Centimetre-Long Single Crystalline ZnO Fibres Prepared by Vapour Transportation

Centimetre-long ZnO fibres are synthesized by vapour transportation via thermal evaporation of ZnO powders. The growth process is carried out in a graphite crucible, in which ZnO powder is loaded as the source material, and a silicon wafer is positioned on the top of the crucible as the growth substrate. During the growth process, the source temperature is kept at 800℃ and the substrate temperature is kept at 600℃. Typical growth time to obtain centimetre-long ZnO fibres is 5-10 hours. Scanning electron microscopy （SEM）, x-ray diffraction （XRD）, transmission electron microscopy （TEM）, and selected area electron diffraction （SAED） measurement results show that ZnO fibres are single crystalline with high crystalline quality and very low defects concentration.     

Degradation of Ultra-Thin Gate Oxide NMOSFETs under CVDT and SHE Stresses

Degradation of device under substrate hot-electron (SHE) and constant voltage direct-tunnelling (CVDT)stresses are studied using NMOSFET with 1.4- nm gate oxides. The degradation of device parameters and the degradation of the stress induced leakage current (SILC) under these two stresses are reported. The emphasis of this paper is on SILC and breakdown of ultra-thin-gate-oxide under these two stresses. SILC increases with stress time and several soft breakdown events occur during direct-tunnelling (DT) stress. During SHE stress, SILC firstly decreases with stress time and suddenly jumps to a high level, and no soft breakdown event is observed. For DT injection, the positive hole trapped in the oxide and hole direct-tunnelling play important roles in the breakdown. For SHE injection, it is because injected hot electrons accelerate the formation of defects and these defects formed by hot electrons induce breakdown.     

Cl-ClO催化循环圈的从头算研究

采用分子轨道从头算方法,在B3LYP/6-311 G(3df)和G2水平上研究了极地平流层臭氧损耗的一个基本过程.计算结果明显支持Cl-ClO催化循环圈机理,并且从能量角度解释了了臭氧破坏的基本原因.还对循环圈中各个反应的反应能,生成焓,相对吉布斯自由能做了计算,计算结果相互协调都说明了Cl-ClO催化循环圈破坏臭氧机理的正确性.     

两种以Znq2为基体的新型电致发光材料的合成与性能

以8-羟基喹啉为配体的金属配合物是一种性能优良的有机电致发光材料,其中有关8-羟基喹啉铝(Alq₃)研究已有大量报道,8-羟基喹啉锌(Znq₂)研究还有待发展。介绍了两种以Znq₂为基体的新型有机电致发光材料Znq₂(H₂O)₂和(Znq₂)₄的合成方法。用IR、XRD、TG、DTA和荧光测试方法进行表征与分析表明:Znq₂(H₂O)₂和(Znq₂)₄的玻璃化温度(T_g)分别为104.2℃和204.9℃;在161℃下Znq₂(H₂O)₂脱去水分子成为Znq₂,在361℃高温下四聚体(Znq₂)₄裂解为单体Znq₂;Znq₂(H₂O)₂和(Znq₂)₄具有很好的发光性能,在光致发光谱中λ_max分别是505,550nm。     

Deep InP Gratings for Opto-Electronic Devices Etched by C12/CH4/Ar Inductively Coupled Plasma

Deep InP gratings are etched by C12/CH4/Ar inductively coupled plasma （ICP） at room temperature. A comparison is made between SiNz mask patterns formed by wet and dry etching. SF6 reactive ion etching is adopted for smooth and vertical sidewall. The etching conditions of C12/CH4/Ar ICP are optimized for high anisotropy, and a 1.7-μm-deep InP grating with an aspect ratio of 10：1 is demonstrated. The technique is then used for the fabrication of 1.55-μm laterally coupled distributed feedback A1GMnAs-InP laser.     

稀疏阈值的超分辨率图像重建

为了解决基于字典学习的超分辨重构算法耗时过长的问题,提出了基于稀疏阈值模型的图像超分辨率重建方法。首先,将联合字典理论与图像块稀疏阈值方法相结合,训练得到高、低分辨率过完备图像字典对。接着,通过稀疏阈值OMP算法对图像特征块进行稀疏表示。然后,通过高分辨率字典重构出初始的超分辨图像。最后,通过改进迭代反投影算法对初始的超分辨图像进行全局优化,从而进一步提高图像重构质量。实验结果表明,超分辨图像重构平均峰值信噪比(PSNR)为30.1 d B,平均结构自相似度(SSIM)为0.937 9,平均计算时间为10.2 s。有效提高了超分辨重构的速度,改善了重构高分辨图像的质量。     

Efficient Laser-Diode End-Pumped Passively Q-Switched Mode-Locked Yb：LYSO Laser Based on SESAM

We report an efficient Q-switched laser action based on a semiconductor saturable absorber mirrors （SESAMs） as passively Q-switched laser starter and a Yb：LYSO alloyed crystal as gain material pumped directly by 974nm InGaAs laser diodes. The output pulse duration is measured to be about 7μs, while the average power and the repetition rate of the pulse chain are about 0.92 W and 6.2 kHz, respectively, under 12.5 W absorbed pumping power. The Q-switched mode-locked pulse train is also observed in this setup. The laser performance shows that Yb：LYSO is a promising laser gain medium for laser-diode pumped compact solid-state lasers.     

高温高压下β相硼的电导率测量

 硼在高压下具有复杂的结构和多样的物理性质,对其结构和性质的深入研究具有很重要的意义,一直引起理论和实验研究领域的关注。高压下进行电学性质测量是获得物质物理性质的有效手段,利用集成在金刚石对顶砧上的微电路,在高压下和两个不同温度范围内对β相硼进行了电导率测量,分析了导电机制随压力的变化规律。在0～28.1 GPa范围内,β相硼的电导率随着压力的增大是逐渐增大的,卸压后样品的电导率不能回到最初的状态,是一个不可逆的变化过程;由室温到423 K的范围内,β硼的电导率随着温度的不断增加有明显的上升趋势,并且随着压力的升高,电导率变化逐渐加快。此外,对样品在14.5 GPa和18.6 GPa压力下,用溅射到金刚石对顶砧上的氧化铝薄膜做绝热层,对样品进行了激光加热实验,最高温度达到2 224 K,电导率随着温度的上升而增大,结果显示,β相硼的电学特征仍然属于半导体的特征范围内。     

采用HfO2/SiO2溶胶-凝胶薄膜制备衍射光栅

采用溶胶-凝胶方法制备了具有光敏性的HfO2/SiO2溶胶-凝胶薄膜,并利用其光敏性制备了衍射光栅.采用XPS分析了薄膜的成份,证实了Hf元素的存在.并用椭偏仪测试了薄膜的折射率,结果证实了HfO2的加入确实提高了体系的折射率.利用其光敏性,采用X射线作曝光光源通过掩模进行曝光,利用曝光部分与未曝光部分的溶解度差,在薄膜上制备了高为0.8 μm、周期为1 μm的衍射光栅.     

应用于微电容超声换能器的信号处理电路设计*

针对微电容超声换能器的输出信号特征及检测要求,文中设计了换能器的微弱信号处理电路,包括基于跨阻的微弱电流信号检测和多重反馈带通滤波电路。通过搭建水下测试平台,对电路性能及功能进行实际测试,并进行水下测距实验。实验结果表明,该电路可对微电容超声换能器输出的400 k Hz信号进行检测放大与滤波;电路的线性度为0.18%,滤波电路中心频率为396 k Hz,带宽为55 k Hz。该电路可用于CMUT的接收信号处理并应用于超声测距及成像的前端信号处理。