报告题目: Quantum Cones Formation in Semiconductors by Laser Radiation: Experiments, Modeling and Application

　　报告人: Arturs Medvids (Professor,Riga Technical University, Latvia)

　　时间: 2014年5月9日 (星期五) 下午: 15:30

　　地点: 中科院半导体研究所图书馆101会议室

　　Abstract: Nowadays, nanostructures are one of the most investigated objects in semiconductor physics, especially due to Quantum confinement effect in quantum dots (0D), quantum wires (1D) and quantum wells (2D). A new laser method elaborated for quantum cones formation in semiconductors is reported. Quantum cones on the surface of elementary semiconductors Si and Ge single crystals, and on a surface of of Si1-xGex (x=0.3 and x=0.4) and Cd1-xZnxTe (x=0.1) solid solutions were formed by fundamental frequency and second harmonic of Nd:YAG laser radiation. Strong change of the optical, mechanical and electrical properties of the semiconductors after irradiation by Nd:YAG laser are explained by the presence of Quantum Confinement Effect (QCE) in quantum cones. “Blue shift” of photoluminescence spectra and “red shift” of phonon LO line in Raman spectrum are explained by exciton and phonon QCE in quantum cones, correspondently. Asymmetry of the photoluminescence band in the spectrum of Si quantum cones is explained by 1D graded band gap structure. The first stage of the mechanism is characterized by the formation of a thin strained top layer, due to redistribution of point defects in temperature-gradient field induced by laser radiation. The second stage is characterized by mechanical plastic deformation of the stained top layer leading to arising of quantum cones due to heating up of the top layer.

　　Formed quantum cones can be applied for design of third generation solar cells, Si white light emitting diode, photodetector with selective or “bolometer” type spectral sensitivity and Si tip for field electron emitting with low work function.

　　Biography：Arturs Medvids现担任拉脱维亚里加技术大学技术物理研究所教授，长期从事研究半导体材料包括Si，Ge，GeSi/Si，InSb，Te，CdTe，CdZnTe，SiC和ZnO等在非齐次(均匀)电场、磁场和温度场非平衡条件下的性质；半导体、金属(CoSi2)和电介质(SiO2和Si3N4)中的输运过程；强激光辐射和半导体的相互作用；利用激光照射在半导体表面生长纳米结构。已经发表474多篇学术著作和专利(包括专利74项，5本专著的专题论文作者)。