Microscopy of pentacene thin films

Thin films of pentacene were deposited by vacuum sublimation onto amorphous carbon, glass, silicon and mica substrates, then characterized by X-ray and electron diffraction, transmission electron microscopy (TEM) and atomic-force microscopy (AFM). Sub-monolayer films consist of dendritic islands, which change to more compact fractal shapes upon transforming to a multilayer structure (with decrease in surface area) prior to complete coverage of the substrate. Increased crystallite size was obtained by heating the substrate during deposition and by post-deposition annealing. Irradiation with 200-keV electrons was found to destroy the crystallinity of the films after a dose of 0.6?C/cm² (or 2?C/cm² if the specimen is cooled to 90?K during TEM observation). We argue that, despite this moderate radiation sensitivity, TEM under near-optimal conditions can image monolayers of pentacene with sub-nm resolution.     

GaN FP-HEMTs中击穿电压与电流崩塌的关系

研究了钝化在抑制电流崩塌的同时，会引起HEMT器件击穿电压的下降.而采用场板结构的AlGaN/GaN场板HEMT器件(FP-HEMT)的击穿电压从46V提高到了148V，表明了场板对提高击穿电压有显著作用(3倍以上).接着，比较了FP-HEMT器件与常规HEMT器件，钝化后HEMT器件在应力前后的电流崩塌程度，得出了采用场板结构比之钝化对器件抑制电流崩塌有更明显作用的结论.从理论上和实验上都表明，采用场板结构能够很好解决提高击穿电压与抑制电流崩塌之间的矛盾. 关键词： GaN 场板 击穿电压 电流崩塌     

四氯苯醌与嘧啶类核酸碱基的光化学氢抽取和电子转移反应

采用纳秒时间分辨的激光闪光光解实验技术,研究了四氯苯醌(TCBQ)分子与两种嘧啶核酸碱基(胸腺嘧啶和尿嘧啶)分子在355nm激发下的光化学反应动力学. 355 nm将TCBQ分子布居到激发三重态³TCBQ^*,高反应活性的³TCBQ^*与碱基分子发生两个平行的反应,氢抽取反应和电子转移反应,分别对应生成瞬态光谱上观测到的两个光反应产物TCBQH·和TCBQ·^-. 这两个反应同时生成的碱基自由基和碱基阳     

应用于扫描探针显微镜的石英音叉机械模型研究

石英音叉作为力传感器广泛地应用于各种扫描探针显微镜,主要涉及石英音叉的同相振动和反相振动两种振动模式.通过实验方法和有限元仿真方法对石英音叉的两种振动模式进行研究,发现石英音叉的双臂之间以及双臂与音叉的基部之间都存在耦合作用,双臂之间的耦合使音叉的反相共振频率升高,双臂与基部之间的耦合使音叉的同相共振频率降低.针对两种振动模式的动态特性建立了石英音叉的机械模型并进行合理简化.简化模型是一个四弹簧三质点系统,计算了简化模型的参数.通过一个音叉臂等效质量变化与音叉反相共振频率变化之间的定量关系证明了简化机械模 关键词： 扫描探针显微镜 石英音叉 振动模式 机械模型     

Size-refinement enhanced flexibility and electrochemical performance of MXene electrodes for flexible waterproof supercapacitors

Increasing mechanical flexibility without sacrificing electrochemical performance of the electrode mate-rial is highly desired in the design of flexible electro...     

基于无人机高光谱特征参数和株高估算马铃薯地上生物量

地上生物量(above-ground biomass,AGB)是评价作物长势及其产量估测的重要指标,对指导农业管理具有重要的作用.因此,快速准确地获取生物量信息,对于监测马铃薯生长状况,提高产量具有重要的意义.于马铃薯现蕾期、块茎形成期、块茎增长期、淀粉积累期、成熟期获取成像高光谱影像、实测株高(heigh,H)、地上...     

重频XeF蓝绿激光技术

 利用表面放电光泵浦技术,研制了重频XeF(C-A)激光器,运行频率达到10 Hz。研究了运行频率、气体流量对激光输出能量稳定性的影响,分析了影响输出稳定性的主要因素,实验结果表明,提高气流量可有效改善重频输出能量的稳定性。同时,还给出了优化实验条件下不同运行频率连续20个脉冲较为理想的输出结果。运行频率分别为1,2,5 Hz时,输出能量稳定性较好,输出能量大于4.0 J;气流量大于53 L/s时,10 Hz重频运行的输出稳定性已显著提高,平均输出能量也达到1.8 J。     

Application of alkoxide in catalytic transfer hydrogenation of unsaturated nitrogen compounds

Alcoholate was utilized in catalytic transfer hydrogenation of unsaturated nitrogen compounds. In the reduction of nitro compounds, oximes and imines, alkoxide was used as the promoter, with alcohol as the hydrogen source, while in the reduction of nitriles, alkoxide was used as the hydrogen source.