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11.
The mechanism of the carbon-nitrogen coupling reaction of 2-iodo-selenophene with benzamide catalyzed by CuI has been investigated with density functional theory at the GGA/PW91/DND and GGA/PBE/DNP levels. The geometric configurations of the reactants, intermediates, transition states, and products were optimized and verified by means of vibration frequency calculations. A four-step mechanism was proposed for the reaction. The first step was the rate-control step. Two possible pathways in the fourth step were investigated, and the main pathway was identified by comparing their activation and dissociation energies. For comparison, the same calculations were performed to the reaction without the CuI activator. The activation barrier with CuI is 76 kJ mol(-1) smaller than that without CuI. It turns out that CuI can promote the reaction by lowering the activation energy. Our calculations reveal the crucial role of CuI in the reaction and agree well with experimental findings. 相似文献
12.
梁树权是中国科学院院士,是我国著名分析化学家。他从事分析化学研究与教育70余年,为我国分析化学的开拓和发展做出了重大贡献。通过展示梁树权先生完整的履历,以及他杰出的科研工作,以此纪念先生逝世十周年,致以缅怀之情。 相似文献
13.
Chun Huang Chang-Gua Zhen Siew Ping Su Zhi-Kuan Chen Xiao Liu De-Chun Zou Yan-Rong Shi Kian Ping Loh 《Journal of organometallic chemistry》2009,694(9-10):1317-1324
We report the synthesis and electrophosphorescent behavior of a series of novel iridium complex materials (Complexes A–F), which are composed of ligands bearing polyphenylphenyl dendron groups and acetylacetonate. Yellow to saturated red organic light-emitting diodes (OLEDs) based on these newly developed Ir complexes were fabricated through solution process by doping the complex materials into polyvinyl carbazole (PVK)/2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) matrices. The emission wavelengths of the materials could be effectively tuned from 549 nm to 640 nm by changing the conjugation of the ligands either through incorporating additional aromatic segment (e.g. phenyl or fluorenyl group) onto the basic dendron ligand or fusing two of the phenyl rings on the polyphenylphenyl dendron group. High performance devices with the configuration of ITO/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) (50 nm)/PVK:PBD (40%):Ir complex (6%) (70 nm)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) (12 nm)/Alq3 (20 nm)/Mg:Ag (150 nm) have been demonstrated. For example, when Complex B was used as the emissive layer, maximum current efficiency of 34.0 cd/A and external quantum efficiency of 10.3% have been achieved. When 1,3,5-tris(N-phenylbenzimidazol-2-yl) benzene (TPBI) was used as the block layer, the efficiencies can be further improved to 46.3 cd/A and 13.9%, respectively. These solution processed OLED devices demonstrated quite stable EL efficiencies over a large range of current density, which indicated that triplet–triplet annihilation in electrophosphorescence could be effectively suppressed by incorporation of the polyphenylphenyl dendron structure into iridium complexes. 相似文献
14.
A new manganese-based single-molecule magnet with a record-high antiferromagnetic phase transition temperature 下载免费PDF全文
We perform both dc and ac magnetic measurements on the single crystal of Mn30(Et-sao)3(C104)(MeOH)3 single- molecule magnet (SMM) when the sample is preserved in air for different durations. We find that, during the oxidation process, the sample develops into another SMM with a smaller anisotropy energy barrier and a stronger antiferromagnetic intermolecular exchange interaction. The antiferromagnetic transition temperature observed at 6.65 K in the new SMM is record-high for the antiferromagnetic phase transition in all the known SMMs. Compared to the original SMM, the only apparent change for the new SMM is that each molecule has lost three methyl groups as revealed by four-circle x-ray diffraction (XRD), which is thought to be the origin of the stronger antiferromagnetic intermolecular exchange interaction. 相似文献
15.
研究了AlGaN/GaN 高电子迁移率晶体管(HEMT)的质子辐照效应. 在3 MeV质子辐照下, 当辐照剂量达到1× 1015 protons/cm2时, 漏极饱和电流下降了20%, 最大跨导降低了5%. 随着剂量增加, 阈值电压向正向漂移, 栅泄露电流增加. 在相同辐照剂量下, 1.8 MeV质子辐照要比3 MeV质子辐照退化严重. 从SRIM软件仿真中得到不同能量质子在AlGaN/GaN异质结中的辐射损伤区, 以及在一定深度形成的空位密度. 结合变频C-V测试结果进行分析, 表明了质子辐照引入空位缺陷可能是AlGaN/GaN HEMT器件电学特性退化的主要原因. 相似文献
16.
Study on the drain bias effect on negative bias temperature instability degradation of an ultra-short p-channel metal-oxide-semiconductor field-effect transistor 下载免费PDF全文
This paper studies the effect of drain bias on
ultra-short p-channel metal-oxide-semiconductor field-effect
transistor (PMOSFET) degradation during negative bias temperature
(NBT) stress. When a relatively large gate voltage is applied, the
degradation magnitude is much more than the drain voltage which is
the same as the gate voltage supplied, and the time exponent gets
larger than that of the NBT instability (NBTI). With decreasing
drain voltage, the degradation magnitude and the time exponent all
get smaller. At some values of the drain voltage, the degradation
magnitude is even smaller than that of NBTI, and when the drain
voltage gets small enough, the exhibition of degradation becomes
very similar to the NBTI degradation. When a relatively large drain
voltage is applied, with decreasing gate voltage, the
degradation magnitude gets smaller. However, the time exponent
becomes larger. With the help of electric field simulation, this
paper concludes that the degradation magnitude is determined by the
vertical electric field of the oxide, the amount of hot holes
generated by the strong channel lateral electric field at the
gate/drain overlap region, and the time exponent is mainly
controlled by localized damage caused by the lateral electric
field of the oxide in the gate/drain overlap region where hot carriers
are produced. 相似文献
17.
Taking the actual operating condition of complementary metal oxide
semiconductor (CMOS) circuit into account, conventional direct
current (DC) stress study on negative bias temperature instability
(NBTI) neglects the detrapping of oxide positive charges and the
recovery of interface states under the `low' state of p-channel metal
oxide semiconductor field effect transistors (MOSFETs) inverter
operation. In this paper we have studied the degradation and recovery
of NBTI under alternating stress, and presented a possible recovery
mechanism. The three stages of recovery mechanism under positive bias
are fast recovery, slow recovery and recovery saturation. 相似文献
18.
构建了一个ZnO沉积在α-Al2O3(0001)表面生长初期的模型,采用基于密度泛函理论的平面波超软赝势法进行了动力学模拟.发现在400,600和800℃的条件下界面原子有不同的扩散能力,因此温度对ZnO/α-Al2O3(0001)表面界面结构以及ZnO薄膜生长初期模式有决定性的影响.在整个ZnO吸附生长过程中,O原子的扩散系数大于Zn原子的扩散系数,O原子的层间扩散对薄膜的均匀生长起着重要作用.进一步从理论计算上证实了ZnO在蓝宝石(0001)上两种生长模式的存在,400℃左右生长模式主要是Zn螺旋扭曲生长,具有Zn六角平面对称特征,且有利于Zn原子位于最外表面.600℃左右呈现为比较规则的层状生长,且有利于O原子位于最外表面.模拟观察到在ZnO薄膜临近Al2O3基片表面处,Zn的空位缺陷明显多于O的空位缺陷.
关键词:
扩散
薄膜生长
2O3(0001)')" href="#">α-Al2O3(0001)
ZnO 相似文献
19.
Enhanced electricity production from microbial fuel cells with plasma-modified carbon paper anode 总被引:1,自引:0,他引:1
He YR Xiao X Li WW Sheng GP Yan FF Yu HQ Yuan H Wu LJ 《Physical chemistry chemical physics : PCCP》2012,14(28):9966-9971
Microbial fuel cells (MFC) provide a new opportunity for simultaneous electricity generation and waste treatment. An improvement in the anode capacity of MFCs is essential for their scale-up and commercialization. In this work we demonstrate, for the first time, that plasma-based ion implantation could be used as an effective approach to modify carbon paper as an anode for MFC to improve its electricity-generating capacity. After the N(+) ion implantation, a decreased charge-transfer resistance is achieved, which is attributed to the increased C-N bonds after N(+) ion implantation. In addition, the surface roughness and hydrophobicity are also changed, which favor microbial adhesion on the anode surface. The cyclic voltammetry results show that both the electrochemical activity and the electron transfer are enhanced remarkably, leading to better MFC performance compared to the control. Such a plasma surface modification technique provides an effective way to modify the electrode for enhancing MFC performance for power generation. 相似文献
20.
采用射频磁控溅射技术在Pt/Ti/SiO2/Si(100)衬底上生长了掺镧钛酸铅(PLT)铁电薄膜.用X射线衍射技术(XRD)研究了PLT薄膜结晶性能,结果表明PLT薄膜为(111)择优取向钙钛矿相织构.使用原子力显微镜(AFM)和压电响应力显微镜(PFM)分别观察了PLT薄膜的表面形貌和对应区域的电畴结构.PFM观察显示PLT薄膜中存在90°纳米带状畴,电畴的极化为首尾相接的低能量的排列方式,带状畴的宽度为20-60nm.研究了PLT10铁电薄膜的制备条件与性能之间的关系.发现在优化条件下制备的PLT10铁电薄膜的介电常数εr为365、介电损耗tgδ为0.02,热释电系数γ为2.18×10-8C·(cm2·K)-1,可以满足制备非制冷红外探测器的需要. 相似文献