半绝缘GaAs光电导开关非线性电脉冲超快上升特性研究

利用流体模型对光生载流子的输运进行了模拟研究,结果表明载流子在输运过程中形成的光激发电荷畴是产生电脉冲超快上升特性的主要原因.对光激发电荷畴的形成和吸收过程的进一步研究表明：1)形成过程中的光激发电荷畴增强了电子的浓度梯度;2)光激发电荷畴在被阳极吸收的过程中,光电导开关偏置电压的快速下降能促进电流上升速度.光激发电荷畴的形成和吸收两大过程共同作用下,形成了电脉冲的超快上升特性. 关键词： 光电导开关 非线性模式 光激发电荷畴 上升时间     

Two‐Way Molecular Switches with Large Nonlinear Optical Contrast

Molecular switches : Highly efficient acido‐ and photoswitchable frequency doublers (see scheme) based on the indolinooxazolidine core are studied by means of hyper‐Rayleigh experiments and quantum‐chemical calculations.

     

Protonmotive force: development of electrostatic drivers for synthetic molecular motors

Ferrocene has been investigated as a platform for developing protonmotive electrostatic drivers for molecular motors. When two 3-pyridine groups are substituted to the (rapidly rotating) cyclopentadienyl (Cp) rings of ferrocene, one on each Cp, it is shown that the (Cp) eclipsed, pi-stacked rotameric conformation is preferred both in solution and in the solid state. Upon quaternization of both of the pyridines substituents, either by protonation or by alkylation, it is shown that the preferred rotameric conformation is one where the pyridinium groups are rotated away from the fully pi-stacked conformation. Electrostatic calculations indicate that the rotation is caused by the electrostatic repulsion between the charges. Consistently, when the pi-stacking energy is increased pi-stacked population increases, and conversely when the electrostatic repulsion is increased pi-stacked population is decreased. This work serves to provide an approximate estimate of the amount of torque that the electrostatically driven ferrocene platform can generate when incorporated into a molecular motor. The overall conclusion is that the electrostatic interaction energy between dicationic ferrocene dipyridyl systems is similar to the pi-stacking interaction energy and, consequently, at least tricationic systems are required to fully uncouple the pi-stacked pyridine substituents.     

驱动X光二极管的级联Blumlein型脉冲网络过电压脉冲分析

为了提高装置容许的运行电压以提高辐射剂量产额,开展了放电过程中影响脉冲形成网络过电压幅值因素的研究。在引入开关导通不同步性和导通电阻条件下,建立了适用于任意电阻性负载的级联Blumlein型脉冲形成网络电压波过程理论模型,基于波过程模型进一步分析了影响脉冲形成网络过电压幅值的因素。研究表明开关不同步是产生过电压的主要因素,过电压峰值出现在开关闭合后的3倍形成网络电长度时刻。随着网络级联级数的增加,二极管阻抗与源阻抗匹配情况下最大过电压可达到-2倍充电电压,而二极管阻抗下降使得过电压幅值得以加强,阻抗过早崩溃可使过电压幅值接近充电电压的-3倍。     

Novel Bisthienylethene Containing Ferrocenyl‐Substituted Naphthalimide: A Photo‐ and Redox Multi‐Addressable Molecular Switch

A new photochromic bisthienylethene system (BTE? NAFc) is reported in which the ferrocene unit (Fc) is incorporated into a naphthalimide chromophore as the central ethene bridging unit. The incorporated Fc unit in the photochromic system of BTE? NAFc has several effects on optical properties, such as fluorescence‐modulation through photoinduced electron transfer (PET), a decrease in the photochromic cyclization quantum yield, and a selective two‐step oxidation process. The ability to drive ring‐opening and ring‐closing reactions with a secondary redox‐modulation provides increased functionality to the photochromic system. Based on these meaningful photo‐ and redox‐modulation properties, five unprecedented multi‐addressable states (BTE? NAFc, BTE? NAFc⁺, c‐BTE? NAFc, c‐BTE? NAFc⁺, and BTE⁺? NAFc⁺) and gated photochromism are successfully obtained within the unimolecular BTE platform, thus providing deeper insight into photochromic systems as multifunctional outputs.     

线型共轭Cx桥联双金属有机化合物

分子电子器件是近年来的一个热门课题。线型共轭Cx桥联双金属有机化合物是分子导线、分子开关等分子电子器件的模型化合物之一。本文介绍了线型共轭Cx桥联双金属有机化合物的结构、合成及光电性质。     

介质壁加速器用固态脉冲形成线设计与实验

设计和研制了一种CaO-TiO2-Al2O3复合陶瓷平板固态脉冲形成线,以期用于介质壁加速器。该脉冲形成线的几何参数为：陶瓷介质长度300 mm,宽度15 mm,厚度1 mm;银电极长度280 mm,宽度2 mm。电性能参数为：相对介电常数约23.5,特征阻抗约26 ,电长度约4.5 ns,直流耐压场强大于20 kV/mm,在s量级上升时间的脉冲电压下绝缘强度大于25 kV/mm。该固态脉冲形成线设计兼顾了光导开关的使用要求、高梯度绝缘子的设计指标、带电粒子束的输运及加速器的结构设计要求。结合GaAs光导开关,开展了固态Blumlein脉冲形成线实验研究工作,在脉冲充电电压约25 kV的条件下,固态Blumlein脉冲形成线实现脉冲电压输出约23 kV。     

光导开关非线性导通时的载流子累加效应

利用半导体激光器作为触发源,对砷化镓光导开关进行了实验研究,重点研究了载流子累加效应对开关输出特性的影响。实验结果表明,光导开关的导通机制与内部载流子数的多少直接相关,当开关中的载流子数积累到雪崩碰撞电离条件,开关就会发生非线性导通。采用低能量光脉冲序列触发光导开关,获得了高功率输出,降低了开关非线性导通时的触发光能和偏置电压,对于光导开关的应用具有重要意义。     

轨道式多间隙气体开关设计与性能测试

针对直线脉冲变压器对低电感、低抖动气体开关的研制需要,采用垂直布放的平板轨道电极,组成具有通视结构的水平间隙,设计了一种多间隙轨道式气体开关。利用Meek击穿判据计算了单间隙自击穿电压,实测了4个单间隙的自击穿电压及其相对标准偏差,并根据单间隙自击穿电压,利用概率分析方法预测了多间隙开关自击穿电压,计算值与实测结果一致。研究表明:开关电感最大约109 nH,自击穿电压相对标准偏差为1.5%,在60 kV触发电压和48%~74%欠压比下,开关抖动0.9~2.6 ns。与圆环形电极的多间隙气体开关相比,多间隙轨道式气体开关自击穿电压更稳定,也更容易触发。