报告人单位(中文)：韩国釜山国立大学
报告时间：2015-04-24 09:45
报告地点：宝山校区东区材料学院801会议室

报告人简介(中文)：Park Chul Hong 教授 是韩国釜山国立大学介质新材料研究所的主任,主要研究领域为通过第一性原理计算研究铁电氧化物,半导体材料及磁性材料缺陷, 表面结构及宏观性能,已在Phys.Rev. Lett., Appl. Phys.Lett. 等刊物上发表论文60多篇. 
报告内容简介：Since ZnO-based oxide semiconductors are promising materials for transparent oxide electronics and blue LED, the oxides have been extensively investigated. The heavily n-type doping of ZnO is now intensively investigated for the application of the transparent conducting oxide for the solar cell. Hydrogen is an ubiquitous element, and in semiconductors, hydrogen-related problems have always been important subjects, since hydrogen shows complicated properties. Substitutional hydrogen at oxygen site (HO) is well-known to be a robust source of n-type conductivity in ZnO, but a puzzling aspect is that the doping limit by hydrogen is only about 1018 cm−3, even if solubility limit is much higher. There is another puzzling aspect in ZnO, which is persistent photo-conductivity (PPC) in Zn. Since the PPC is a source of the light-induced instability of ZnO-based active device in flat panel display, it prevents the wide applications of theZnO-based thin film transistor, andmany researches are now invested to prevent it, however up to now, there is no satisfactory theory about two puzzles. We report the bistability of HO in ZnO through first-principles electronic structure calculations. We find that as Fermi level is close to conduction bands, the HO can undergo a large lattice relaxation, through which a deep level can be induced, capturing electrons and the deep state can be transformed into shallow donor state by a photon absorption. We suggest that the bistability can give explanations to two puzzling aspects. Ref) H-H Nahm, C. H. Park, Y-S Kim - Scientific reports,4, 412 (2014)