realm of the application of the VO2. We tested the currentvoltage characteristics of VO2/Nb:SrTiO3heterojunction under low and high temperature respectively, both of those showed good rectifying behavior. By analysis, we believe that the VO2has phase transition properties, so under low temperature the VO2/Nb:SrTiO3heteroj unction will be n-N heterojunction, and under high temperature it will be the Schottky junction. In the measurements, we also observed the hysteresis phenomenon of VO2/Nb:SrTiO3heterojunction, which is due to the carrier bound-off the bound mechanism on the interface of the heterojunction. In addition, the article also measured the photovoltaic effect of VO2/Nb:SrTiO3heterojunction, it is found that the sample can produce the photovoltaic effect when it is irradiated by the laser whose wavelength is248nm, energy is1.1mJ, and maximum open circuit voltage is about3.5mV. Through the exploration of the electrical properties of the VO2/Nb:SrTiO3heterojunction, we can believe that the heterojunction can be applied in the fields of photodiodes, photovoltaic cells and photodetectors. |
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