采用CdTe和Te双源共蒸发的方法,调控CdTe和Te源的蒸发速率,首次制备出一系列不同x组分的CdxTe二元化合物薄膜,并在N2气气氛下进行185℃退火处理。通过XRD、SEM、紫外–可见吸收光谱分析及暗电导率–温度关系对CdxTe薄膜的结构、形貌、光学和电学性质进行表征。紫外–可见吸收光谱分析表明,不同x组分的CdxTe薄膜,其禁带宽度可在0.99~1.46 eV之间变化,随着x值从0.8减小到0.2,吸收边向长波方向移动,而且透过率也显著下降。XRD结果表明, x值小于0.6时,刚沉积的CdxTe薄膜为非晶相；随着x的值逐渐靠近1,刚沉积的薄膜明显结晶,沿CdTe(111)方向择优生长,退火处理促使薄膜从非晶转变为多晶。CdxTe薄膜的导电类型为p型,其暗电导率随温度的上升而增大,当温度继续升高至临界点时,薄膜暗电导率–温度关系出现反常。这些结果表明, CdxTe薄膜将有望用于CdTe薄膜太阳电池以拓展电池的长波光谱响应。
CdxTe thin films with differentx values were deposited for the first time through controlling evaporation rates of CdTe and Te powder by vacuum co-evaporation. Then the films were annealed in N2atmosphere at 185℃. The morphological, structural, optical, and electrical properties of the CdxTe films were investigated by X ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible absorption spectrum and temperature dependence of the dark conductivity. UV-visible absorption spectrum demonstrates that energy band gaps (Eg) of different CdxTe films change from 0.99 eV to 1.46 eV. The absorption edges of different CdxTe films move towards longer wavelength and their transmittances reduce dramatically as thex value decreases from 0.8 to 0.2. XRD shows that as-deposited CdxTe thin films are amorphous when value ofx is less than 0.6. Otherwise, CdxTe thin films are crystalline whose CdTe phase with preferential in (111) direction while value ofx is approaching 1. The result indicates that annealing treatment is helpful for the films shifting from amorphous to polycrystalline. All the films exhibit p-type conductivity and the con-ductivity increases firstly as temperature rises. But it becomes abnormal while the temperature reaches a certain point. Data from this research suggest that CdxTe thin films can potentially be used for CdTe thin film solar cells to improve the long wavelength response.
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