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学术报告通知应信息光子学与光通信国家重点实验室/信息光子学与光通信研究院邀请，美国凯斯西储大学杨山博士于2014年9月17日访问我校并作学术报告。欢迎师生踊跃参加。报告题目：光学材料的点缺陷研究 Detection of Point Defects in Optical Materials 时间：2014年9月17日（星期三）上午9:00-10:00地点：新科研楼314会议室 Abstract: Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to identify and characterize point defects in TiO2 crystals having the rutile structure. Spectra with S = 1/2 and S = 1 are assigned to singly ionized and neutral oxygen vacancies, respectively. A Ti3+ ion next to a substitutional Si4+ ion, a Ti3+ self-trapped electron, and a self-trapped hole on the oxygen sublattice are also observed. Fluorine ions substitute for oxygen and are present as unintentional impurities in TiO2 crystals. Isolated singly ionized fluorine donors in an as-grown (fully oxidized) crystal convert to their neutral charge state during exposure to 442 nm laser light at 6 K. These donors return to the singly ionized charge state within a few seconds when the light is removed. In contrast, the neutral fluorine donors are observed at 6 K without photoexcitation after a crystal is reduced at 600 ºC in flowing nitrogen gas. The unpaired electron is localized primarily on one of the two equivalent neighboring substitutional titanium ions, i.e., the ground state of the neutral fluorine donor in rutile-structured TiO2 is a Ti3+ ion adjacent to a F- ion. Hydrogen, in the form of an OH- ion, is a shallow donor in TiO2. In the neutral charge state, the unpaired electron forms an adjacent Ti3+ ion. The hydrogen EPR signal cannot be produced in oxidized crystals containing fluorine donors, which suggest that hydrogen is a shallower donor than fluorine in TiO2 (rutile) crystals. The hydrogen EPR signal is easily observed during illumination in crystals that do not contain fluorine. 报告人简介：Dr. Shan Yang received his PhD in physics from West Virginia University in May 2010, and is currently a senior research associate at Case Western Reserve University. His research experience and interest spans from optical materials to biomedical optics, including characterization of the point defects in semiconductors using magnetic resonance technologies, R& D Raman based medical instruments for diagnosis of Gout Arthritis disease, and development of sophisticated high-sensitive nonlinear optical multi-modal imaging and microspectroscopy system based on three-color femtosecond Coherent Anti-Stokes Raman Scattering (CARS). His work in TiO2 has led to the systematic characterization of a series defects in this versatile semiconductor material including native oxygen vacancies, self-trapped electrons and holes, and silicon impurity. His discovery of hydrogen and fluorine donors for the first time has corrected the misunderstanding of these defects in the literature for over 50 years. 信息光子学与光通信国家重点实验室信息光子学与光通信研究院校学术委员会 http://portal.bupt.edu.cn//html/main/col51/2014-09/16/20140916143601675583232_1.html

学术报告通知:光学材料的点缺陷研究