ZnSe/SiO_2复合薄膜光学常数与荧光光谱的研究

Luminescence and optical constant of ZnSe/SiO_2composite thin films

采用溶胶-凝胶工艺与原位生长技术,制备了ZnSe/SiO_2复合薄膜.X射线衍射分析表明薄膜中ZnSe晶体呈立方闪锌矿结构.X射线荧光分析结果显示薄膜中Zn与Se摩尔比为1∶1·01—1∶1·19.利用场发射扫描电子显微镜观察了复合薄膜的表面形貌,结果表明复合薄膜表面既存在尺寸约为400nm的ZnSe晶粒,也存在尺寸小于100nm的nSe晶粒.利用椭偏仪测量了薄膜椭偏角Ψ,Δ与波长λ的关系,采用Maxwell-Garnett有效介质理论对薄膜的光学常数、厚度、气孔率、ZnSe的浓度进行了数据拟合.利用荧光光谱分析了薄膜的光致发光,结果表明在波长为395nm的激发光下,487nm的发射峰对应着闪锌矿型ZnSe的带边发射,同时也观测到薄膜中ZnSe晶体增强的自由激子发射及伴随着ZnSe晶体缺陷而产生的辐射发光.

The ZnSe/SiO2 composite thin fihns were prepared by sol-gel process and in-situ growth technique. X-ray diffraction results showed that the phase structure of ZnSe particles embedded in ZnSe/SiO2 composite thin films is the sphalerite （cubic ZnS）. X-ray fluorescence results revealed that the molar ratio of Zn/Se is about 1 ： 1.01-1 ： 1.19. Scanning electron microscopy results revealed that the size of ZnSe crystal particles is about 400 nm, while some particles are less than 100 nm in size. The dependence of ellipsometric angle Ψ, Δ with wavelength λ of ZnSe/SiO2 composite thin films was investigated with spectroscopic ellipsometers. The optical constant, thickness, porosity and the concentration of ZnSe in ZnSe/SiO2 composite thin films were fitted according to Maxwell-Garnett effective medium theory. The photoluminescence properties of ZnSe/SiO2 composite thin films were inw.stigated with fluorescence spectrometer. The photoluminescence results indicated that the emission peak at 487 nm under 395 nm excitation corresponds to the band-to-band emission of sphalerite ZnSe crystal. The strong free exciton emission and other emission peaks correlated with ZnSe lattice defect were also observed.