Analysis of the breakdown mechanism for an ultra high voltage high-side thin layer silicon-on-insulator p-channel low-density metal-oxide semiconductor

This paper discusses the breakdown mechanism and proposes a new simulation and test method of breakdown voltage(BV) for an ultra-high-voltage(UHV) high-side thin layer silicon-on-insulator(SOI) p-channel lateral double-diffused metal-oxide semiconductor(LDMOS).Compared with the conventional simulation method,the new one is more accordant with the actual conditions of a device that can be used in the high voltage circuit.The BV of the SOI p-channel LDMOS can be properly represented and the effect of reduced bulk field can be revealed by employing the new simulation method.Simulation results show that the off-state(on-state) BV of the SOI p-channel LDMOS can reach 741(620) V in the 3-μm-thick buried oxide layer,50-μm-length drift region,and at 400 V back-gate voltage,enabling the device to be used in a 400 V UHV integrated circuit.     

Stereodivergent synthesis of enantioenriched azepino[3,4,5-cd]-indoles via cooperative Cu/Ir-catalyzed asymmetric allylic alkylation and intramolecular Friedel–Crafts reaction

The development of enantioselective annulation reactions using readily available substrates for the construction of structurally and stereochemically diverse heterocycles is a compelling topic in diversity-oriented synthesis. Herein, we report efficient catalytic asymmetric formal 1,3-dipolar (3 + 4) cycloadditions of azomethine ylides with 4-indolyl allylic carbonates for the construction of azepino[3,4,5-cd]-indoles fused with a challenging seven-membered N-heterocycle, a frequently occurring tricyclic indole scaffold in bioactive compounds and pharmaceuticals. Through cooperative Cu/Ir-catalyzed asymmetric allylic alkylation followed by intramolecular Friedel–Crafts reaction, an array of azepino[3,4,5-cd]-indoles were obtained in good yields with excellent diastereo-/enantioselective control. More importantly, the full stereodivergence of this transformation was established via synergistic catalysis followed by acid-promoted epimerization, and up to eight stereoisomers of the cycloadducts bearing three stereogenic centers could be predictably achieved from the same set of starting materials for the first time. Quantum mechanical computations established a plausible mechanism for the synergistic Cu/Ir catalysis to stereodivergently introduce two vicinal stereocenters whose stereochemical information is remotely delivered across the fused azepine ring to control the third chiral center. Epimerization of the last center involves protonation-enabled reversal of the thermodynamically controlled relative configuration.

A stereodivergent synthesis of azepino[3,4,5-cd]-indoles bearing three stereogenic centers was established via synergistic dual-metal catalysis followed by acid-promoted epimerization, and up to all eight stereoisomers could be predictably achieved.     

HIRFL人身安全联锁系统的设计与实现

兰州重离子加速器(简称HIRFL),是我国规模最大、加速离子种类最多、能量最高的重离子研究装置,可提供单核子能量达GeV量级的重离子束。HIRFL运行时,束流会在加速器隧道内产生辐射,需要建立一套人身安全联锁系统来保障人员的辐射安全。HIRFL人身安全联锁系统遵循分区联锁、硬件最可靠、失效保护、冗余及独立性、自锁等设计原则,选用了可靠性高的冗余PLC作为核心控制器,并使用了安全性高的联锁部件。本工作的完成保障了HIRFL工作人员的辐射安全,也为同类型加速器装置的人身安全联锁系统设计提供了参考。     

Mo/Si aperiodic multilayer broadband reflective mirror for 12.5-28.5-nm wavelength range

Aperiodic molybdenum/silicon (Mo/Si) multilayer designed as a broadband reflective mirror with mean reflectivity of 10% over a wide wavelength range of 12.5-28.5 nm at incidence angle of 5° is developed using a numerical optimized method. The multilayer is prepared using direct current magnetron sputtering technology. The reflectivity is measured using synchrotron radiation. The measured mean reflectivity is 7.0% in the design wavelength range of 12.5-28.5 nm. This multilayer broadband reflective mirror can be used in extreme ultraviolet measurements and will greatly simplify the experimental arrangements.     

一种新颖的高灵敏度光纤光栅带宽调谐机构

设计了一种由一直梁和两个半圆拱组成的开口环结构,并将均匀光纤布拉格光栅斜贴于直梁中间的表面处。对两半圆拱施加与直梁方向平行的应力作用时,光纤光栅受到线性应力场的作用,光纤布拉格光栅即转化为啁啾光纤光栅。该机构实现了光纤光栅带宽的线性调谐,线性度高达0．9982,实验结果与理论分析一致。与以往的带宽调谐机构相比,该机构具有很高的应力灵敏度,在20N力的作用下,可产生约7nm的带宽反射,灵敏度达0．34nm／N。利用环境温度对带宽调谐无影响的特性,采用带宽编码技术,研制出具有温度自动补偿特性、高灵敏度的带宽调谐装置。     

新型宽温区高热稳定性微波功率SiGe 异质结双极晶体管

宽温区大电流下的热不稳定性严重制约着功率SiGe 异质结双极晶体管 (HBT) 在射频和微波电路中的应用.为改善器件的热不稳定性, 本文利用SILVACO TCAD建立的多指功率SiGe HBT模型, 分析了器件纵向结构中基区Ge组分分布对微波功率SiGe HBT电学特性和热学特性的影响. 研究表明, 对于基区Ge组分为阶梯分布的HBT, 由于Ge组分缓变引入了少子加速电场, 使它与均匀基区Ge组分HBT相比, 具有更高的特征频率f_T, 且电流增益β和f_T随温度变化变弱, 这有利于防止器件在宽温区工作时电学特性的漂移.同时, 器件整体温度有所降低, 但器件各指温度分布均匀性较差.考虑多指HBT各发射极指散热能力存在差异, 在器件纵向结构设计为基区Ge组分阶梯分布的同时, 对其横向版图进行发射极指间距渐变结构设计, 用于改善器件各指温度分布的均匀性, 进而提高HBT的热稳定性.结果表明, 与基区Ge组分为均匀分布的等发射极指间距结构HBT相比, 新器件各指温度分布均匀性明显改善, f_T保持了较高的值, 且β和f_T 随温度变化不敏感, 热不稳定性得到显著改善, 显示了新器件在宽温区大电流下工作的优越性. 关键词： SiGe 异质结双极晶体管 Ge组分分布 发射极指间距渐变技术 热稳定性     

The relation between the radii and the densities of magnetic skyrmions

Compared with the traditional magnetic bubble, a skyrmion has a smaller size, and better stability and therefore is considered as a very promising candidate for future memory devices. When skyrmions are manipulated, erased and created, the density of skyrmions can be varied, however the relationship between the radii and the densities of skyrmions needs more exploration. In this paper, we study this problem both theoretically and by using the lattice simulation. The average radius of skyrmions as a function of material parameters, the strength of the external magnetic field and the density of skyrmions is obtained and verified. With this explicit function, the skyrmion radius can be easily predicted, which is helpful for the future study of skyrmion memory devices.     

基于数学形态学的表面原子熔融相的 STM图像识别算法

高温扫描隧道显微镜(HT-STM)可以实时原位地捕捉到表面原子的熔化相变过程.在这一原位变温实验中,快速可靠地识别出每帧STM图像中的熔融相十分关键.传统的手工统计方法存在效率低下、随意性大等问题.我们发展出一套基于数学形态学的算法,来自动快速地识别.与人工方法相比,该算法消除了人为主观误差,使确定的边界更加准确、光滑,处理效率提高了266倍.     

HL-2M 装置运行控制技术初步研究

重点介绍了 HL-2M 装置的运行技术和初步的等离子体控制实验结果,包括等离子体放电方案设计、 线圈电流控制、击穿阶段零场匹配和等离子体电流以及位移的控制。为了降低放电运行风险,HL-2M 装置初始放 电采用了简化的放电方案,通过整定 PID 参数实现了线圈电流控制,在击穿阶段获得了 10V 以上的环电压和较大 范围的零场区域,成功实现等离子体击穿。最后,投入了等离子体电流和水平位移反馈控制算法,成功将等离子 体放电脉宽提升至 200ms 以上,且维持 I_p≥100kA 的时间超过了 100ms,上述结果表明 HL-2M 装置运行控制技术 得到了初步的检验。      

Pt/C催化剂中纳米Pt颗粒团聚效应的小角X射线散射

 应用小角X射线散射(SAXS)技术,对乙二醇合成法、浸渍还原法和微波加热法制备的Pt/C催化剂粉体内纳米Pt颗粒的团聚效应进行了研究,得到了不同方法制备的Pt颗粒及其团聚体的特征尺寸、体积分布、表面积变化、团聚程度等信息,并利用透射电镜（TEM）对3种样品进行了测试。实验结果表明:微波加热法制备的催化剂中,Pt颗粒较好地分散于C载体上,且Pt颗粒具有尺度小、分布范围窄、总表面积大和团聚体较少等特征;常规浸渍和乙二醇还原两种方法制备的催化剂中Pt颗粒大小分布相似,但乙二醇还原法制备的催化剂总表面积和团聚体尺度更大,数量也更多。