Semi-quantitative study on the Staebler-Wronski effect of hydrogenated amorphous silicon films prepared with HW-ECR-CVD system

The method of numerical simulation is used to fit the relationship between the photoconductivity in films and the illumination time. The generation and process rule of kinds of different charged defect states during illumination are revealed. It is found surprisingly that the initial photoconductivity determines directly the total account of photoconductivity degradation of sample.     

Light induced microstructure transformation in a-Si：H films

A series of a-Si：H films are deposited by hot wire assisted microwave electron cyclotron resonant chemical vapour deposition （HW-MWECR-CVD）, subsequently exposed under simulated illumination for three hours. This paper studies the microstructure change during illumination by Fourier Transformation Infrared （FTIR） spectra. There are two typical transformation tendencies of microstructure after illumination. It proposes a model of light induced structural change based on the experimental results. It is found that all samples follow the same mechanism during illumination, and intrinsic structure of samples affect the total H content.     

Nanomorph Silicon Thin Films Prepared by Using an HW-MWECR CVD System

We have prepared hydrogenated nano-amorph silicon (na-Si:H) films by using a hot-wire-assisted microwave electron-cyclotron-resonance (HW-MWECR) chemical vapour deposition (CVD) system. The films are deposited in two steps: in the first 9rain, a hydrogenated amorphous silicon layer is deposited by using hydrogen-diluted silane with a concentration of SiH4/(SiH4 H2) = 20%, and then a nanocrystalline silicon (nc-Si) layer is deposited by using various highly hydrogen-diluted silane. The Raman TO-like mode peak of the films was found in the range 497-508cm^-1. When the silane concentration used for preparation of the nc-Si layer is 14.3%, the film has a large crystalline volume fraction of 65.4%, a wide optical band gap of 1.89eV and a low hydrogen content of 9.5 at.%. Moreover, the na-Si:H films rather than nc-Si possess high photosensitivity of about 10^5.     

一种新型的可视化气体传感技术研究

光吸收气体传感技术由于具有与人类嗅觉细胞相似的巨量并行、交叉敏感及广谱响应特性,适用于承担电子鼻核心的气体传感任务~([1])。而常规的光栅光谱仪存在着光谱范围与分辨率相互制约的缺陷,因此本文提出将同时兼顾宽光谱、高分辨特性的空间外差光谱技术(SHS)~([2])应用于气体传感,构建出一种新型的基于光吸收和SHS的可视化气体传感技术(V-GST)。为了验证方案的可行性,文章首先构建可视化气体传感技术的系统模型,并搭建相应的实验平台,然后利用该平台对不同光源、不同浓度的NO_2进行检测。     

巧用折合质量求特殊简谐运动的周期

利用折合质量,求解几种不同类型的简谐运动问题.     

MWECR CVD等离子体系统梯度磁场对沉积a-Si:H薄膜特性研究

分别研究了磁场线圈电流为115.2和137.7A以及137.7A并在加热台下加放SmCo永磁体的方法，来改变单磁场线圈分散场MWECR CVD系统等离子体室及沉积室磁场形貌.用洛伦兹拟合定量地得到了三种磁场形貌的磁场梯度.研究了磁场梯度对沉积a-Si:H薄膜性能的影响.研究表明：在衬底附近，高的磁场梯度可以获得高的沉积速率；在温度不很高时，高的磁场梯度可得到光敏性较好的a-Si:H薄膜. 关键词： 梯度磁场 洛伦兹拟合 a-Si:H薄膜 MWECR CVD系统     

采用热丝辅助的新型微波电子回旋共振法制备高质量的氢化非晶硅薄膜

采用热丝辅助的新型微波电子回旋共振法制备了高质量的氢化非晶硅薄膜。在制备过程中，热丝对改进薄膜微结构，提高稳定性及光电特性方面起到了重要的作用。实验结果表明：在薄膜的微结构中，硅氢二键含量显著减少并出现了少量微晶相，其有利于改善薄膜的稳定性；在薄膜的光电特性方面，薄膜的沉积速率及光敏性分别达到了2.0nm/s和4.71*105以上。     

采用两步压强法制备优质微晶硅薄膜

针对氢化微晶硅薄膜吸收系数较低、制备需要较高厚度,从而需要较高沉积速度的问题,考虑到压强对沉积速度及晶化比的重要影响,在分析了单一压强法制备薄膜优缺点的基础上,提出了采用两步法来制备高质量微晶硅薄膜的方法。即先采用高压制备薄膜2m in,减小非晶转微晶的孵化层厚度,然后再采用低压制备薄膜18m in,提高薄膜的致密度及减小氧含量,最后制备出了光敏性较高,晶化比较大并且光照稳定性也较好的优质氢化微晶硅薄膜。     

巧借包络线方程 解斜抛中的极值问题

以3个例题为基础,讲解了借用包络线方程,解决斜抛中的极值问题.     

Preparation of hydrogenated microcrystalline silicon films with hot-wire-assisted MWECR-CVD system

Intrinsic hydrogenated microcrystalline silicon （μc-Si：H） films have been prepared by hot-wire-assisted microwave electron-cyclotron-resonance chemical vapour deposition （HW-MWECR-CVD） under different deposition conditions, Fourier-transform infrared spectra and Raman spectra were measured. Optical band gap was determined by Tauc plots, and experiments of photo-induced degradation were performed. It was observed that hydrogen dilution plays a more essential role than substrate temperature in microcrystalline transformation at low temperatures. Crystalline volume fraction and mean grain size in the films increase with the dilution ratio （R=H2/（H2＋SiH4））. With the rise of crystallinity in the films, the optical band gap tends to become narrower while the hydrogen content and photo-induced degradation decrease dramatically. The samples, were identified as μc-Si：H films, by calculating the optical band gap. It is considered that hydrogen dilution has an effect on reducing the crystallization activation energy of the material, which promotes the heterogeneous solid-state phase transition characterized by the Johnson-Mehl-Avrami （JMA） equation. The films with the needed structure can be prepared by balancing deposition and crystallization through controlling process parameters.