准相位匹配PPMgLN光参量振荡技术

 理论上分析了PPMgLN光参量振荡波长调谐特性，计算了泵浦阈值和转换效率。准相位匹配情况下，周期调谐是获得中红外波长调谐有效方法之一。采用高斯光束泵浦，当泵浦功率密度超过阈值泵浦功率密度约6.5倍时，可以获得最高转换效率，约71%。采用1 064 nm激光泵浦多周期PPMgLN晶体，实验上获得了波长调谐范围2.7~4.8 mm，当泵浦功率为8 W时，在波长3.7 mm处激光输出功率超过1.6 W，斜效率超过20%，相应的转换效率约为69%，与理论分析基本一致。     

极低剪切速率下聚丙烯酰胺溶液在毛细管中的流变特性 Ⅱ.毛细管尺寸和盐浓度对流变性能的影响

流变性能;流变行为;极低剪切速率下聚丙烯酰胺溶液在毛细管中的流变特性 Ⅱ.毛细管尺寸和盐浓度对流变性能的影响     

氧化锌表面包覆Sn6O4(OH)4的制备及其在锌镍电池中的应用

采用水热-共沉淀法在氧化锌表面包覆锡化合物,利用扫描电子显微镜（SEM）、X射线衍射（XRD）和能谱分析对制备的包覆ZnO材料进行表征。结果表明：XRD表明附着在氧化锌表面的是Sn₆O₄（OH）₄,且结晶度较好;SEM测试显示在pH=12条件下,Sn₆O₄（OH）₄能够很好地附着在氧化锌颗粒表面;能谱分析显示组成物中的元素包含Zn、Sn、O三种元素。利用循环伏安曲线、电化学阻抗谱（EIS）、倍率充放电技术对包覆ZnO材料进行了电化学性能的测试,结果表明：包覆Sn₆O₄（OH）₄的ZnO可以提高锌负极的耐蚀性能,增大电荷转移电阻（R_ct）;锌电极覆Sn₆O₄（OH）₄量为3%时充放电效率最佳,在0.2C充放循环40次后充放电循环保持率仍有70%。     

An AlGaN/GaN HEMT with a reduced surface electric field and an improved breakdown voltage

A reduced surface electric field in an AlGaN/GaN high electron mobility transistor(HEMT) is investigated by employing a localized Mg-doped layer under the two-dimensional electron gas(2-DEG) channel as an electric field shaping layer.The electric field strength around the gate edge is effectively relieved and the surface electric field is distributed evenly as compared with those of HEMTs with conventional source-connected field plate and double field plate structures with the same device physical dimensions.Compared with the HEMTs with conventional sourceconnected field plates and double field plates,the HEMT with a Mg-doped layer also shows that the breakdown location shifts from the surface of the gate edge to the bulk Mg-doped layer edge.By optimizing both the length of Mg-doped layer,L m,and the doping concentration,a 5.5 times and 3 times the reduction in the peak electric field near the drain side gate edge is observed as compared with those of the HEMTs with source-connected field plate structure and double field plate structure,respectively.In a device with V GS = -5 V,L m = 1.5 μm,a peak Mg doping concentration of 8×10 17cm-3 and a drift region length of 10 μm,the breakdown voltage is observed to increase from 560 V in a conventional device without field plate structure to over 900 V without any area overhead penalty.     

金属锌电沉积过程的分形研究

对金属锌电沉积过程中的二维枝晶生长进行了研究,分析了外加电压、电解质浓度以及温度等实验条件对电沉积产物形貌及其分形维数的影响.结果表明,随着外加电压的增大,沉积产物形貌的变化趋势为由开放的分枝结晶向较为致密的生长形貌转变;随着硫酸锌浓度的增大,沉积产物具有分叉结构的致密纤维状枝晶簇和较为粗壮的开放型规则的分叉状枝晶,分形维数发生相应的变化;随着温度的升高,沉积产物的枝晶呈均匀化、致密化,沉积产物分形维数呈明显增大的趋势.     

Monte Carlo法计算机模拟研究冰晶石-氧化铝熔体结构

冰晶石-氧化铝熔液是由各类离子质点组成的相当复杂的混合物,研究此熔盐系的离子结构对探讨铝电解机理和氧化铝在冰晶石熔液中的溶解机理具有重要意义^[1],由于冰晶石-氧化铝的熔点高和腐蚀严重,一些衍射技术难以用于此熔盐系液态微观结构性质的研究。     

有色金属冶炼中含砷物料的除砷技术研究现状

综述了砷对冶金、环境以及人类的危害,阐述了冶金工业中含砷物料的除砷技术的发展现状,介绍了各种技术的原理、应用,分析了各种技术的优缺点,展望了除砷技术的发展方向。     

A novel 4H-SiC lateral bipolar junction transistor structure with high voltage and high current gain

In this paper, a novel structure of a 4H-SiC lateral bipolar junction transistor (LBJT) with a base field plate and double RESURF in the drift region is presented. Collector-base junction depletion extension in the base region is restricted by the base field plate. Thin base as well as low base doping of the LBJT therefore can be achieved under the condition of avalanche breakdown. Simulation results show that thin base of 0.32 μm and base doping of 3×1017 cm-3 are obtained, and corresponding current gain is as high as 247 with avalanche breakdown voltage of 3309 V when the drift region length is 30 μm. Besides, an investigation of a 4H-SiC vertical BJT (VBJT) with comparable breakdown voltage (3357 V) shows that the minimum base width of 0.25 μm and base doping as high as 8×1017 cm-3 contribute to a maximum current gain of only 128.     

An AlGaN/GaN HEMT with enhanced breakdown and a near-zero breakdown voltage temperature coefficient

An AlGaN/GaN high-electron mobility transistor(HEMT) with a novel source-connected air-bridge field plate(AFP) is experimentally verified.The device features a metal field plate that jumps from the source over the gate region and lands between the gate and drain.When compared to a similar size HEMT device with a conventional field plate(CFP) structure,the AFP not only minimizes the parasitic gate to source capacitance,but also exhibits higher OFF-state breakdown voltage and one order of magnitude lower drain leakage current.In a device with a gate to drain distance of 6 μm and a gate length of 0.8 μm,three times higher forward blocking voltage of 375 V was obtained at VGS =-5 V.In contrast,a similar sized HEMT with a CFP can only achieve a breakdown voltage no higher than 125 V using this process,regardless of device dimensions.Moreover,a temperature coefficient of 0 V/K for the breakdown voltage is observed.However,devices without a field plate(no FP) and with an optimized conventional field plate(CFP) exhibit breakdown voltage temperature coefficients of-0.113 V/K and-0.065 V/K,respectively.     

基于周期极化钽酸锂晶体的光参变振荡器技术研究

对基于周期极化钽酸锂(PPLT)晶体的光参变振荡器(OPO)技术进行了理论分析和实验研究,通过三波混频耦合波方程组,计算了PPLT-OPO的波长调谐曲线.分别研究了信号光单谐振结构(SSRO)和闲频光单谐振结构(ISRO)下,PPLT-OPO的中红外激光输出特性.当Nd:YAG激光器输出的1.064 μm激光抽运功率为...