摘要:
过渡金属氧化物二氧化钒(VO2)在温度340 K附近会发生金属绝缘体的转变(metal-insulator transition, MIT).基于金属绝缘体的转变性质, VO2薄膜材料具有很好的应用前景.本文首先采用脉冲激光沉积制备了高质量的V2O5薄膜,再通过高温氢退火还原V2O5薄膜制备出VO2多晶薄膜.研究了不同的退火温度、退火时间、退火气氛对VO2薄膜制备的影响,采用X射线衍射、X射线光电子能谱、变温电阻特性测量等手段对样品进行分析,发现在H2(5%)/Ar退火气氛下,在一定的退火温度范围内(500-525?C),退火3 h,得到了B相和M相共存的VO2薄膜,具有M相的VO2的MIT特性,而相同退火温度下退火时间达到4.5 h,薄膜完全变成B相的VO2.通过纯Ar气氛下对B相VO2再退火,得到了转变温度为350 K,电阻突变接近4个数量级的M相的VO2薄膜.实现了VO2的B相和M相的相互转变.
Abstract:
Owning to its sharp metal-insulator transition at～340 K, VO2 is becoming an attractive candidate for the electrical and optical material. Here we report on the fabrication and characterization of VO2 thin film obtained from the V2O5 thin film annealed in Ar/H2 ambience. V2O5 thin film is fabricated by using the pulsed laser deposition system on the R-sapphire substrate under several different conditions by varying the substrate temperature and the pressure of the growth atmosphere to optimize the growth condition. Then we carry out the annealing treatment on the V2O5 thin film in different annealing conditions. The VO2 thin films are characterized using X-ray diffraction, X-ray photoelectron spectroscopy and R-T measurement. When annealed in a temperature range of 500-525 ?C for 3 h in H2(5%)/Ar ambience, the V2O5 thin film can be converted into the mixed-structures of metastable monoclinic structure (B) and the monoclinic rutile structure (M) which is responsible for the phase-change property. And under the same conditions, when the annealing time reaches 4.5 h, the pure VO2(B) is obtained. Further we anneal the VO2(B) in pure Ar ambience and tentatively realize the resistivity reduced by nearly four orders with the temperature increasing from 25?C to 105?C. The transition temperature is nearly 350 K. And the transition between VO2 (B) and VO2 (M) is realized.
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