近空间升华沉积CdTe多晶薄膜过程的研究

研究了近空间升华（CSS）沉积CdTe多晶薄膜的物理机制，测量了近空间沉积装置内的温度分布，分析了升温过程、气压与薄膜的初期成核的关系，优化了升温过程，在此基础上制备出了转换效率优良的结构为SnO2：F／CdS／CdTe／Au的串联集成太阳电池。同时结果表明：近空间升华制备TdTe多晶薄膜的物理过程主要是，Cd代升华前升温，Cd代源升华分解为Cd、Te2, Cd、Te2在衬底上化合沉积以及衬底上的CdTe反升华等过程。在正常的近空间升华过程中，CdTe的蒸汽压远小于保护气体的气压。后者对对成核的晶粒方向几乎没有影响，但它通过改变分子平均自由程来影响Cd、Te2分子的扩散，从而影响薄膜的生长速率。

Study on close-space sublimating and depositing process of CdTe Polycrystalline films' Preparation

The structure and characteristics of CdTe thin films are dependent on the whole deposition process in closed-space sublimation. It can be helpful to prepare the thin and compact CdTe thin films with fine photoelectric characteristics to study the heat exchange and mass transportation in CSS process. In this paper, the physical mechanism of CSS is analyzed, and the temperature distribution in CSS system is measured, and the dependence of preliminary nucleus creation on increasing-temperature process and pressure is studied. So the increasing-temperature curve has been optimized, the production of high-quality integrated cells with SnO_2:F/CdS/CdTe/Au structure are made possible. The results indicate: The physics process of the close space sublimation includes: the preliminary increasing-temperature process of the CdTe before sublimation. The process that CdTe source sublimates and decomposes into the Cd and the Te_2. The course of combining process of Cd, and the Te_2 on substrate, the course of CdTe resublimating on substrate. In the course of the normal close-spaced sublimation, CdTe vapor pressure is far smaller than the protecting atmosphere. The effect of the latter to grow nucleus is small. But it affects the growth velocity of the thin film from changing the molecular mean free path to affect the diffusion of Cd and Te_2.