对纳米硅薄膜高电导机制的探讨

使用超高真空PECVD薄膜沉积系统制备的纳米桂薄膜（nc－Si：H）具有高电导特性。为了探讨其导电机制，先使用K．Yoshida早期提出的两相无序结构有效电导模型分别对晶粒电导和界面电导进行了理论计算。指出，nc－Si：H股中高电导主要来自于细微晶粒的传导，界面可视之为非导体。另一方面，实验证实nc－Si：H股的电导率随平均品粒尺寸减少而增大，具有明显的小尺寸效应。文中首次提出，nc－Si：H膜的微晶粒具有异质结量子点（HQD）特性，并按此模型对nc－Si：H膜的电导率实验曲线进行了讨论。理论与实验结果符合得很好．又得出，硅薄膜结构在其晶态体积百分比Xc=0．30和0．70处呈现出两个明显的相变点。

An Exploratory Study of the Conduction Mechanism of Hydrogenated Nano-crystalline Silicon Films

Hydrogenated nano-crystalline silicon (nc-Si: H ) films are prepared by using ultra-high vaccum plasma enhanced chemical vapor deposition system. The experimental results show that conductivity of the nc-Si: H films in-creases with decrease of the mean grain-size of the films. There exists evident small size effect on the conduction process. Based on the experimental data, the effective-medium theory is used to calculate the partical conductivities ffe of crystallites and δi of interface. From the calculation, it is found that there exist two structure phase change points in the materials. The results suggest that the high conductivity of nc-Si: H films results mainly from the crystallites and the interface region may serve as insulator layers. Thus, it is considered that the crystallites in the nc-Si: H films act as quantum dots. A heteroquantum dots tunneling model is presented in this pa-per to discuss the transport process of the nc-Si: H films. The calculated results agree very well with the experimental conductivity data of the nc-Si: H films-