真空度对VO_2(B)型薄膜制备及光电特性的影响

Effect of Vacuum on Preparation and Optical and Electrical Properties of VO_2(B) Film

对不同真空度下得到的VO2（B）型薄膜的结晶状况、组分、电学性质和光学性质进行测试和分析，以探讨退火真空度对VO2（B）型薄膜的影响。以高纯五氧化二钒（V2O5）粉末（纯度高于99．99％，质量分数）为原料，采用真空蒸发——还原工艺，分别在高、低真空度下还原出VO2（B）型（空间群为C2/m）薄膜。利用X射线衍射（XRD）仪，X射线光电子能谱仪（XPS），电阻温度关系（TCR）测试仪和紫外可见分光光度计对薄膜进行测试，讨论了退火真空度对VO2（B）型薄膜的结晶状况、组分、电学性质和光学性质的影响。结果显示，在高、低真空度下退火，VO2（B）型薄膜出现的温度范围是不同的，在低真空度下退火出现的范围在400～480℃，而在高真空度下退火出现的范围只有400～440℃；高真空度退火得到薄膜的晶粒较大，透过率较低真空度得到的薄膜高7％～8％；但在低真空度下退火，薄膜中的V更易被还原，电阻温度系数绝对值更大，最大可达-2．4％／K。

The structure, valence, electrical properties and optical properties of the VO2 （B） thin films are analysed and measured to study the effect of annealing vacuum on the thin films. The VO2 thin films are deposited by vacuum-evaporation technology using the V2O5 powder （purity≥99.99%, in mass） as raw material. The V2O5 thin films are annealed at high and low vacuum in the vacuum coating machine, respectively. The space group of the obtained VO2 （B） thin films is C2/m. The thin films are measured by X-ray diffraction （XRD）, X-ray photo-electron spectrum （XPS）, temperature coefficient resistance （TCR） instrument and ultraviolet-vlsible spectrophotometer. The results suggest that the temperature range of the VO2 （B） thin films gained is different. The range is from 400 ℃ to 480 ℃ when the film is annealed in low vacuum, and it was only from 400 ℃ to 440 ℃ when the film is annealed in high vacuum. The crystal sizes change bigger and the transmission of the thin films annealed in the high vacuum is 7%-8% bigger than that annealed in low vacuum, but the vanadium＇s valence of the thin films are lower and the TCR＇s absolute value of the films are bigger which is up to -2.4%/K when annealed in low vacuum.