氯化物体系气相外延镓铟砷

本文报告用Ga/InAs/AsCl_3/H_2体系,在GaAs衬底上气相外延Ga_(1_x)In_xAs的结果。通过生长过渡层,降低晶格失配;用水平舟生长的InAs源,并适当选择生长参数,得到表面光洁、完整性较好的外延层。组份x值在0.25以内,最佳电性为:     

不同参数的不对称阶梯型量子阱等离激元特性研究

用无规相近似的二子带模型,系统研究了阶梯层宽度、深阱宽度、阶梯层的Al组分(阶梯层势垒的高度)对Al Ga As/Ga As不对称阶梯型量子阱中准二维电子气的等离激元特性的影响。发现子带间等离激元模的能量大小取决于基态和第一激发态的能级差,而模的长短取决于这两个能级波函数的交叠大小。这些结论可能为研究空间不对称效应对准二维电子气特性的影响以及基于阶梯型量子阱结构的器件应用等方面提供有益的参考。     

全固源分子束外延1.55 μm波段应变补偿InAsP/InGaP多量子阱材料

利用新型全固源分子束外延技术，对1．55μm波段应变补偿InAsP，InGaP多量子阱材料的生长进行了研究。在InAsP阱和InGaP垒之间插入InP中间层以减小阱和垒之间较大的剪切力。通过对生长材料的x射线衍射摇摆曲线和室温光致荧光光谱的比较，优化生长参数，获得了高质量的InAaP/InP/InGaP/InP应变补偿多量子阱结构，阱、垒、中间层的厚度分别为7．1，6．0，1．9nm的7个周期的应变补偿多量子阱材料室温光荧光谱半高全宽为18．2meV，是当前文献报道的1．55μm波段的InAaP多量子阱材料的最好结果之一。     

离子束外延生长（Ga,Mn,As）化合物

利用质量分离的低能双离子束外延技术,得到了（Ga,Mn,As）化合物。补底温度523K条件下生长的样品的俄歇电子谱表明,一部分锰淀积在GaAs的表面形成一层厚度约为30nm的外延层,另一部分锰离子成功注入到GaAs基底里,注入深度约为160nm。补底温度为523K时获得了Ga5.2Mn相,补底温度为673K时获得了Ga5.2Mn、Ga5Mn8和Mn3Ga相。在1113K条件下对673K生长的样品进行退火,退火后样品中原有的Mn3Ga消失,Ga5Mn8峰减弱趋于消失,Ga5.2Mn仍然存在而且结晶更好,并出现Mn2As新相。     

MBE法InAs异质外延

用 MBE 法实现了无孪晶 InAs 外廷生长、基底为 GaAs(111)B,取向偏差0.5°。外延层厚2μm,其 X 射线回摆曲线的半高宽为200弧秒。在 InAs 生长过程中,其反射式高能电子衍射(RHEED)图形为条纹,无额外斑点出现。而生长     

Au/Ni/Al/Ti/AlxGa1-xN/GaN和Au/Pt/Al/Ti/AlxGa1-xN/GaN欧姆接触研究

研究并对比了Ti/Al/Ni/Au和Ti/Al/Pt/Au多层金属膜与未掺杂的Al0 .2 2 Ga0 .78N/GaN(i AlGaN/GaN)异质结构之间的欧姆接触性质。在退火温度低于 70 0℃时 ,两种接触样品上都不能得到欧姆接触。随着退火温度的升高 ,85 0℃快速退火后 ,在Ti/Al/Ni/Au接触上获得了 1.2 6×10 - 6 Ω·cm2 的比接触电阻率 ,在Ti/Al/Pt/Au接触上获得了 1.97× 10 - 5Ω·cm2 的比接触电阻率。研究结果表明 ,金属与半导体接触界面和Al0 .2 2 Ga0 .78N异质结构界面载流子沟道之间适当的势垒的存在对高质量欧姆接触的形成起重要作用 ,势垒的宽度取决于退火温度以及退火的具体进程。对Ti/Al/Ni/Au和Ti/Al/Pt/Au欧姆接触比接触电阻率的差异进行了解释。     

用于1.44 μm半导体激光器的GaInAs/InGaAsP量子阱结构的设计

采用有效质量模型下的 4× 4Luttinger Kohn哈密顿量矩阵对GaxIn1 -xAs/In0 .80 Ga0 .2 0 As0 .4 4P0 .56 /InP量子阱结构进行了能带计算 ,求得了该量子阱结构跃迁能量随组份及阱宽的变化关系 ,从而得到了激射波长 1.44 μm时的Ga组份x与阱宽Lw(在 5～ 10nm内取值 )的相互关系 :x=0 .3 2 0 13 0 .0 60 93Lw-0 .0 0 5 3 4Lw2 0 .0 0 0 17483Lw3,当阱宽为 5～ 10nm ,因而Ga组份为 0 .5 1～ 0 .5 7时 ,阱材料中产生的张应变量为 :0 .2 9%～ 0 .70 %。最后 ,我们计算了该量子阱结构的能量色散关系和光增益谱 ,从而对x与Lw 组合值进行优化。     

四阱耦合InGaAs/InAlAs/InP量子级联激光器材料的结构特性研究

报道了用气态源分子束外延 (GSMBE)技术生长的InAlAs/InGaAs四阱耦合量子级联激光器 (QCL)材料的结构特性。X射线双晶回摆曲线谱测量结果表明所生长的QCL有源区的界面 (含 770层外延层 )、厚度达到单厚子层控制 ,组份波动≤ 1% ,晶格失配≤ 1× 10 - 3。采用特殊的优化工艺 ,Φ5 0mm外延片的表面缺路陷密度降至 1× 10cm- 2 ,达到了器件质量的要求。     

In_x Ga_(1-x)As/InP异质材料的气相外延研究

本文采用氯化物法In-Ga-AsCl_3-H_2体系进行InGaAs/InP的异质气相外延研究。对采用In/Ga混合源和铟、镓的独立金属源的外延体系进行了比较。采用尽可能大的In(InAs)面积并降低晶格失配率的同时,注意提高原材料纯度,是制备优质多元外延材料的必要条件。     

双缓冲层法在硅上外延生长GaN研究

利用金属有机物化学金相沉积MOCVD在Si(111)衬底上，以高温AlN和低温GaN为缓冲层生长的GaN薄膜，得到GaN(0002)和(10-12)的双晶X射线衍射(DCXRD)半高宽(FWHM)分别为721和840s。采用高分辨率DCXRD，扫描电子显微镜(SEM)分析。结果表明，以1040℃生长的AlN缓冲层能防止Ga与Si反应形成无定形的Si-Ga结构，是后续生长的“模板”。低温的GaN缓冲层可有效减低外延层的缺陷。DCXRD测得的FWHM为0．21，GaN峰强达7K。     

The classification of graphical elements.

In three experiments, participants classified stimuli depicting pie charts and stacked bar graphs on two criteria: a proportion shown in the graph, and the graph's overall size (scaling). Sorting times and errors were measured. For stacked bars, performance was impaired when participants sorted on the proportion and scaling varied. No such impairment occurred for pie charts. Experiment 1 showed that varying scaling produced Garner interference in classification of proportions with stacked bars, but not pies. Experiment 2 showed that this result held when the position of the pie slice was varied; Experiment 3 results showed facilitation for particular combinations of proportion and scaling levels. In general, the results showed that proportion and scaling had an asymmetric integral relation for stacked bar graphs, but were separable dimensions for pie charts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Purification and proteic characterization of a Cuban strain of the hepatitis A virus

The testicular toxicities of gallium arsenide (GaAs), indium arsenide (InAs) and arsenic trioxide (As2O3) were examined by repetitive intratracheal instillation using hamsters. GaAs (7.7 mg/kg) and As2O3 (1.3 mg/kg) were instilled twice a week a total of 16 times and InAs (7.7 mg/kg) was instilled a total of 14 times. GaAs caused testicular spermatid retention and epididymal sperm reduction, though the degrees were less severe than those in rats shown in our previous experiment. InAs and As2O3 did not show any testicular toxicities. Serum arsenic concentration in GaAs-treated hamsters was less than half of that in As2O3-treated hamsters in which no testicular toxicities were found. Serum molar concentration of gallium was 32-times higher than that of arsenic in GaAs-treated hamsters. Therefore gallium may play a main role in the testicular toxicity of GaAs in hamsters.     

Immunofluorescent Labeling of Human HepG2 Cells with CdTe Quantum Dot Probe Conjugated with Anti-pan CK MAb

A relatively sensitive, specifiC., and photostable method for the detection of cytokeratin of cancer cells via conjugation with cadmium telluride quantum dots(CdTe QDs) was described. Water soluble CdTe QDs were conjugated to anti-pan-cytokeratin(CK) monoclonal antibody(MAb) through coupling reagent [1-ethy1-3-(3-dimethylamino propyl)carbodiimide, EDC] and the conjugates were purified by dialysis. The expression of pan CK protein in HepG2 cells was observed by immunocytochemistry and direct immunofluorescence via QDs-Ab conjugates respectively. Fluorescence intensity and photostability of QDs were compared with those of FITC(fiuorescein isothiocyanate). The results show that the QDs-Ab conjugates recognized specifically pan CK protein in HepG2 cells. Compared with FITC., CdTe QDs had higher brightness and photostability without obvious photobleaching under continuous exciting light illumination for 30 min and after the placement at room temperature for 3 d. The results indicate that conjugates of CdTe quantum dot with anti-pan CK MAb can be used for labeling cancer cells derived from epithelial tissues, which provides the basis for the detection of circulating tumor cells(CTCs).     

四脚状CdSe敏化TiO2纳米管阵列薄膜光电性能研究

采用阳极氧化法在钛基底上生长了一维高度有序TiO2纳米管阵列,并与CdSe四脚状晶体及CdSe量子点组装成一种新型的量子点敏化太阳能电池( QDSSCs).该阵列结构为光生电子的传递提供了快速通道,CdSe四脚状三维空间结构增加了其吸附在TiO2纳米管阵列的稳定性.采用XRD,SEM和HR-TEM对阵列及CdSe四脚状和量子点进行了表征.考察了CdSe四脚状和量子点敏化纳米管阵列三电极电池结构的光电性能.XRD谱图表明TiO2的锐钛矿晶型特征峰没有发生变化,同时出现了一系列的CdSe六方晶型和立方晶型特征峰.SEM图表明所制备的TiO2具有高度有序的纳米管阵列结构,且孔径大小均一、约为120 nm,长度近13.8 μm.TEM和HRTEM图表明CdSe量子点具有四脚结构,CdSe核的直径约为4.1nm,臂宽约为3.1nm,臂长约为16.0nm.结果表明:通过四脚状CdSe修饰TiO2纳米管阵列基电极在可见光谱区域的吸收得到了明显增强;此外,在模拟太阳光(AM 1.5 100 mW·cm-2)的照射下,四脚状CdSe敏化比CdSe量子点敏化TiO2纳米管阵列三电极结构电池的光电转换效率高,它们分别为0.13％和0.30％.     

Hydraulics of Stacked Drop Manholes

This paper presents the results of an experimental investigation on flows inside stacked drop manholes (SDM). An SDM consists of two identical rectangular or square manhole chambers stacked together at an elevation difference. SDMs for different conditions were assessed on their ability to dissipate the energy of the approaching flow and their suitability to perform adequately under different flow conditions. Flow regimes were classified based on the inflow conditions and geometry of the structure in the first chamber and downstream outflows in the second chamber. An analysis based on the integral momentum equation was developed to estimate pool depths and energy losses under critical flow conditions. A fully surcharged stage with inflow and outflow pipes running full was also tested and velocity profiles were measured at a horizontal center plane to the opening connecting both shafts. Additionally, air flow rates were measured to assess the air demand into a large-height SDM.     

Determination of Shear-Wave Velocities and Shear Moduli of Completely Decomposed Tuff

Based on theoretical derivations and considerations, five series of laboratory tests were planned to investigate and differentiate the degrees of inherent and stress-induced anisotropy, to study the effect of void ratio changes on shear-wave velocities and shear moduli, and to determine the relationship between shear-wave velocity and stress state on a completely decomposed tuff (CDT). Shear-wave velocities in three orthogonal horizontal and vertical planes [vs(hh), vs(hv), and vs(vh)] were measured in both vertically and horizontally cut block and Mazier specimens. Under isotropic stress conditions (K = 1.0), the degrees of inherent anisotropy [vs(hh)2/vs(hv)2 = Ghh/Ghv] were 1.48 and 1.36 for the block and Mazier specimens, respectively. At the anisotropic stress state (K = 0.4), the degrees of anisotropy of the block and Mazier specimens were 1.26 and 1.15, respectively, 15% reduction from the measured inherent anisotropy due to stress-induced effects. The measured higher shear-wave velocity in the horizontal plane of the CDT was confirmed by testing both vertically and horizontally cut specimens and the measured results reflect a stronger layering structure in the horizontal bedding plane of the natural material, in which K0 less than 1.0 is commonly assumed in designs. Under both isotropic and anisotropic stress states, the shear-wave velocities [vs(hh), vs(hv), and vs(vh)] of the block specimens are on average about 27% higher than those of the Mazier specimens.     

Nanocomposites of CsPbBr3 perovskite quantum dots embedded in Gd2O3:Eu3+ hollow spheres for LEDs application

Gd₂O₃:Eu³⁺@CsPbBr₃ quantum dots (QDs) mesoporous hollow nanocomposites with good luminescent properties and high stability were built. Among which, the hollow Gd₂O₃:Eu³⁺ spheres and CsPbBr₃ QDs were prepared by urea homogeneous precipitation and hot-injection method, respectively. Finally, the Gd₂O₃:Eu³⁺@CsPbBr₃ QDs shell–core compounds were constructed through mechanical stirring. The structure, morphology, stability and luminescent properties were studied by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry/thermogravity (DSC/TG), X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence excitation/photoluminescence (PLE/PL) and life decay tools. Compared to the original CsPbBr₃ QDs, Gd₂O₃:Eu³⁺@CsPbBr₃ QDs display better photostability, thermal stability and current stability. The resulting Gd₂O₃:Eu³⁺@CsPbBr₃ QDs composite exhibits good yellow emission. The Gd₂O₃:Eu³⁺@CsPbBr₃ QDs mixed silicone resin was directly coated on the blue LED chip, then the w-LED device with the color coordinate of (0.31, 0.32) was successfully assembled. The Gd₂O₃:Eu³⁺@CsPbBr₃ QDs compounds with excellent luminescent properties and stability are expected to be widely used in lighting and display areas.     

Friction Factor of Meandering Flows

An expression for the friction factor of rough turbulent meandering flows is suggested: flow cross section is rectangular, the plan shape of the meandering channel is sine-generated. This expression gives the value of the friction factor as a function of position (which is determined by, among other factors, the local channel curvature) and channel sinuosity. The validity of the present expression is tested against results of laboratory measurements. The measurements were carried out in two meandering channels, one typifying “small” sinuosity, the other “large” sinuosity. It is found that the vertically averaged flows in these two channels exhibit two distinctly different (“in-” and “out-going”) flow patterns, depending on whether the channel sinuosity is “large” or “small.” These two radically different flow pictures cannot be supplied by the vertically averaged equations of motion if they are solved for a constant friction factor. The present consideration of the friction factor as a function of position and channel sinuosity is found to yield the computed vertically averaged flows that are in agreement with the flow pictures measured for both large and small values of sinuosity.     

Vertical Pt-C replication for TEM, a revolution in imaging non-periodic macromolecules, biological gels and low-density polymer networks

Vertical replication for TEM is ideal for studying non-periodic specimens from 0.7 to 3 nm, a resolution mid-range difficult to attain by any other technique. This paper discusses the importance of vertical replication, its methods and hardware for high-resolution TEM. Evidence from diverse published research will demonstrate vertical replication's versatility in imaging the molecular level normally unattainable in freeze-dried polymers, polyethylene tribological wear on surfaces, low-density polymer networks or biological gels. Vertical platinum-carbon (Pt-C) replication minimizes the horizontal movement of Pt-C on a surface. Surface objects are symmetrically enlarged by a vertically deposited Pt-C film. To estimate real size in replicas, 16-25 particles or filaments need to be measured in calibrated transmission electron microscopy (TEM) images and reduced by a value less than the Pt-C film thickness measured with a quartz monitor. Continuous, vertically deposited Pt-C films are formed on mica at a deposition thickness of around 1.0 nm and on silver at a thickness of 0.4-0.5 nm. The distance between helical turns in poly(1-tetradecene sulfone) of 0.7 nm is the highest resolution achieved with vertical replication. Two polysulfones freeze-dried and vertically replicated on mica contained structures are predicted by indirect physical chemical methods to be present in solution. Polymer chains are fully Pt-C coated, with no uncoated gaps along chains. Some side-chains on the extended non-helical poly(1-tetradecene sulfone) are also detected. To estimate the real chain width, polymer chains measured in images are reduced by the Pt-C film thickness minus 0.5 nm. The polymer chain widths estimated from molecular models are in the same range of widths as those measured using the image size correction method. Also, it is possible to distinguish random coil proteins (chain width of around 0.5 nm) from an alpha-helix (chain diameter of about 1 nm) in vertically replicated samples on silver substrates. In the future, subnanometer resolutions below 0.7 nm should be possible. The resolution of vertical replication depends on the thickness of a continuous, amorphous Pt-C film. That thin, continuous 0.4-0.5 nm Pt-C films on silver substrates can be made suggests that a point-to-point resolution limit of around 0.28 nm in TEM may ultimately be approachable with replication.     

Does Filtration Efficiency Affect Measurements of Particle Chemical Composition?

A direct method to measure filtration efficiency was developed and used for the determination of the efficiency of a Nuclepore filter. This needs two equivalent filtration systems operated in sequence. The amount of particulate matter collected on each system is measured and introduced in a simple formula. The particulate masses deposited on the filters in each system were measured as total mass, by balance gravimetry, and as individual elemental masses, by PIXE (particle induced X-ray emission). With this very general method it was possible to determine the efficiencies of a 0.4 μm Nuclepore filter operated with a stacked filter unit for particles less than 2.5 μm in total mass and elemental masses. The experiment showed that the efficiency of this filter is very poor for some specific elements, like sulfur, that are concentrated in very small particles.