Fluorine-plasma treated AlGaN/GaN high electronic mobility transistors under off-state overdrive stress

Influences of off-state overdrive stress on the fluorine-plasma treated AlGaN/GaN high-electronic mobility transistors (HEMTs) are experimentally investigated. It is observed that the reverse leakage current between the gate and source decreases after the off-state stress, whereas the current between the gate and drain increases. By analyzing those changes of the reverse currents based on the Frenkel-Poole model, we realize that the ionization of fluorine ions occurs during the off-state stress. Furthermore, threshold voltage degradation is also observed after the off-state stress, but the degradations of AlGaN/GaN HEMTs treated with different F-plasma RF powers are different. By comparing the differences between those devices, we find that the F-ions incorporated in the GaN buffer layer play an important role in averting degradation. Lastly, suggestions to obtain a more stable fluorine-plasma treated AlGaN/GaN HEMT are put forwarded.     

Watt-level,green-pumped optical parametric oscillator based on periodically poled potassium titanyl phosphate with high extraction efficiency

We report a compact, efficient optical parametric oscillator (OPO) based on a periodically poled potassium titanyl phosphate (PPKTP) crystal pumped by a 532 nm laser, which generated 1.51 W of average power at the signal wavelength of 709 nm with the pulse duration of ～ 1.0 ns. The extraction efficiency was up to 59%. To the best of our knowledge, this is the first report on Watt-level green-pumped PPKTP-based singly resonant oscillator OPO (SRO-OPO). The precise build-up time of OPO was determined to be 1.6 ns benefitting from the characteristic of twin-peak pulse profile of pump beam. The spectrum width of the idler was also measured to be 4.2 nm with the central wavelength of 2134 nm at 0.2 nm spectral resolution of optical spectrum analyzer. In addition, the beam quality of M² < 1.9 of generated signal exhibits a good consistency with M² < 1.5 for the pump source.     

新型2-羟乙基苯并[d]异噻唑-3(2H)-酮脂肪酸酯的合成及其抑菌活性

以苯并[d]异噻唑-3(2H)-酮为原料,通过取代与酯化反应合成了9个未见文献报道的了2-{3-氧代苯并[d]异噻唑-2(3H)-基}乙醇脂肪酸酯(4a～4i),其结构经1H NMR,IR和元素分析表征。初步体外抑菌活性测试结果表明,4对六种实验菌均表现出不同程度的抑菌活性,尤其对革兰氏阳性菌,用药量32μg.mL-1时抑菌率在90%以上。     

苯并异噻唑啉酮类化合物的合成与活性研究

通过烷基醇与固体三光气(BTC)反应后加入1,2-苯并异噻唑啉-2(3H)-酮(BIT)继续反应的“一锅法”制备了8种未见文献报道的2-(苯并异噻唑啉-3-酮-2-基)甲酸酯类化合物.化合物结构经IR、1HNMR和元素分析确认,并且对枯草芽孢杆菌、金黄色葡萄球菌、嗜水单细胞菌和大肠杆菌进行了初步抑菌活性实验,实验结果表...     

ITO上AuPd合金和Au阵列图案的制备及电催化活性的SECM表征

利用电化学湿法印章技术在氧化铟锡(ITO)导电玻璃上制备AuPd合金和Au的双组分阵列图案.采用具有微浮雕图案的琼脂糖印章存储足够多的溶液,并通过控制电沉积的时间来控制图案厚度.应用场发射扫描电子显微镜(FE-SEM),X射线能谱分析(EDX)和原子力显微镜(AFM)分别对ITO表面上的AuPd合金和Au的形貌和组分进行表征,并通过循环伏安(CV)技术和扫描电化学显微镜(SECM)研究比较了Au和AuPd合金的催化活性.利用扫描电化学显微镜(SECM)的针尖产生-基底收集(TG-SC)模式和氧化还原竞争(RC)模式,发现Au电极对二茂铁甲醇氧化物(FcMeOH+)电催化还原能力高于AuPd合金电极,而在AuPd合金上催化还原H2O2的能力显著高于Au.     

磷系阻燃剂插层镁铝型水滑石复合物的制备及其在热塑性聚氨酯中的阻燃应用

采用直接的无溶剂制备方法,将3种磷系阻燃剂9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)、聚磷酸铵(APP)和三聚氰胺聚磷酸盐(MPP)分别插层到镁铝型水滑石(MAH)片层中,制备了3种含磷阻燃剂的MAH复合物(DOPO-MAH、APP-MAH和MPP-MAH),并采用模压成型法制备了MAH复合物与热塑性聚氨酯(TPU)的复合材料。采用X射线衍射、扫描电子显微镜和热重分析分别对复合物进行了表征,并且通过锥形量热仪对复合材料进行了表征。结果表明,MAH中MPP的分散性较差,DOPO和APP的分散性较好,并且磷元素分布均匀。MAH的初始层间距为4.11 nm,APP和MPP均在0.5 h时就已完成插层,最终层间距分别缩小到3.93和4.04 nm。DOPO则在0.5 h后完成,但插层后的层间距更小,为3.86 nm。与物理混合物所制得的复合材料相比,(DOPO-MAH-6h)/TPU和(APP-MAH-6h)/TPU的热释放速率峰值分别从669.3 kW/m²降至573.9 kW/m²,从657.7 kW/m²     

十二烷基硫酸钠辅助制备高电容性能多孔碳

本工作通过一步水浴法制备高氮/氧含量密胺树脂(MF),引入阴离子型表面活性剂十二烷基硫酸钠(SDS)改变聚合物的反应历程,使进入SDS胶束中的三聚氰胺与甲醛在盐酸催化条件下进行聚合反应,高温碳化后成功制备MF衍生多孔碳材料.对MF衍生多孔碳材料分别进行了扫描电镜、比表面积等表征,结果表明,其具有多孔互穿网络结构,比表面...     

双光子吸收碱金属蒸气激光器研究进展

蓝紫激光和中红外激光在基础研究和国防工程中有重要的应用前景。单光子吸收的碱金属蒸气激光器具有量子效率高、受激发射截面大和热管理性能好等优点,近些年来已成为激光领域中研究热点之一,目前已实现k W量级的输出。双光子吸收的碱金属蒸气激光器可实现蓝紫激光和中红外激光级联输出的特性,也引起越来越多的关注。本文从碱金属原子密度、泵浦光功率、偏振和频率失调量以及调控激光等几种影响因素出发,综述了双光子吸收碱金属蒸气激光的研究进展,在此基础上分析了影响激光输出特性的原因,最后对双光子吸收碱金属蒸气激光器的发展趋势进行了展望。     

不同条件下血氨浓度的变化及影响因素

为保证人体中血氨浓度检测结果的准确性,并分析其影响因素,利用美国强生Vitros 250型干化学分析仪,通过比色法对血氨浓度进行检测.对检测结果用统计学软件SPSS 13.0进行计算处理.结果显示:在其它条件一定的情况下,两种温度下血氨浓度的变化不同,随着存放时间的延长,血氨浓度增加.因此对血氨标本应及时送检,检测时间应不超过20min,如不能及时检测,最好放于2-8℃冰箱中保存,但保存时间不应超过2.5h.     

Electronic Instability of Kagome Metal CsV3Sb5 in the 2×2×2 Charge Density Wave State

Recently discovered kagome metals AV₃Sb₅(A = K,Rb,and Cs) provide an ideal platform to study the correlation among nontrivial band topology,unconventional charge density wave(CDW),and superconductivity.The evolution of electronic structures associated with the change of lattice modulations is crucial for understanding of the CDW mechanism,with the combination of angle-resolved photoemission spectroscopy(ARPES)measurements and density functional theory calculations,we invest...