Hydrogen plasma passivation of bulk GaAs and Al0.3Ga0.7As/GaAs multiple-quantum-well structures on Si substrates

Hydrogen (H) plasma passivation effects on GaAs grown on Si substrates (GaAs on Si) are investigated in detail. H plasma exposure effectively passivates both the shallow and deep defects in GaAs on Si, which improves both the electrical and optical properties. It was found that the minority carrier lifetime is increased and the deep level concentration is decreased by the H plasma exposure. In addition, after H plasma exposure, room temperature photoluminescence (PL) for Al_0.3Ga_0.7As/GaAs multiple-quantum-well (MQW) on Si is enhanced with a decrease in the spectral width.     

形变铜中位错组态的电镜分析

本文用ＴＥＭ衍射成像技术观察在室温下形变铜中位错胞结构的产生与发展，测定了胞壁厚及位错环尺寸等应变的变化规律，并探讨了胞尺寸与位错密度，流变应力之间定量关系的存在。     

LED用非极性GaN外延膜的制备技术进展

GaN是实现白光LED的关键材料。GaN外延膜通常沿极性c轴生长,基于极性GaN的LED有源层量子阱中由于强内建电场的存在而导致器件发光效率降低,而沿非极性面生长的GaN外延膜可以改善或消除极化效应导致的辐射复合效率降低和发光波长蓝移等问题。文章总结了非极性GaN外延膜的制备技术及研究进展,包括平面外延技术和横向外延过生长技术,指出开发非极性GaN自支撑衬底、发展非极性GaN的横向外延生长技术是制备低位错密度非极性GaN的研究方向。     

The isolation and nucleation of misfit dislocations in strained epitaxial layers grown on patterned,ion-damaged GaAs

As shown previously, the misfit dislocation density of strained epitaxial III–V layers can be significantly reduced by isolating sections (via patterned etching) of a GaAs substrate before epitaxial growth. A disadvantage of this technique is that the wafer surface is no longer planar, which can complicate subsequent device fabrication. As an alternative, we have investigated growth of 350 nm of In_0.5Ga{0.95}As by molecular beam epitaxy at two temperatures on substrates which were patterned and selectively damaged by Xe ion implantation (300 keV, 10¹⁵ cm²). Selectively etched substrates were prepared as reference samples as well. The propagation of the misfit dislocations was stopped by the ion-implanted regions of the low growth temperature (400° C) material, but the damaged portions also acted as copious nucleation sources. The resulting dislocation structure was highly anisotropic, with dislocation lines occurring in virtually only one direction. At the higher growth temperature (500° C) the defect density fell, but the ion damaged sections no longer blocked dislocation glide. Images from cathodoluminescence and transmission electron microscopy show thatthe low growth temperature material has a dislocation density of 70,000 cm^-1 in the 110 direction and less than 10,000 cm^-1 in the 110 direction. Ion channeling and x-ray diffraction show that strain is relieved in only one direction. The strain relief is consistent with the relief derived from TEM dislocation counts and Burgers vector determination. However, even this high dislocation count is not sufficient to reach the expected equilibrium strain. Reasons for the anisotropy are discussed.     

微尺度涡旋位错:宝石晶体又一重要的生长机制

采用原子力显微镜、干涉显微镜对水热法合成蓝宝石和天然绿柱石等宝石的表面微形貌进行了研究. 通过对宝石晶体中微尺度涡旋位错的表征和示踪, 初步证实涡旋位错是某些宝石矿物晶体又一重要的生长机制. 这暗示, 微尺度成矿流体的涡旋运移与晶相涡旋成核可能是地球成矿动力学体系中某些物质运动和存在的又一种重要的形式. 对晶体生长机理的研究现状和发展趋势予以了讨论.     

错位纺纱对成纱性能的影响

采用错位纺纱技术在DSSP-01型数字式小样细纱机上纺制不同细度不同捻向的纯棉纱,通过纱线性能测试探讨错位方向对不同粗细和不同捻向纱线成纱性能的影响.实验结果表明,错位纺纱对成纱断裂强度和成纱条干有不同程度的改善,但是错位纱的断裂伸长率降低;由于吸棉笛管和导纱钩的不匹配,错位环锭纱毛羽显著增加.     

冷拔碳素钢丝的纤维组织及其亚结构

用光学显微镜、透射和扫描电镜观察、分析冷拔碳素钢丝的纤维组织及其亚结构的形貌和特点,指出它对钢丝力学性能及断裂行为的影响,对金属制品生产者和用户加深对材料的认识有重要的理论和实际意义     

Dispirations,disclinations, dislocations,and chain twist in polyethylene crystals

It is proposed that the twist in polyethylene chains that can result from crystallization and subsequent deformation aggregates at boundaries and becomes a template for further reorganization that results in the long period observed in polyethylene fibres. The observed lower density at the boundaries requires the transport of free volume to the twist boundaries. Dispirations, disclinations and dislocations are crystallographic defects that are involved in the necessary transport mechanism. Twist and bend, derived from the Eulerian angles which are computed from the sets of chain internal coordinates, relate the orientation of different segments of a chain. Twist and bend are useful for the characterization of both crystallographic defects and arbitrary conformations of polymer chains. Defects, along with folds, chain ends, and ordinary edge and screw dislocations provide a basis for interpretation of structure-property relationships in solid polyethylene.     

Twinning and mechanical behavior of titanium aluminides and other intermetallics

Based on the recent studies of deformation twinning in ordered intermetallics, the general background on slip-twinning-microcracking relationships is established. Specific roles of deformation twinning in the generalized plasticity of polycrystals and the crack-tip microplasticity are discussed in terms of the local strain compatibility by invoking both ‘tension’ and ‘compression’ twins. Special examples are given for γ-TiAl, other L1₀ alloys, and Ti₃Al of the D0₁₉ structure. Effects of composition, microstructure and temperature on defect properties that are relevant to the propensity of deformation twinning are discussed.     

9SiCr钢中的筐篮编结状马氏体及其性能

将9SiCr钢的粒状原始组织改变为片状,再经830℃淬火后,其马氏体形态为筐篮编结状。而传统工艺所获得的马氏体形态为针状.这种筐篮编结状马氏体是9SiCr钢中一种崭新的组织形态,其精细结构为平行成束的板条。亚结构为高密度缠结位错.它有良好的综合机械性能,强韧性高,耐磨性高。