一种获得GaAs/GaAlAs多量子阱材料带边附近折射率色散关系的方法

本文提供了一种在GaAs/GaAlAs多量子阱(MQW)材料的直接带边附近折射率参数色散关系的获得方法。其特点是在多层介质膜系统中用光学传递矩阵对MQW进行处理的基础上引入室温激子振荡因子,然后对材料的实验反射谱进行拟合。这种色散关系对于光电器件设计及其理论期望来讲是十分重要的。这种方法除能得到折射率实部与虚部的色散关系外,还可得到激子共振吸收谱。 关键词：     

脉冲激光气相沉积法制备钴纳米薄膜实验研究

采用脉冲激光沉积技术制备了钴纳米薄膜,分析和讨论了不同背景气压和脉冲频率对钴纳米薄膜表面形貌的影响及纳米微粒的形成机理。实验结果表明：在低背景气压下,等离子体羽辉自身粒子之间的碰撞占主导作用,容易形成液滴;在较高背景气压下,等离子体羽辉边缘粒子和背景气体粒子之间的碰撞占主导作用,容易形成小岛并凝聚成微颗粒;在4Hz的脉冲重复频率和5Pa背景气压下生长出单分散性良好的钴纳米颗粒。     

钙钛矿氧化物异质结的光电特性研究进展

光与物质相互作用可以产生各种光学现象,其中光电效应是非常重要的现象之一.文中集中回顾了文章作者在钙钛矿氧化物异质结的光电效应研究中的进展.在钙钛矿氧化物异质结中,分别观测到了传统的纵向光电效应和反常的横向光电效应,并通过对含时的漂移-扩散方程的自洽求解,从理论上分别揭示了钙钛矿氧化物异质结纵向和横向光电效应的动态过程.文章首先介绍了钙钛矿氧化物异质结纵向光电效应的研究进展,接着概述了钙钛矿氧化物异质结横向光电效应研究的进展.最后对氧化物异质结的纵向和横向光电效应的潜在应用前景进行展望.     

Ultrafast Photoelectric Effects in Heterojunctions of La0.7Sr0.3MnO3 and Si

Ultrafast photoelectric effects have been observed in p-n heterojunctions of La0.7Sr0.3MnO3(LSMO)/Si and LSMO/SrTiO3_/Si for the first time. The rise time was about 1 ns and the full width at half maximum was about 2ns for the photovoltaic pulse when the heterojunction was irradiated by a laser of -25 ps pulse duration and 1064 nm wavelength. The photovoltaic sensitivity was as large as 435 mV//mJ for a 1064 nm laser pulse. No such pulse was observed with irradiation from a pulsed 10.6 μm CO2 laser.     

The third-order optical nonlinearity of the stainless steel doped SrTiO_3 thin film grown by L-MBE

Stainless steel-doped SrTiO3 thin films were fabricated by laser molecular beam epitaxy (L-MBE). Nonlinear optical property of the thin film was measured by the single beam Z-scan technique at the wavelength of 532 nm. Two two-phonon absorption coefficient and nonlinear refractive index were determined to be 9.37 x 10-7 m/W and 1.55 x 10-6 esu, respectively. The merit figure T was calculated to be 1.8, satisfying condition T < 1 for an optical switch. The thin film has a very promising prospect for the applications in optical device.     

研究表面物理的非线性光学方法

在表面科学的研究中,常常把吸附在表面上的分子的物理和化学性质视为最重要的事情,因此,对单层分子或亚单层分子的检测是必不可少的.为了这一目的,已经发展起了各种技术,但是只有少数可以用于探测吸附分子的微观性质,而且都有其局限性. 最近,随着可调谐激光器的进展,非线性光学光谱技术得到了迅速发展.这种技术既有很高的灵敏度,也有较好的分辨率,因而很自然地被用来做表面研究.Chen等发现,用表面相干反斯托克斯喇曼散射(CARS)谱可以灵敏地检测单层吸附分子[1].Heritage等[2]证实,微微秒喇曼增益谱可以用来获得薄膜和单层分子的喇曼谱.表…     

Ultraviolet Sensitive Ultrafast Photovoltaic Effect in Tilted KTaO3 Single Crystals

An ultraviolet sensitive ultrafast photovoltaic effect is observed in tilted 10° KTaO3 （KT） single crystals. The rise time of the transient photovoltaic pulse is 497.4 ps and the full width at half maximum is 974.6 ps under irradiation of a 266 nm laser pulse with 25 ps duration. An open-circuit photovoltage sensitivity of 328 mV/mJ and a photocurrent sensitivity of 460 mA/mJ are obtained. The experimental results demonstrate the potential applications of KT single crystals in ultraviolet detection.     

Oxygen Pressure Dependence of Properties of Epitaxial LaAlO3 Films Grown on Si （100）

Heteroepitaxial LaAlO3 films were grown on a SrTiO3/Si (100) substrate by laser molecular beam epitaxy under different oxygen pressures, and their properties such as crystallinity and electrical characteristics were experimentally investigated using the various measurement methods. The results show that most properties depend mainly on the deposition oxygen pressure. The crystallinity and the C-V and I-V characteristics can be greatly improved with the increasing oxygen deposition pressure. Moreover, after annealed at 1050~C in N2 ambient, the C-V and I-V characteristics of LAO films deposited at the lower oxygen pressure are also improved due to the decrease of oxygen vacancies in LAO films.     

Laser Molecular Beam Epitaxy Growth of BaTiO3 in Seven Thousands of Unit-Cell Layers

BaTiO3 thin films in seven thousands of unit-cell layers have been successfully fabricated on SrTiO3 （001） substrates by laser molecular beam epitaxy. The fine streak pattern and the undamping intensity oscillation of reflection high-energy electron diffraction indicate that the BaTiO3 film was layer-by-layer epitaxial growth. The measurements of scanning electron microscopy and atomic force microscopy show that surfaces of the BaTiO3 thin film are atomically smooth. The measurements of x-ray diffraction and transmission electron microscopy, as well as selected-area electron diffraction reveal that the BaTiO3 thin film is a c-oriented epitaxial crystalline structure.     

BaTiO3/SrTiO3超晶格的激光分子束外延生长与二阶光学非线性研究

使用激光分子束外延,在SrTiO3 (100)单晶衬底上成功生长了一系列c轴取向的,具有原子量级控制精度的BaTiO3/SrTiO3超晶格. 利用晶格失配导致的薄膜表面台阶密度的周期性变化,讨论了反射式高能电子衍射(RHEED)强度在BaTiO3层和SrTiO3层中的周期性调制. 系统研究了二阶非线性光学极化率同超晶格结构的关系. 实验测量和理论拟合结果表明,BaTiO3/SrTiO3超晶格的二阶非线性光学极化率显著增强,其最大值比BaTiO3体单晶提高一个数量级以上. 从应力导致的晶格畸变和极化增强出发,讨论了二阶光学非线性增强的物理机制.