Huang Wanxia

Study on Phase Transition Property of Tungsten-doped Vanadium Dioxide Thin Film at Terahertz Range

Vanadium dioxide and tungsten-doped (W-doped) vanadium dioxide thin films deposited by aqueous Sol-Gel method were characterized with several different techniques (i.e. X-ray photoelectron spectroscope, atomic force microscope, X-ray diffraction), to determine their morphology and microstructure. Their metal-to-insulator (MIT) phase transition behavior in infrared spectral region (λ=4 μm) and terahertz (THz) spectral region (0.3–1.0 THz) were observed respectivele. The results demonstrate that the transmittance of W-doped VO 2 film at room temperature is visibly lower than that of undoped VO 2 film in both infrared and terahertz spectral region. The transition temperature of W-doped VO 2 film is also lower than that of undoped VO 2 film in the THz range. The MIT and structural phase transition (SPT) are observed during the phase transition of VO 2 and W-doped VO 2 , and an obvious change of peak position occurs in W-doped VO 2 film.

Study on shielding functionally gradient materials with low reflection loss and high absorption loss for electromagnetic wave

In this paper, the double gradient model for shielding functionally gradient materials (SFGMs) with low reflection loss and high absorption loss in less than 1 GHz is put forward to reduce pollution of the electromagnetic wave. In SFGMs, double impedance matching layers on the surface and high absorption layer in center and double impedance transition layers between the surface and center are designed. The based on nickel and (Ni,Zn)Fe/sub 2/O/sub 4/ gradient composite shielding coatings are prepared. The test results of the coatings showed that, the reflection loss was decreased 6/spl sim/8 dB and the absorption loss was increased 6/spl sim/14 dB.

Optical Switching and Color Changing Properties of VO2 Films on Muscovite Substrate

Abstract VO2 films on muscovite substrate were fabricated by inorganic sol-gel method and the following thermal treatment. The films were characterized by X-ray diffraction, scanning electron microscope (SEM), fourier transform infrared spectrophotometer (FTIR) and color difference (ΔE*). The FTIR result shows that the film has an infrared transmittance switching efficiency of 77% in the metal-insulator transition. The color changing properties indicate that the film color reversibly changes from khaki to yellow-green as the temperature changes. The relationship between ΔE* and the temperature presents a hysteresis loop, which is in accordance with the infrared optical switching properties. The maximum of ΔE* during the film metal-insulator transition is 11.31.

W-Mo复合离子掺杂VO 2 薄膜热滞回线的热调制现象

以单晶Si (100)为基底, 采用无机溶胶–凝胶法在其表面制备W-Mo复合离子掺杂VO 2 薄膜。采用SEM、XRD等手段分析了薄膜的表面形貌和晶体结构。在热驱动下, 利用原位FTIR分析了W-Mo复合离子掺杂VO 2 薄膜半导体–金属相变性能。结果显示: 单晶Si (100)表面VO 2 薄膜具有(011)择优生长取向, W 6+ 、Mo 6+ 取代了V 4+ 在晶格中的位置, 实现置换掺杂。热滞回线分析表明, 与未掺杂VO 2 薄膜相比, V 1- x - y Mo x W y O 2 薄膜相变温度降低, 滞后温宽减小, 同时相变陡然性变差, 相变温宽增大; 在相变温度区间内, 温度路径对红外透过率具有调制效果, 其调制作用受原始热滞回线的制约。以单晶Si (100)为基底, 采用无机溶胶–凝胶法在其表面制备W-Mo复合离子掺杂VO 2 薄膜。采用SEM、XRD等手段分析了薄膜的表面形貌和晶体结构。在热驱动下, 利用原位FTIR分析了W-Mo复合离子掺杂VO 2 薄膜半导体–金属相变性能。结果显示: 单晶Si (100)表面VO 2 薄膜具有(011)择优生长取向, W 6+ 、Mo 6+ 取代了V 4+ 在晶格中的位置, 实现置换掺杂。热滞回线分析表明, 与未掺杂VO 2 薄膜相比, V 1- x - y Mo x W y O 2 薄膜相变温度降低, 滞后温宽减小, 同时相变陡然性变差, 相变温宽增大; 在相变温度区间内, 温度路径对红外透过率具有调制效果, 其调制作用受原始热滞回线的制约。

TiO 2 中间层对基于溶胶–凝胶法制备的VO 2 薄膜光学特性的影响

为了提高VO 2 薄膜的热致相变性能, 采用复合结构与掺杂相结合的方法, 首先通过溶胶-凝胶法在云母基底上制备锐钛型TiO 2 薄膜, 再在光致亲水性处理的TiO 2 /云母基底上涂覆V 2 O 5 以及掺钨V 2 O 5 水溶胶, 然后经热处理获得VO 2 /TiO 2 及V x W 1- x O 2 /TiO 2 复合薄膜. 采用X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、傅立叶变换红外光谱仪(FTIR)研究薄膜的物相, 表面形貌以及热致相变特性. 结果表明, VO 2 /TiO 2 复合薄膜晶体生长为(011)面择优取向; V x W 1- x O 2 /TiO 2 复合薄膜产生多种取向. TiO 2 中间层有助于使VO 2 薄膜生长致密, 相变温度降低, 更使V x W 1- x O 2 /TiO 2 复合薄膜滞后温宽降至约4℃.为了提高VO 2 薄膜的热致相变性能, 采用复合结构与掺杂相结合的方法, 首先通过溶胶–凝胶法在云母基底上制备锐钛型TiO 2 薄膜, 再在光致亲水性处理的TiO 2 /云母基底上涂覆V 2 O 5 以及掺钨V 2 O 5 水溶胶, 然后经热处理获得VO 2 /TiO 2 及V x W 1- x O 2 /TiO 2 复合薄膜。采用X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、傅立叶变换红外光谱仪(FTIR)研究薄膜的物相、表面形貌以及热致相变特性. 结果表明, VO 2 /TiO 2 复合薄膜晶体生长为(011)面择优取向; V x W 1- x O 2 /TiO 2 复合薄膜产生多种取向。TiO 2 中间层有助于使VO 2 薄膜生长致密, 相变温度降低, 更使V x W 1- x O 2 /TiO 2 复合薄膜滞后温宽降至约4℃。