ZnSe/SiO_2薄膜光学常数的椭偏光谱测量

The Optical Constant of ZnSe/SiO_2 Thin Film Investigated by Spectroscopic Ellipometry

采用溶胶-凝胶工艺与原位生长技术,制备了ZnSe/SiO2复合薄膜。X-射线衍射(XRD)分析表明,ZnSe/SiO2复合薄膜中ZnSe晶体为闪锌矿(立方ZnS)。利用椭偏光谱仪测量了不同ZnSe含量的ZnSe/SiO2复合薄膜的椭偏参数Δ与波长λ的色散关系,采用Maxwell-Garnett(MG)有效介质理论对薄膜的光学常数、厚度、气孔率、ZnSe的浓度进行了计算。结果表明,单层ZnSe/SiO2薄膜厚度在300 nm以上时,随着溶胶体系Zn2+、SeO42-浓度的增加而增大,气孔率在30%左右,ZnSe含量约为溶胶体系中Zn2+、SeO42-浓度的1/2;通过MG有效介质理论的计算表明,可以通过调整旋涂次数及Zn2+、SeO42-浓度来调整薄膜的厚度和ZnSe/SiO2的摩尔比率,可在工艺上控制ZnSe/SiO2复合薄膜光学参数。

The ZnSe/SiO2 composite thin films were prepared by Sol-Gel process and in-situ growth technique under carbon monoxide condition. XRD analysis reveals that the structure of ZnSe phase is sphalerite （cubic ZnS）. Spectroscopic Ellipsometers has been used to investigate the dependence of Ellipsometric angle Δ with wavelength λ The optical constant , thickness, porosity and the concentration of ZnSe of ZnSe/SiO2 composite thin films have been calculated according to maxwell-garnett（MG）effective medium theory. The fitting results shown that the thickness , the porosity and the molar ratio of ZnSe/SiO2 are over 300nm, 30%（V/V）, 1/2 of the molar ratio of Zn^2＋ / TEOS in original solution , respectively. The thickness increases with the increases of Zn^2＋ ,SeO4^2- concentration in solution. All calculated results revealed that we can adjust the thickness and the molar ratio of ZnSe/SiO2 through adjusting spin-coating times and the concentration of Zn^2＋ ,SeO4^2- in solution, which is valuable to control the optical properties of ZnSe/SiO2 composite thin films.