CdSyTe1-y多晶薄膜的制备及光谱表征

采用真空共蒸发法制备了CdSyTe1-y(0≤y≤1)多晶薄膜,并用X射线衍射谱(XRD)、能量色散谱(EDS)研究了CdSyTe1-y多晶薄膜的结构、组分。实验结果表明:石英振荡法监控的组分与EDS谱结果较为一致;当y<0·3时,CdSyTe1-y多晶薄膜为立方结构,当y≥0·3时,CdSyTe1-y多晶薄膜为六方结构。采用XRD线形分析法可计算出CdSyTe1-y多晶薄膜晶粒大小约20～50nm。最后,用紫外-可见-近红外谱(UV-Vis-NIR),测得300～2500nmCdSyTe1-y多晶薄膜的透过率曲线,并结合一阶Sellmeier模型的折射率色散关系,表征了CdSyTe1-y多晶薄膜的光学性质,获得了CdS0·22Te0·78多晶薄膜的光学厚度d～535nm,光能隙Eg～1·41eV,以及吸收系数α(λ)、折射率n(λ)等光学量。结果也表明,采用真空共蒸发法可以制备需要组分的CdSyTe1-y多晶薄膜,对CdSyTe1-y多晶薄膜光学性质的表征方法可推广到其他的半导体薄膜材料。

Preparation and Spectral Characterization of CdSyTe1-y,Thin Films

CdS(y)Te(1-y) (0 < or = y < or = 1) polycrystalline thin films were prepared on glass substrates by co-evaporation of powders of CdTe and CdS. For the characterization of the structure and composition of the CdS(y)Te(1-y) thin films the X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) were used. The results indicate that the values of sulfur content y detected and controlled by the quartz wafer detector show good agreement with the EDS results. The films were found to be cubic for x < 0. 3, and hexagonal for x > or = 0.3. The 20-50 nm of grain sizes for CdS(y)Te(1-y) thin films were calculated using a method of XRD analysis. Finally, the optical properties of CdS(y)Te(1-y) thin films were characterized by UV-Vis-NIR spectroscopy alone. According to a method from Swanepoel, together with the first-order Sellmeier model, the thickness, of d-535 nm, energy gap of E(g)-1.41 eV, absorption coefficient, alpha(lambda) and refractive index, n(lambda) of CdS(0.22) Te(0.78) thin films were determined from the transmittance at normal incidence of light in the wavelength range 300-2 500 nm. The results also indicate that the CdS(y)Te(1-y) thin films with any composition (0 < or = y < or = 1) can be prepared by co-evaporation, and the method to characterize the optical properties of CdS(y)Te(1-y) thin films can be implemented for other semiconductor thin films.