Growth and physical properties of vanadium oxide thin films with controllable phases
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Growth and physical properties of vanadium oxide thin films with controllable phases Yanda Ji1, Yin Zhang1, Min Gao1, Zhen Yuan2, Changqing Jin2, Yuan Lin1* 1. State Key Laboratory of Electronic Thin films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, P. R. China 2. The Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, P. R. China
ABSTRACT Vanadium oxides thin films with variable oxidation states have attracted great attention due to their unique electrical, optical properties and many important applications in microelectronics, infrared optical devices, and energy harvest systems. However, to fabricate vanadium oxide thin films with controllable phases and desired transport properties is still a challenge by using a chemical solution deposition (CSD) technique. In this paper, we report that vanadium oxide thin films with well controlled phases such as rhombohedral V2O3 and monoclinic VO2 could be synthesized on Al2O3 (0001) substrates using a CSD technique ---- polymer assisted deposition (PAD). Both V2O3 and VO2 thin films can be well controlled with good epitaxial quality by optimizing the fabrication parameters. The electrical resistivity changes 3~4 orders of magnitude at metal insulator transition for both epitaxial V2O3 and VO2 thin films. The correlation between the physical properties and the microstructures of the films will be discussed. INTRODUCTION The vanadium element exhibits different chemical valences in the family of vanadium oxides including V2O3, VO2 and V2O5 etc. V2O3 is always considered to be a typical Mott insulator and undergoes Mott metal insulator transition (MIT) above the liquid nitrogen temperature [1].This unique property makes V2O3 to be a great candidate to investigate the theory of Mott transition mechanism. However, there is few report on the device applications based on V2O3 due to its low transition temperature at around 155 K. Fortunately, VO2 exhibits the MIT property at just above room temperature. Under this temperature, many feasible devices applications in microelectronics, infrared optical devices, and energy harvest systems can been developed [2-4]. In fact, the structure of VO2 changes from a monoclinic, called M1 phase, to a rutile structure with the intermediate monoclinic M2 phase [5]. As a result, the metal insulator transition mechanism is under a controversy of Peierls or Mott mechanisms [6]. Because of difficulties in controlling the multiple chemical valences of vanadium, it is still a challenge to deposit vanadium oxide thin films with controllable phases and desired transport properties, especially by using a low-cost and manufacturable way. Compared to other thin film deposition techniques, chemical solution deposition (CSD) techniques show advantages of low
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cost, easy setup and ability for large area coating. Polymer assisted deposition (PAD) is an effective chemical solution deposition technique for the fabrication of functional oxide thin films [7]. In thi
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