W掺杂VO_2薄膜的椭圆偏振光谱表征

Spectroscopic Ellipsometry Characterization of Tungsten-doped Vanadium Oxide Films

利用MSP-3200三靶共溅射镀膜机,射频磁控溅射在石英基底上反应溅射制备单斜相（M相）VO_2薄膜及W掺杂单斜相（M相）VO_2薄膜。利用WVASE32椭圆偏振仪及变温附件在350~2 500 nm波长范围内对相变前后的VO_2薄膜及W掺杂VO_2薄膜进行光谱测试,运用Lorentz谐振子色散模型结合有效介质近似模型对椭偏参数进行拟合。结果表明：W掺杂的VO_2薄膜与纯相的VO_2薄膜相比,光学常数n、k随波长的变化趋势相同,但W掺杂后的VO_2薄膜的折射率n小于纯相VO_2薄膜的折射率,而消光系数k值大于纯相VO_2薄膜的k值。W的掺入增加了薄膜的致密度,同时增加了薄膜内部自由载流子的浓度。

The monoclinic phase （M phase） WO2 film and W-doped M phase VO2 film were prepared on quartz substrate by a model MSP-3200 three targets co-sputter coater with RF magnetron reactive sputtering. The optical properties in the wavelength range of 350-2500 nm of VO2 film and W-doped VO2 film were investigated by spectroscopic ellipsometry with variable temperature attachment. The ellipsometric parameters φ and A were fitted by the Lorentz harmonic oscillator dispersion model combining with effective medium approximation model. The results show that the optical constants n, k of W-doped VO2 film vary with wavelength, compared to pure phase VO2 film, and the refractive index n of the W-doped VO2 film is less than that of the pure phase VO2 film. However, the extinction coefficient k of W-doped VO2 film is greater than that of pure phase VO2 film. The doping of W increases both the packing density and concentration of free carriers in VO2 film.