温度对GaSb/GaAs量子点尺寸分布的影响

采用低压金属有机物化学气相沉积 (LP-MOCVD) 法制备GaSb/GaAs量子点。通过对不同生长温度的样品进行分析发现温度的变化对GaSb/GaAs量子点的相位角无明显影响,量子点的形状是透镜型。由于量子点特殊的应力分布,可实现量子点的"自限制"生长。量子点的化学势不连续性以及Ostwald熟化机制的影响使得量子点尺寸分布在一定范围内不连续,会出现两种尺寸模式的量子点生长。Sb原子的表面迁移率对GaSb/GaAs量子点生长有较大的影响。升高温度可有效改善量子点的分立性,在升温过程中量子点体现出其熟化过程,高温时表面原子的解析附作用对量子点尺寸和密度的影响较大。     

白鱀豚的保护对策应该调整

白暨豚属鲸目、齿鲸亚目、淡水豚总科,仅分布于我国长江中下游,是我国的特产动物。50年代白暨豚的数量还较多,但随着长江的开发利用,人类活动加剧,白暨豚的数量迅速减少。根据中国科学院水生生物研究所的调查,1986年为300头左右,1990年降至200头左右,到1995年已不足100头了。它正成为世界鲸类动物中最濒危的一种,濒临灭绝。白暨豚的保护问题一直引起国内外各方人士和我国政府的极大重视,我国把白暨豚列为一级保护动物。国内外专家曾多次召开白暨豚保护的专题讨论会,在1986年召开的“国际淡水豚生物学和物种保护”学术讨论会上,提出了保护白暨豚的三大措施,1.建立两个“半自然保护区”,即湖北石首天鹅洲白暨豚半     

High-crystalline GaSb epitaxial films grown on GaAs(001) substrates by low-pressure metal–organic chemical vapor deposition

Orthogonal experiments of Ga Sb films growth on Ga As(001)substrates have been designed and performed by using a low-pressure metal–organic chemical vapor deposition(LP-MOCVD)system.The crystallinities and microstructures of the produced films were comparatively analyzed to achieve the optimum growth parameters.It was demonstrated that the optimized Ga Sb thin film has a narrow full width at half maximum(358 arc sec)of the(004)ω-rocking curve,and a smooth surface with a low root-mean-square roughness of about 6 nm,which is typical in the case of the heteroepitaxial single-crystal films.In addition,we studied the effects of layer thickness of Ga Sb thin film on the density of dislocations by Raman spectra.It is believed that our research can provide valuable information for the fabrication of high-crystalline Ga Sb films and can promote the integration probability of mid-infrared devices fabricated on mainstream performance electronic devices.     

白鳍豚听觉灵敏度的研究

本文采用文献[1]、[2]所采用的训练方法,对一头人工饲养的白鳍豚的听觉灵敏度进行了测量,得到了频率范围为1kHz～200kHz的听阈曲线。实验表明,白鳍豚最敏感的频率范围为16kHz～48kHz,这一范围的阈值为-38～-44dB,其听力频率上限超过200kHz,下限低于1kHz。文中还对实验中白鳍豚的一些行为进行了讨论。     

白暨豚体表致病菌的分离鉴定

从白暨豚体表皮肤溃烂处分离得到一株嗜水单气胞杆菌，经过纯化培养，电镜观察，生理生化鉴定及毒力试验，证明该菌为白暨豚体表皮肤致病菌，属于嗜水气单胞菌嗜水亚种。药物抑菌试验表明；广谱抗菌素类药物对该菌都有较强的抑制生长能力。     

Nucleation of GaSb on GaAs （001） by low pressure metal-organic chemical vapor deposition

The initial growth stage of GaSb on GaAs(001) by low pressure metal–organic chemical vapor deposition(MOCVD)is investigated. The dependence of the nucleation on growth temperature, growth pressure, and vapor V/III ratio is studied by means of atomic force microscopy. The nucleation characteristics include the island density, size, and size uniformity distribution. The nucleation mechanism is discussed by the effects of growth temperature, growth pressure, and vapor V/III ratio on the density, size, and size uniformity of GaSb islands. With the growth temperature increasing from 500℃ to610℃ and the growth pressure increasing from 50 mbar to 1000 mbar(1 mbar = 105Pa), the island density first increases and then decreases; with the V/III ratio increasing from 0.5 to 3, the trend is contrary.     

The design and numerical analysis of tandem thermophotovoltaic cells

In this paper, numerical analysis of GaSb （Eg = 0.72 eV）/Gao.84Ino.16Aso.14Sbo.86 （Eg = 0.53 eV） tandem thermopho- tovoltaic （TPV） cells is carried out by using Silvaco/Atlas software. In the tandem cells, a GaSb p-n homojunction is used for the top cell and a GalnAsSb p-n homojunction for the bottom cell. A heavily doped GaSb tunnel junction connects the two sub-cells together. The simulations are carried out at a radiator temperature of 2000 K and a cell temperature of 300 K. The radiation photons are injected from the top of the tandem cells. Key properties of the single- and dual-junction TPV cells, including I-V characteristic, maximum output power （Pmax）, open-circuit voltage （Voc）, short-circuit current （/~sc）, etc. are presented. The effects of the sub-cell thickness and carrier concentration on the key properties of tandem cells are investigated. A comparison of the dual-TPV cells with GaSb and GalnAsSb single junction cells shows that the Pmax of tandem cells is almost twice as great as that of the single-junction cells.