多频GNSS抗多径天线的设计和实现

多径效应是影响卫星导航接收机测量精度的一个主要误差源,可以采用改进天线结构的方法,提高抗多径性能。本文从天线抗多径理论入手,描述了一种多频抗多径天线的设计和实现。测试结果表明,该天线具有良好的抗多径效果。     

High-yield synthesized silver orthophosphate nanowires and their application in photoswitch

Large-scale, high-purity and uniform silver orthophosphate (Ag3PO4) nanowires had been synthesized by a facile hydrothermal method without employing any surfactants or templates for the first time. The nanowires were single-crystalline with lengths up to several micrometers. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy were used to characterize the morphology and structure of the as-prepared products. The as-prepared Ag3PO4 nanowires exhibited linear current-voltage (Ⅰ-Ⅴ) characteristics and excellent photoresponse. As the light was switched on and off, the currents could be reversibly switched between high and low value at the voltage of 0.1 V, which will find wide application in optoelectronic nanodevices.     

应用于大功率激光二极管列阵的单片集成微通道制冷热沉

介绍了一种应用于大功率激光二极管列阵的新型单片集成微通道制冷热沉.这种热沉已制造并经过测试.10叠层的激光二极管列阵的热阻为0.121℃/W.相邻两个激光条的间距是1.17mm.在20%高占空比条件下,波长为808nm左右,峰值功率可以达到611W.     

Material Growth and Device Fabrication of GaN-Based Blue-Violet Laser Diodes

Studies on first GaN-based blue-violet laser diodes(LDs) in China mainland are reported.High quality GaN materials as well as GaN-based quantum wells laser structures are grown by metal-organic chemical vapor deposition method.The X-ray double-crystal diffraction rocking curve measurements show the fullwidth half maximum of 180″ and 185″ for (0002) symmetric reflection and (10-12) skew reflection,respectively.A room temperature mobility of 850cm2/(V·s) is obtained for a 3μm thick GaN film.Gain guided and ridge geometry waveguide laser diodes are fabricated with cleaved facet mirrors at room temperature under pulse current injection.The lasing wavelength is 405.9nm.A threshold current density of 5kA/cm2 and an output light power over 100mW are obtained for ridge geometry waveguide laser diodes.     

大直径直拉硅单晶中的空洞型原生缺陷

空洞型 ( Void)原生缺陷在大直径直拉硅单晶中的重要性日渐突出。本文在论述大直径硅单晶中 Void缺陷基本性质的同时 ,详细综述了这类缺陷的控制方法以及它与轻元素 (氧、氮、碳、氢 )杂质的相互作用 ,并简要讨论了关于 Void缺陷的研究方法和今后的研究方向。     

硝酸盐作为酸法地浸氧化剂的研究

硝酸盐作为酸法地浸采铀氧化剂的研究结果表明 ,硝酸根可有效地氧化地浸吸附尾液中的Fe2 ,但其动力学性能较 H2 O2 差 ;硝酸根能有效氧化浸出矿石中难溶的四价铀。硝酸盐作为浸出氧化剂 ,能满足地浸工艺的需要     

H型结构垂直腔面发射激光器

报道了一种结构新颖的Ｈ型垂直腔面发射激光器。器件是由钨丝掩膜一次质子轰击和选择腐蚀相结合制备的，实验已实现在脉宽为２０μｓ，占空比为１１０的脉冲电流条件下的室温激射。     

Investigation of pattern coating on mould roller in roller-reversal imprint process

In order to prepare large area micropatterns with certain profile (certain aspect ratio) on kinds of substrates, especially on flexible substrate, a novel roller-reversal imprint (RRI) process is proposed, which starts with pattern coating of an ink (mostly a liquefied electronics materials, such as a semiconductor polymer) on a mould roller and ends with transferring the ink already patterned on the roller to the substrate. One of the critical challenges in RRI process is ensuring ink pattern coating and full filling to the microcavities on mould roller, which is one of the preconditions to achieve the pattern transferred on substrate with precise profile. In this paper, an ink coating model is established to reveal the ink filling situations versus different profile of microcavities on mould roller. Simulations show that, in the coating process, as the contact angle of ink on mould increasing, three basic filling situations, i.e., full filling, partial filling, and non-filling, will occur. In order to demonstrate the requirement of full filling, critical contact angle for full filling is proposed to distinguish the full filling and partial filling, and it is deeply dependant on the cross-sectional parameters (such as linewidth and the aspect ratio) of microcavities on mould roller. The critical contact angle is the watershed between full filling and partial filling, so it can be used as a guideline to choose the appropriate match between the surface energy of ink and mould to achieve full filling in RRI process. Experiments prove that the ink filling model and its simulation results are basically right, the cross-sectional parameters of microcavities on mould play great important roles to the critical contact angle, and only when the actual contact angle is smaller than the corresponding critical value, full filling can be obtained.     

A closed-form distributed source localisation method using TDOA and GROA

This paper proposes a closed-form distributed passive source localisation method using time difference of arrival (TDOA) and gain ratios of arrival (GROA) measurements. After removing the unknown parameters in TDOA equations by using GROA measurements, the proposed method applies two-step weighted least-square (LS) minimisations. First, the TDOA and GROA equations are transformed into a set of pseudo-linear equations by introducing additional parameters, and a weighted LS estimation is used to obtain a rough estimate; secondl, this method exploits additional parameters to refine the estimate through another weighted LS estimation. The application of weighting matrix leads to an approximate maximum likelihood estimator and produces a substantial improvement in source localisation accuracy. Both the theoretical analysis and simulation results indicate that the proposed method can achieve the Cramer–Rao Lower Bound at a moderate noise level and outperform the existing methods in terms of localisation accuracy.     

CCD多晶硅层间复合绝缘介质研究

电荷耦合器件(CCD)多晶硅交叠区域绝缘介质对成品率和器件可靠性具有重要的影响。将氮化硅和二氧化硅作为CCD多晶硅层间复合绝缘介质,采用扫描电子显微镜(SEM)和电学测试系统研究了多晶硅层间氮化硅和二氧化硅复合绝缘介质对CCD多晶硅栅间距和多晶硅层间击穿电压的影响。研究结果表明,多晶硅层间复合绝缘介质中的氮化硅填充了多晶硅热氧化层的微小空隙,可以明显改善绝缘介质质量。多晶硅层间击穿电压随着氮化硅厚度的增加而增大,但太厚的氮化硅会导致CCD暗电流明显增大。由于复合绝缘介质质量好,可以减小CCD多晶硅的氧化厚度。