半导体悬浮体系光催化分解有机磷化合物

本文研究了半导体悬浮体系光催化分解有机磷化合物的条件,只有在光照、催化剂和氧同时存在的条件下才能有效地光催化分解有机磷化合物;测量了两种有机磷化合物在各种半导体催化剂上的分解速率,反应速率与催化剂的种类和表面性质有关;对光催化分解马拉硫磷的反应机理进行了初步探讨。     

Synthesis of aromatic poly(thioether ketone)

Aromatic poly(thioether ketone)s were prepared by the direct polycondensation of aromatic dicarboxylic acids with aryl compounds containing ether or sulfide structures using phosphorus pentoxide/methanesulfonic acid (PPMA) as a condensing agent and solvent. Polycondensation proceeded smoothly and produced aromatic poly(thioether ketone)s with inherent viscosities up to 0.73 dL/g. The synthesis of substituted aryl ketones by the reaction of substituted benzoic acids with aryl compounds in PMMA was studied in detail to demonstrate the feasibility of the reaction for polymer formation. The thermogravimetry of the aromatic poly(thioether ketone)s showed a 10% weight loss in air and nitrogen at around 450 and 460°C, respectively. © 1992 John Wiley & Sons, Inc.     

Pt coated Cr2O3 thin films for resistive gas sensors

The resistive response of atomic layer deposited thin epitaxial α-Cr₂O₃(0 0 1) films, to H₂ and CO in air, was studied. The films were covered with Pt nanoislands formed by electron-beam evaporation of a sub-monolayer amount of the material. The gas measurements were performed at 250°C and 450°C. These temperatures led to different proportion of chemical states, Pt²⁺ and Pt⁴⁺, to which the Pt oxidized. The modification was ascertained by the X-ray photoelectron spectroscopy method. As a result of the modification, the response was fast at 250°C, but slowed at 450°C. A disadvantageous abundance of Pt⁴⁺ arising at 450°C in air could be diminished by high-vacuum annealing thus restoring the response properties of the system at 250°C.      

射频溅射法制备Pb_(1-x)Co_xSe薄膜及物性研究

利用复合靶共溅射法制备了半磁性半导体 Ｐｂ１－ ｘ Ｃｏｘ Ｓｅ 薄膜．研究了薄膜的成分结构以及电阻率温度特性和磁化率温度特性间的关系．结果表明：由于 Ｃｏ 离子介入, Ｐｂ１－ ｘ Ｃｏｘ Ｓｅ 发生了由金属特性向半导体特性的转变,在充分低的温度下,并伴有磁相转变．磁相转变温度与磁性离子浓度相关,磁化率的相对变化幅度与磁性离子浓度有关     

Delayed breakdown diode and its optimal design for solid state picosecond closing switch

We study a Si-based diode with a p⁺nn⁺ structure for picosecond semiconductor closing switch and discuss the physical process, which underlies the operation principle of high-power closing switch based on a delayed breakdown diode (DBD). From the results of numerical simulations and theoretical analysis, single device has demonstrated reliable operation at 2.3 kV, 89 ps risetime, and high output dV/dt(30 kV/ns). As a contribution to the optimal design, some conclusions about trade-off are drawn by changing structure parameters and physical parameters.     

半导体光放大器的光-光互作用及其应用

半导体光放大器（SOA）中的非线性系数约为普通光纤的10^9，为光子晶体光纤的10^7，而且有4种光-光互作用，即交叉增益调制（XGM）、交叉相位调制（XPM）、交叉偏振调制（XSM）及四波混频（FWM），可以灵活地组成各种光信号处理器件，如波长变换器、全光触发器、全光逻辑、全光时钟恢复、全光缓存器……等，正成为整个光信号处理的基础。文章介绍了它们的原理和简单应用。     

直接扣除法测量半导体光放大器频率响应

在光电子器件散射参量定义的基础上建立了基于直接扣除法的半导体光放大器频率响应测量系统,测量中通过扣除激光器和探测器系统的频率响应,得到放大器固有的频率响应。对InGaAsP体材料行波腔半导体光放大器样品进行了测量,得到了放大器在不同注入光功率和不同偏置电流下的频率响应曲线。这些曲线很好地反应了半导体光放大器的增益饱和和噪声特性,进一步分析发现半导体光放大器对低频调制信号的放大能力弱于对高频信号的放大能力,分析认为其原因在于半导体光放大器的载流子寿命有限导致低频信号长时间消耗载流子时,载流子数量无法及时恢复,从而使得增益降低。     

Fluctuation of semiconductor surface potential in Si-SiO<Subscript>2</Subscript> structure after irradiation and subsequent annealing

Fluctuations of the semiconductor surface potential in a Si-SiO₂ structure, caused by irradiation with different high-energy particles (50 MeV electrons and 40 keV arsenic ions) and subsequent annealing, have been studied by measuring the semiconductor interface state parameters. It is established that the fluctuation of the semiconductor surface potential decreases slightly, from 0.049 V to 0.044 V, after irradiation, while a considerable increase is observed after annealing. For the samples irradiated by arsenic ions, the increase in fluctuation is much larger (0.096 V) than that for the electron-irradiated samples (0.06 V).     

Trap elimination and reduction of size dispersion due to aging in CdS<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Se<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript> quantum dots

Quantum Dots of CdS _x Se_1−x embedded in borosilicate glass matrix have been grown using Double-Step annealing method. Optical characterization of the quantum dots has been done through the combinative analysis of optical absorption and photoluminescence spectroscopy at room temperature. Decreasing trend of photoluminescence intensity with aging has been observed and is attributed to trap elimination. The changes in particle size, size distribution, number of quantum dots, volume fraction, trap related phenomenon and Gibbs free energy of quantum dots, has been explained on the basis of the diffusion-controlled growth process, which continues with passage of time. For a typical case, it was found that after 24 months of aging, the average radii increased from 3.05 to 3.12 nm with the increase in number of quantum dots by 190% and the size-dispersion decreased from 10.8% to 9.9%. For this sample, the initial size range of the quantum dots was 2.85 to 3.18 nm. After that no significant change was found in these parameters for the next 12 months. This shows that the system attains almost a stable nature after 24 months of aging. It was also observed that the size-dispersion in quantum dots reduces with the increase in annealing duration, but at the cost of quantum confinement effect. Therefore, a trade off optimization has to be done between the size-dispersion and the quantum confinement.     

Combinatorial synthesis and characterization of a ternary epitaxial film of Co and Mn doped Ge (0 0 1)

We report combinatorial molecular beam epitaxy synthesis and properties of a ternary epitaxial film of Co and Mn co-doped Ge grown on Ge (0 0 1) substrate. Structural effects were examined in situ by reflection high-energy electron diffraction and ex situ by microbeam X-ray diffraction techniques, and magnetic properties were probed by using magnetooptic Kerr effect. Ternary epitaxial phase diagrams have been studied for total doping concentrations up to 30 at.%, where regions of coherent epitaxy and rough disordered growth and those of near room temperature ferromagnetic ordering have been identified.