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41.
X. Z. Wang D. H. Zhang H. Q. Zheng S. F. Yoon C. H. Kam W. Shi A. Raman 《Journal of Crystal Growth》2000,210(4):458-462
We report the growth and characterization of GaInAsP films on GaAs substrates by solid source molecular beam epitaxy (SSMBE) using a valve phosphorous cracker cell at varied white phosphorous beam equivalent pressure (BEP). It is found that the GaInAsP/GaAs can be easily grown with the solid sources, and the incorporated phosphorous composition as a function of the beam equivalent pressure ratio, R=fP/(fP+fAs), can be well described by a parabolic relationship. With the increase of the incorporated phosphorous composition, the GaP-, InP-, InAs- and GaAs-like phonon modes shift towards opposite directions and their emission intensities also change. The first three modes shift to larger wave numbers while the last one shifts to smaller wave number. The lattice mismatch, Δa/a, of the materials grown with varied phosphorous BEP follows a linear relationship. Photoluminescence (PL) measurements reveal that as the phosphorous BEP ratio increases, the peak position or energy band gap of the material shifts towards higher energy; the full-width at half-maximum (FWHM) becomes narrower, and the luminescence intensity becomes higher. In addition, the materials also show smooth surfaces that do not change significantly with phosphorous beam equivalent pressure. 相似文献
42.
采用密度函数理论的B3LYP交换关联能泛函在6-311+G(2df,2p)基组水平上,优化计算了Ca+,Mg+与RNA碱基嘧啶各同分异构体形成稳定复合物的结构,发现其中C1M,T1M和U1M(M=Ca+和Mg+)为最稳定复合物,并对这些复合物红外振动进行了计算.计算结果显示碱基嘧啶单体主要存在的两个红外特征振动,是由环振动和环外氧原子及与其成键的环上碳原子之间产生伸缩振动引起的.当形成复合物时,由于离子的参与,使单体碱基分子的振动情况发生了改变,主要表现在离子倾向于与环外负电子原子N和O原子成键,使与离子直接作用环外原子参与的特征振动频率减小,谱线红移;不与离子直接作用环外原子引起的特征振动频率增大,谱线蓝移. 相似文献
43.
44.
G. W. Arnold 《辐射效应与固体损伤》2013,168(1-4):15-19
A new method of producing a glass-ceramic surface layer on fused silica has been demonstrated using Li+-ion implantation and relatively low-temperature annealing. Infrared reflection spectroscopy (IRS) was used to study the effects of ion implantation on structural changes. Isochronal annealing of samples implanted with 250 keV Li+/cm2 brings about a dramatic change in the IRS spectra at 800°C in that it becomes identical with that of α-quartz. The dependence of the degree of crystallization on temperature, Li+-ion fluence, and silica type was studied. 相似文献
45.
To extend the optical property characterization of metal–Cu2O polyhedra, 50 nm Au@Cu cubic cores are used to fabricate Au@Cu–Cu2O core–shell cubes, octahedra, and rhombic dodecahedra with tunable sizes. Despite the unusually large lattice mismatch of 15.1% between Cu and Cu2O, fine adjustment in the volumes of reagents introduced allows the formation of these heterostructures. To relieve the lattice strain, the metal cores are essentially never found to locate at the particle center, and slight lattice spacing shifts are recorded. Although efforts are made to reduce the heterostructure sizes, the Cu2O shells are generally too thick to reveal surface plasmon resonance (SPR) absorption band from the metal cores. Only the Au@Cu–Cu2O cubes with many cores located near the particle corners show observable SPR band red‐shift, but UV–vis spectra of all particle shapes are still dominated by Cu2O absorption and light scattering bands. Au@Cu–Cu2O cubes consistently show the most red‐shifted absorption bands than those of octahedra resulting from the optical facet effects. 相似文献
46.
时间延迟积分型面阵CMOS图像传感器MTF速度失配模型研究 总被引:1,自引:2,他引:1
研究了时间延迟积分型面阵互补金属氧化物半导体(CMOS)图像传感器调制传递函数(MTF)速度失配特性,在分析累加级数、像素尺寸、镜头放大倍数、行周期及电机运动速度失配等影响因素的基础上,建立了MTF速度失配模型。基于现场可编程门阵列(FPGA)开发板,搭建面阵CMOS图像传感器实现线阵时间延时积分(TDI)的CMOS测试系统。实验结果表明,在光强为3lx,速度失配M(ΔV/V)<2,8级时间延迟积分与面阵成像相比,MTF值提高50%;当累加级数为8级,速度失配满足M(ΔV/V)=2的速度失配容限时,奈奎斯特频率处的MTF值下降10%,当速度失配达到M(ΔV/V)=10时,MTF值下降35%。 相似文献
47.
48.
Mitsuaki Yano Isao Makabe Kazuto Koike 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):449
This report describes photoluminescence (PL) properties of PbTe/CdTe single quantum wells grown on (1 0 0)-oriented GaAs substrates by molecular beam epitaxy. Despite the differences in crystal structure and thermal expansion coefficient between PbTe and CdTe, an intense mid-infrared emission was observed even at higher temperatures than 300 K. Multiple peaks, however, were found in the PL spectra, and the analysis of the PL peak energy dependence on temperature revealed an important role of the thermal mismatch. 相似文献
49.
DNA中的胞嘧啶在化学致变剂作用下会发生脱氨反应,被认为是导致基因损伤的重要原因之一,本文采用毛细管电泳测定胞嘧啶和尿嘧啶,并将此种新方法用于过氧化氢存在下胞嘧啶脱氨反应的动力学研究,结果显示该反应对过氧化氢和胞嘧啶均为一级反应,反应活化能为70.35kJ.mol^-1,明显低于自发脱氨反应,表明过氧化氢可以加速胞嘧啶脱氨反应。 相似文献
50.
Summary Treatment of 2-formyl-3-dimethylamino-propenenitrile (1a) and 2-ethoxycarbonyl-3-dimethylamino-propenenitrile (1b), resp., with substituted ureas led to the 2-cyano-3-ureidoacrylates2, which can be cyclized under alkaline conditions to give 5-formyl-5-cyano-, and 5-alkoxycarbonyl-2-oxopyrimidine derivatives3,6, and7. Reaction of3 with isopentylnitrite gave a mixture of the deaminated and oxidized product4 and the oxo derivative5, which was acetalized during the separation step. Similar reaction with the alkoxycarbonyl derivatives7 led to the formation of 1-alkyl-5-alkoxycarbonyl-pyrimidine-2,6-diones8a–d.
Synthesen mit Nitrilen, 95. Mitt.: Deaminierung von Cytosinderivaten
Zusammenfassung Die Reaktion von 2-Formyl-3-dimethylamino-propennitril (1a) und 2-Ethoxycarbonyl-3-dimethylamino-propennitril (1b) mit substituierten Harnstoffen führte zur Bildung der 2-Cyan-3-ureidoacrlate2, welche unter alkalischen Bedingungen zu den 5-Formyl-, 5-Cyan- oder 5-Alkoxycarbonyl-2-oxopyrimidinen3,6 bzw.7 cyclisiert werden konnten. Reaktion von3 mit Isopentylnitrit ergab eine Mischung aus deaminiertem und zugleich oxidiertem Produkt4 sowie dem Oxoderivat5, welches während der Säulentrennung auf Kieselgel zusätzlich acetalisiert worden war. Die ähnliche Reaktion mit den Alkoxycarbonyl-Derivativen7 führte zur Bildung der 1-Alkyl-5-alkoxycarbonyl-pyrimidin-2,6-dione8a–d.相似文献