Effect of growth-interrupted method on quality of AlGaAs/GaAs multiple quantum wells prepared by MBE

AlGaAs/GaAs multi-quantum well （MQW） was prepared by molecular beam epitaxy（MBE） with growth-interrupted heterointerface （GIH） method and continuous growth （CG） method, respectively. The microstructures Of the MQWs were characterized by double-crystal X-ray rocking curve （DCRC） and atomic force microscopy （AFM）, and the photoluminescence （PL） properties of the MQWs were also studied. The MQWs grown with GIH method show that higher order satellite peaks of Pendelloesung fiinges are observed in DCRC, the roughness of surface is much reduced in AFM, and the full width at half maximum （FWHM） of exciton line is much narrower in PL. The results indicate that the GIH method reduces the monolayer growth step density at the heterointerface due to the migration of surface atomsfor a few minutes grower interruption, and substantially improves the quality of AlGaAs/GaAs MQWs.     

Observations on the uniformity of immersion tin coatings on copper

The development of chemical tin coatings by a replacement reaction Cu+Sn²⁺Cu²⁺+Sn from hydrochloric acid based and methanesulphonic acid based baths on the inner surface of a copper tube was studied by transmission electron microscopy and scanning electron microscopy in order to explore the factors influencing the uniformity of tin coatings. Despite the fact that tin coatings develop in different ways in studied baths, uniform coatings are equally plated from both these baths when the substrate surface is clean and smooth. However, differences in the surface-sensitivity, i.e. the dependence of coating uniformity on the substrate surface condition, of plating baths materialise when plated on irregular or improperly cleaned substrate. A hydrochloric acid based bath may yield non-uniform coatings on irregular or improperly cleaned substrate, since large-sized grains develop immediately after coating initiation. These large grains are suggested to orientate to follow the contours of impurity particles or surface irregularities introducing misalignment in grain columns and, thus, non-uniformity into coatings. In contrast, a methanesulphonic acid based bath is still able to produce uniform tin coatings on contaminated or rough surfaces, as the coating is proposed to accommodate to substrate surface irregularities by the build-up of a nanocrystalline zone at the early stages of tin coating deposition. Sulfur-containing elements in this methanesulphonic acid based plating bath play the central role in the nanocrystalline layer formation.     

Influence of GaCl carrier gas flow rate on properties of GaN films grown by hydride vapor-phase epitaxy

The influence of GaCl carrier gas flow rate on GaN films grown by hydride vapor-phase epitaxy (HVPE) was investigated. The symmetric (0 0 0 2) and asymmetric (10-12) ω scans were detected to estimate the quality of GaN films. Optical properties were studied by room temperature photoluminescence spectra. Raman spectroscopy was employed to analyze the residual stress in the samples. The surface morphology of the GaN films was investigated by atomic force microscopy (AFM). On the basis of process optimization the optimal GaCl carrier gas flow rate for growth of high quality GaN films in our system was obtained as 1.3 L/min.     

台湾LED/OLED光电材料与组件技术的发展

台湾发光二极管（Light Emitting Diode,LED）的产量已达到世界第一,产值则居世界第二。将回顾台湾发光二极管产业的发展历史,并探讨产业界及研发单位在发光二极管效率提升与质量改善方面的一些重要技术发展历程。有机电激发光（OLED）组件的发展过程,除了显示器的应用发展优势之外,固态照明也是台湾近期的研发重点之一,文中将探讨磷光有机材料、组件结构技术的开发及OLED的发展趋势。     

Study of oxygen and carbon species on Si substrate during in-situ cleaning prior to high-quality epitaxial deposition

We investigated the effect of in-situ cleaning with ECR (Electron Cyclotron Resonance) hydrogen plasma. This cleaning was effective in removing oxygen and carbon on the wafer surface because of its high density and low substrate damage and, thus, high quality epitaxial films were deposited. The contents of the oxygen or carbon species were correlated with the structural quality of the interface and film. The possible reaction mechanisms for the cleaning of oxygen and carbon species were scrutimized. The removal of oxygen rather than of carbon, was crucial in obtaining high quality epitaxial films.     

Influence of twist and filament location in a yarn on effectiveness of atmospheric pressure plasma jet treatment of filament yarns

A twist free polyethylene terephthalate (PET) filament tow and ultrahigh modulus polyethylene (UHMPE) filament tows with 0, 1, 2, and 3 twist/cm are used as model systems to investigate the penetration of atmospheric pressure plasma jet modification effects through a single yarn. The change in surface wettability is determined using static contact angle measurements. Morphological and chemical changes on the fiber surface are characterized by scanning electron microscopy and X-ray photoelectron microscopy. The adhesion improvement is analyzed by micro-bond pullout test. For the PET filament tow, the fibers from the middle layer tend to have poorer treatment effect than those from the top and the bottom layers in terms of surface roughness, wettability and surface chemical composition change. For the UHMPE yarns, as the twist level increases, the plasma treatment is less effective in improving the fiber surface chemical composition, wettability and interfacial shear strength to epoxy due to the tightened yarn structure.     

Growth of N-polar GaN on vicinal sapphire substrate by metal organic chemical vapor deposition

The growth and properties of N-polar Ga N layers by metal organic chemical vapor deposition(MOCVD) were reported. It is found that N-polar Ga N grown on normal sapphire substrate shows hexagonal hillock surface morphology. With the misorientation angles increasing from 0.5° to 2.0° toward the a-plane of the sapphire substrate, the number of the hillock becomes less and less and finally the surface becomes flat one on the sapphire substrate with the misorientation angle of 2°. It is also found that the crystalline quality and the strain in the Ga N are greatly influenced by the misorientation angle.     

误差对平面滑块机构运动特性的影响研究

应用误差理论，具体研究了两种典型机构误差对机构运动特性影响，结果表明，机构误差对高速机构的运动特性的影响较大，尤其是对调整机构的速度及加速度的影响更大，其影响程度呈数量级增长，这为平面滑块机构的设计提供了依据。     

Effect of growth interruption and strain buffer layer on PL performance of AlGaAs／GaAs／InGaAs quantum well for 1065 nm wavelength lasers

Strained InGaAs/GaAs quantum well (QW) was grown by low-pressure metallorganic chemical vapor deposition (MOCVD). Growth interruption and strain buffer layer were introduced to improve the photoluminescence (PL) performance of the InGaAs/GaAs quantum well. Good PL results were obtained under condition of growth an interruption of 10 s combined with a moderate strain buffer layer. Wavelength lasers of 1064 nm using the QW were grown and processed into devices. Broad area lasers (100 μm × 500 μm) show very low threshold current densities (43 A/cm2) and high slop efficiency (0.34 W/A, per facet).     

镍的金属有机化学气相沉积及相关因素的研究

研究了以碳基镍为沉积源，利用MOCVD技术沉积镍薄膜；讨论了沉积温度及压力对沉积速率的影响，以及利用SEM、XRD、DSC等分析手段来探讨沉积温度及不同沉积基体对薄膜微观形态的影响。结果表明，沉积温度约为150℃可以得到较快的沉积速率，而且薄膜连续具有金属光泽；以铜为沉积基体所得到的薄膜其微观形态中有明显的晶粒，以玻璃为基体得到的薄膜却含有部分非晶态的组织；沉积速率随着反应室工作压力的增加而下降。     

再论轻重铂族元素配合物化学性质之差异

深入讨论了重铂族离子有效核电荷Ｚ＾＊及ｄ轨道能级分裂△０值高于轻铂族的原因。用文献中大量可比资料，再次论证重铂族配合物的热力学稳定性和动力学惰性高于轻铂族配合物。     

Controlling the growth of CVD carbon from methane on transition metal substrates

A hot-wall chemical vapor deposition (CVD) method was employed to grow crystalline graphitic carbon on transition metal substrates. Temperature dependence of the CVD carbon growth and the influence of methane concentration (carbon source) on the growth rate of carbon were systematically investigated. The effect of the substrate on the growth rate and carbon crystallinity was also investigated. These factors, temperature, methane concentration, and type of substrate, influenced the growth of CVD carbon. The carbon growth pattern appears to start with the most crystalline graphitic carbon being produced on the surface of the Fe and Ni and becomes more amorphous as the coating thickness increases.     

铑(Ⅲ)氯水配合物在水溶液中的热力学和动力学平衡行为研究

作者详细研究了各铑(Ⅲ)氯水配合物在水溶液中随时间、温度变化而变化的规律,获得的结果表明,CT浓度是影响铑(Ⅲ)在各种态中分布的主要因数,但是,对于阴离子种态,其放置的时间和温度也是不可忽略的。对于下面这个短的平衡反应链：fac-[RhCl3(H2O)3]→←K34^c cis-[RhCl4(H2O)2]^-→←K45^c [RhCl5(H2O)]^2-→←K56^c [RhCl6]^3-作者系统的研究了在不同温度下其各种态的分布,结果发现,fac-[RhCl3(H2O)3]的含量随温度的升高而增加,而cis-[RhCl4(H2O)2]^-、RhCl5(H2O)]^2-和[RhCl6]^3-却随温度的升高而降低。氯代和水合作为铑(Ⅲ)氯水配合物在溶液中的竞争反应,在放置开始,氯代占优势,但随时间的延长,水合逐渐趋于优势。     

Comparative study of patinas formed on statuary alloys by means of electrochemical and surface analysis techniques

A comparative evaluation of natural patinas and those formed during acid rain laboratory tests was applied to predict patina stability in corrosive urban environments. SEM-EDX analyses of various statuary alloys after the laboratory tests distinguished areas of correlative intensity of attack and S percentage, depending on the alloy. Moreover, EDX and X-ray diffraction (XRD) determined the chemical composition of different coloured patina carefully scraped from a bronze monument, submitted to 75 years outdoors exposure.To analyse the electrochemical potential evolution with time the in situ Pourbaix technique was applied on the laboratory-exposed samples and over representative areas of the monument, at 2 years interval.     

Chemical vapor deposition of rhenium on a gourd shaped graphite substrate

Chemical vapor deposition (CVD) of rhenium coatings on a gourd shaped graphite substrate is studied. Effects of deposition temperature, chlorine flow rate, total pressure and chlorination temperature on deposition rate, yield, morphology and texture of rhenium coating are investigated, respectively. Uniform rhenium coatings have been obtained by using proper combination of deposition conditions at an acceptable deposition rate and yield. The rhenium coatings consist of two sub-layers, i.e., an inner nucleation layer of fine equiaxed grains and an outer layer comprising oriented columnar grains. Although different surface morphologies have been observed, the grains of rhenium coatings are all <002> oriented. The tendency of the preferred orientation <002> is more significant with decreasing surface roughness of the coating.     

改良剂对As、Cd、Pb污染土壤上芦竹生长及重金属吸收的影响(英文)

通过室内盆栽试验研究在As、Cd和Pb复合污染土壤中施用醋酸、柠檬酸、EDTA、海泡石和磷石膏5种改良剂对芦竹生长及重金属吸收的影响。结果表明,施加5.0mmol/kg柠檬酸或2.5mmol/kgEDTA时,芦竹地上部生物量较没添加的对照的分别增加了24.8%和15.0%,芦竹叶片中过氧化氢酶及过氧化歧化酶活性较对照的无显著变化。与对照相比,添加2.5mmol/kg醋酸、2.5mmol/kg柠檬酸、5.0mmol/kgEDTA及4.0g/kg海泡石时,地上部中As、Cd、Pb的浓度显著增加(P0.05)。改良剂能明显提高芦竹地上部重金属累积量,地上部中As、Cd的累积量在上述条件下均显著增加(P0.05),Pb累积量在添加4.0g/kg海泡石和8.0g/kg磷石膏时显著高于对照(P0.05)。醋酸、柠檬酸和海泡石可作为合适改良剂促进重金属污染土壤上芦竹对土壤中重金属的累积。     

The atmospheric corrosion of copper at two sites in Portugal: a comparative study

This paper presents a comparative study on the atmospheric corrosion of copper, at two sites, in Portugal, with exposures started in two different seasons (summer and winter). Particular attention is devoted to the initial stages of the corrosion process.The levels of pollutants, namely of SO₂ and chlorides, in both atmospheres, have been measured, over the periods from August 1999 to July 2000 and from November 2000 until July 2001. Climatic data for both sites and both periods has been collected and analysed.Kinetics of the corrosion process (weight losses) have shown to be described by: Δm=kt^0.6 and Δm=kt^0.4, with k equal to 3.4 (g m⁻² month^−0.6) and 17 (g m⁻² month^−0.4), for the one year exposures, started in summer, at the urban and maritime atmospheres, respectively. Exposures started in winter, at the urban atmosphere, have lead to kinetics described by Δm=kt^0.7 with k=5.0 (g m⁻² month^−0.7).The chemical composition and the morphology of the copper patinas, corresponding to exposures of 2 and 12 months, at the two sites, are compared as well as the morphology of the corroded surfaces.     

Comparative study of ZnO nanostructures grown on silicon (1 0 0) and oxidized porous silicon substrates with and without Au catalyst by chemical vapor transport and condensation

ZnO tetrapods and rods were grown on silicon and thermally oxidized porous silicon substrates with and without Au catalyst layer by carbothermal reduction of ZnO powder through chemical vapor transport and condensation method (CVTC). Porous silicon was fabricated by electrochemical etching of silicon in HF solution. The effect of substrates on morphology, structure and photoluminescence spectra of ZnO nanostructures has been studied. The texture coefficient (TC) of each sample was calculated from XRD data that demonstrated random orientation of ZnO nanostructures on the oxidized porous silicon substrate. Moreover, TC indicates the effect of Au catalyst layer on formation of more highly oriented ZnO nanorods. The morphology of the samples was investigated by SEM which confirms formation of ZnO nanostructures on oxidized porous silicon substrates with and without catalyst. A blue-green emission has been observed in ZnO nanostructures grown on Si and the oxidized PS substrates without Au catalyst layer by PL measurements.     

反应动力学法评价MOCVD过程中金属有机盐的稳定性

在MOCVD技术中,金属前驱盐持续稳定蒸发是获得高质量YBa₂Cu₃O_7-δ(YBCO)超导薄膜的关键。随着新型高挥发金属有机盐的不断涌现,亟需一种评价金属前驱盐在蒸发过程中稳定性的实用方法。本文基于MOCVD法制备YBCO超导体过程中常用的、具有不同蒸发特性的三种金属前驱盐(Y(DPM)₃, Cu(DPM)₂, Ba(DPM)₂),采用非等温热重分析法对比研究三种金属前驱盐在蒸发过程中的热稳定性和分解动力学特性,并依据典型动力学方法(Ozawa, Kissinger和Friedman法)计算获得各金属前驱盐在蒸发过程中的表观活化能(E_a)及其变化规律,进而分析评价其在蒸发过程中的热稳定性。研究结果表明：Ba(DPM)₂金属前驱盐在蒸发过程中会伴随发生热分解反应,且分解过程对温度变化敏感,而Y(DPM)₃和Cu(DPM)₂可以稳定蒸发。结合TGA-DSC分析证实,采用固相反应动力学方法来评价MOCVD过程中金属前驱盐的热稳定性是可靠的。