2,2,6,6-四甲基哌啶氧铵盐与吩噻嗪类化合物单电子转移反应动力学——Marcus理论的应用

2 ,2 ,6 ,6 四甲基哌啶氧铵盐 ( 1a ,1b)与吩噻嗪类化合物 ( 2a～ 2g)迅速反应 ,生成相应的氮氧自由基 ( 3a ,3b)和吩噻嗪类化合物的正离子自由基 ( 4a～ 4g) .通过EPR和NMR的谱线增宽效应 ,测定了乙腈中 1和 3以及 2和 4之间的电子自交换反应速率常数 ,应用Marcus理论研究了 1和 2之间的反应动力学     

高比探测率和高速石墨烯/n-GaAs复合结构的光电探测器

混合结构的石墨烯/半导体光电晶体管因其超高的响应度而备受关注.然而,该类光电晶体管通过源-漏电极测试得到的比探测率(D．)容易受到1/f噪声的限制.本文制备了混合结构的石墨烯/GaAs光电探测器,通过源-栅电极测得D*大约为1.82X1011 Jones,与通过源-漏电极测量相比,D'提高了约500倍.这可归因于界面上...     

Integration of GaN thin films with silicon substrates by fusion bonding and laser lift-off

GaN thin films grown on sapphire substrates by metalorganic chemical vapor deposition (MOCVD) are successfully bonded and transferred onto Si receptor substrates using fusion bonding and laser lift-off (LLO) technique. GaN/Al_2O_3 structures are joined to Si substrates by pressure bonding Ti/Au coated GaN surface onto Ti/Au coated Si receptor substrates at the temperature of 400℃. KrF excimer laser with 400-mJ/cm~2 energy density, 248-nm wavelength, and 30-ns pulse width is used to irradiate the wafer through the transparent sapphire substrates and separate GaN films from sapphire. Cross-section scanning electron microscopy (SEM) combined with energy dispersive X-ray spectrometer (EDS) measurements show that Au/Si solid solution is formed during bonding process. Atomic force microscopy (AFM) and photoluminescence (PL) measurements show that the qualities of GaN films on Si substrates degrade little after substrates transfer.     

基于分数导数研究高强度聚焦超声的非线性声场

在高强度聚焦超声(high intensity focused ultrasound, HIFU) 的研究中, 生物组织的衰减和色散性质会对声能量的空间分布产生影响. 本文提出应用分数导数修正非线性Khokhlov-Zabolotskaya-Kuznetsov (KZK)方程, 研究生物组织中非线性HIFU声场. 对三种生物仿体的衰减和声速色散的理论实验研究表明分数导数应用的可行性, 在此基础上通过数值仿真分析研究了衰减及声速随频率的变化对HIFU焦域分布的影响. 研究结果表明, 在计算强非线性聚焦超声时, 由于高次谐波的强色散作用, 引入分数导数来解决生物组织特殊的衰减以及色散问题可进一步提高HIFU治疗的安全性. 关键词： 分数导数 声衰减 色散 高强度聚焦超声     

A low-threshold and high-power oxide-confined 850-nm AlInGaAs strained quantum-well vertical-cavity surface-emitting laser

A low-threshold and high-power oxide-confined 850-nm AlInGaAs strained quantum-well (QW) vertical-cavity surface-emitting laser (VCSEL) based on an intra-cavity contacted structure is fabricated. A threshold current of 1.5 mA for a 22 μm oxide aperture device is achieved, which corresponds to a threshold current density of 0.395 kA/cm². The peak output optical power reaches 17.5 mW at an injection current of 30 mA at room temperature under pulsed operation. While under continuous-wave (CW) operation, the maximum power attains 10.5 mW. Such a device demonstrates a high characteristic temperature of 327 K within a temperature range from -12℃ to 96℃ and good reliability under a lifetime test. There is almost no decrease of the optical power when the device operates at a current of 5 mA at room temperature under the CW injection current.     

采用BCB平整技术的高速850 nm垂直面发射激光器

垂直腔面发射激光器因其具有低阈值、低功耗、可实现高速调制等优势,广泛地应用于光通信和光互连等领域。寄生电容是影响激光器的调制带宽的主要因素之一。本文通过采用低k值的苯并环丁烯（BCB）平整技术有效地降低了垂直腔面发射激光器的寄生电容。详细研究了BCB平整技术的最优工艺参数,为未来高速垂直腔面发射激光器的制造技术提供参考。低k值BCB平整垂直腔面发射激光器在7 μm氧化孔径下3 dB小信号调制带宽可达15.2 GHz。     

采用BCB平整技术的高速850nm垂直面发射激光器（英文）

垂直腔面发射激光器因其具有低阈值、低功耗、可实现高速调制等优势,广泛地应用于光通信和光互连等领域。寄生电容是影响激光器的调制带宽的主要因素之一。本文通过采用低k值的苯并环丁烯(BCB)平整技术有效地降低了垂直腔面发射激光器的寄生电容。详细研究了BCB平整技术的最优工艺参数,为未来高速垂直腔面发射激光器的制造技术提供参考。低k值BCB平整垂直腔面发射激光器在7μm氧化孔径下3 d B小信号调制带宽可达15.2 GHz。     

Scalability of dark current in silicon PIN photodiode

The mechanism for electrical conduction is investigated by the dark temperature-dependent current–voltage characteristics of Si PIN photodiodes with different photosensitive areas.The characteristic tunneling energy E_(00) can be obtained to be 1.40 me V,1.53 me V,1.74 me V,1.87 me V,and 2.01 me V,respectively,for the photodiodes with L = 0.25 mm,0.5 mm,1 mm,1.5 mm,and 2 mm by fitting the ideality factor n versus temperature curves according to the tunneling-enhanced recombination mechanism.The trap-assisted tunneling-enhanced recombination in the i-layer plays an important role in our device,which is consistent with the experimental result that area-dependent leakage current is dominant with the side length larger than 1 mm of the photosensitive area.Our results reveal that the quality of the bulk material plays an important role in the electrical conduction mechanism of the devices with the side length larger than 1 mm of the photosensitive area.     

临近空间大气环境研究现状

临近空间指高度位于(20$\sim$100)\,km之间的地球大气层.简要综述临近空间的已有了解和研究前沿,包括基本状态、主要过程与控制因子.介绍了基于已有探测资料的经验模式的建立和基于基本物理定量规律和数值模拟方法的中层大气环流和化学气候数值模拟.最后从临近空间大气环境保障应用角度提出研究的新建议.      

吩噻嗪在十二烷基硫酸钠/苯甲醇/水微乳液中的定位

采用循环伏安法和荧光猝灭法研究了吩噻嗪（PTZ）在十二烷基硫酸钠（SDS）/苯甲醇（BA ）/ 水（H2O）微乳液中的定位.结果表明,吩噻嗪在十二烷基硫酸钠/苯甲醇/水体系微乳液中位于微乳液膜相中靠近表面活性剂极性头基的一侧,PTZ分子中的S原子和N原子均可朝向表面活性剂的极性头基.