NSF-CGP Fellowship: Correlation of Stress with Hydrogen Microstructure and Photodegradation in Hydrogenated Amorphous Silicon

9802430该奖项为北卡罗来纳大学教堂山分校物理和天文学系韩大兴博士为期3个月的研究访问提供资金，以支持与日本岐阜市大学电气工程系西田昭二博士的合作。这两位合作者将研究氢化非晶硅(a-Si：H)中的光致应力变化及其与氢微结构和电子缺陷态密度的关系。这种a-Si：H材料是薄膜晶体管阵列的主要候选者，用于驱动大面积平板显示器，开发太阳能电池的清洁能源，以及大面积光传感器阵列。研究发现，传统的非氢稀释辉光放电本征材料具有很高的应力。这种材料表现出光降解，但它的稳定性能对于太阳能电池等大面积器件仍然相当好。然而，目前还不清楚这种应力是否与a-Si：H中的光致亚稳性有关，或者是否与a-Si：H中的氢微结构有关。最近的研究结果表明，通过在传统辉光放电过程中的氢稀释和热丝辅助的化学气相沉积技术，a-Si：H太阳电池的稳定性得到了显著的改善。岐福大学的研究小组最近开发了一种创新的工具，原子力显微镜，它利用弯曲光束方法对微弱的应力，如在薄石英上沉积的a-Si：H中的应力的光致变化非常敏感。这些更稳定的“新”非晶硅材料和创新工具为阐明a-Si：H中的应力和氢微结构以及电子性质之间的关系提供了一个独特的机会。所提出的研究将有助于深入了解亚稳态的微观结构来源，并加强关于这个非晶硅网络中结构和电子态之间关联的证据。该项目由国家科学基金会和日本基金会全球伙伴关系中心之间的科学奖学金计划资助。*

9802430HanThis award provides funds to support a 3-month research visit by Dr. Daxing Han, Department of Physics and Astronomy, University of North Carolina at Chapel Hill, for collaboration with Dr. Shoji Nitta, Department of Electrical Engineering, Gifu University, Japan. These two collaborators will investigate the photo-induced changes on stress and its correlation with hydrogen microstructure as well as the density of electronic defect states in hydrogenated amorphous silicon (a-Si:H). This material, a-Si:H, is a leading candidate for thin film transistor arrays to drive large-area flat panel displays and for the development of clean energy from solar cells, as well as for large-area photo-sensor arrays. It has been found that the conventional, non-hydrogen diluted glow discharge intrinsic material has very high stress. This material shows photo-degradation, but its stabilized properties are still quite good for large area devices such as solar cells. It has been unclear, however, whether the stress is correlated with the light-induced metastability, or whether there is a correlation of stress with hydrogen microstructures in a-Si:H. Recent results indicate that significant improvement in stability of a-Si:H solar cells has been made by hydrogen dilution during the conventional glow discharge and by the hot filament assisted chemical vapor deposition technique.The research group at Gifu University recently developed an innovative tool, the atomic-force-microscope, utilizing a bending-beam method, that is sensitive to weak stress such as the light-induced changes of the stress in a-Si:H deposited on thin quartz. These more stable "new" amorphous-silicon materials and the innovative tool offer a unique opportunity to elucidate the correlation between the stress and hydrogen microstructure as well as the electronic properties in a-Si:H. The proposed investigations will help provide an insight into the microstructure origin of the metastability and enhance the evidence for the correlation between structural and electronic states in this amorphous silicon network. This project is supported under the Science Fellowship Program between the National Science Foundation and the Japan Foundation Center for Global Partnership.***