基于三轴X射线衍射方法的n-GaN位错密度的测试条件分析

三轴X射线衍射技术广泛应用于半导体材料参数的精确测试,然而应用于纤锌矿n-GaN位错密度的测试却可能隐藏极大的误差.本文采用三轴X射线衍射技术测试了两个氢化物气相外延方法生长的n-GaN样品,发现两样品对应衍射面的半高全宽都基本一致,按照镶嵌结构模型,采用Srikant方法或Williamson-Hall方法,两样品的位错密度也应基本一致.但van der Pauw变温霍尔效应测试表明,其中的非故意掺杂样品是莫特相变材料,而掺Si样品则是非莫特相变材料,位错密度有数量级的差别.实验表明,位错沿晶界生长导致的晶粒尺寸效应,表现为三轴X射线衍射技术检测不到晶界晶格畸变区域的位错,给测试带来极大误差,这对正确使用Srikant方法和Williamson-Hall方法提出了测试要求.分析表明,当扭转角与倾转角之比β_(twist)/β_(tiit)≥2.0时,Srikant方法是准确的,否则需进一步由Williamson-Hall方法确定晶粒大小(面内共格长度L//),当L//≥1.5μm时,Srikant方法是准确的.     

高功率直流电弧等离子体喷射法制备的金刚石厚膜中黑色缺陷的研究

借助激光标记的方法,对采用高功率直流电弧等离子体喷射法制备的金刚石膜中的黑色缺陷进行了定点表征.结合使用光学显微镜、激光扫描共焦显微镜、扫描电子显微镜、电子背散射衍射技术等多种表征方法,对同一样品的特定微观标记区域进行了多角度的分析.实验结果表明:金刚石膜内部的黑色缺陷是一种存在于晶界处的孔洞与质量较低的金刚石相的复合体,它的形成应与金刚石膜中某些晶界处的生长环境有关.     

节理玄武岩体变形模量的尺寸效应和各向异性

目前系统研究柱状节理玄武岩工程力学特性的成果仅见于美国汉佛德玄武岩核废料埋藏工程和中国西南白鹤滩水电工程。列举了国内外相似工程柱状节理玄武岩的原位试验成果,分析了我国不规则柱状节理玄武岩体的柱体偏转特性和多级结构面发育特征,采用可变形离散元法建立了柱状节理玄武岩体的三维离散元数值模型,通过数值模拟不同尺寸的承压板试验,探讨了尺寸效应和各向异性对试验成果的影响。数值分析表明：承压板的尺寸效应是产生柱状节理岩体水平和铅直原位试验各向异性的主要原因,随着承压板直径的增大,各向异性效应减小,当承压板直径大于6m后,柱状节理玄武岩体可视为各向同性体,研究成果对利用和改造柱状节理岩体具有较好的工程意义。     

Structural and electrical properties of single crystalline and bi-crystalline ZnO thin films grown by molecular beam epitaxy

C-oriented ZnO epitaxial thin films are grown separately on the a-plane and c-plane sapphire substrates by using a molecular-beam epitaxy technique. In contrast to single crystalline ZnO films grown on a-plane sapphire, the films grown on c-plane sapphire are found to be bi-crystalline; some domains have a 30o rotation to reduce the large mismatch between the film and the substrate. The presence of these rotation domains in the bi-crystalline ZnO thin film causes much more carrier scatterings at the boundaries, leading to much lower mobility and smaller mean free path of the mobile carriers than those of the single crystalline one. In addition, the complex impedance spectra are also studied to identify relaxation mechanisms due to the domains and/or domain boundaries in both the single crystalline and bi-crystalline ZnO thin films.     

激光探针等离子体质谱测定单颗粒锆石铀-铅年龄

建立了一种利用激光探针等离子体质谱测定单颗粒锆石Ｕ－Ｐｂ同位素年龄的新方法。以线扫描进样法代替传统的剥深进样法,克服Ｕ／Ｐｂ之间的熔蚀分异。对前寒武纪锆石的定年表明,＾２０７Ｐｂ／＾２０６Ｐｂ／＾２３８Ｕ定年精密度和准确度均为优于２％。     

冲击磨损下团球状共晶体奥-贝钢磨损表面层组织的变化

采用ＭＬＤ－１０型磨损试验机、扫描电镜和透射电镜等研究了冲击磨损条件下团球状共晶体奥－贝钢磨损表面组织的变化。结果表明：奥－贝钢的冲击磨损表层中存在非晶态组织和纳米级晶粒;磨损亚表层中存在大量位错马氏体和形变贝工体组织;奥－贝钢从亚表层到磨损表面方向的硬度逐渐增加,具有梯度分布特征,能够有效抵抗磨料的冲击和凿削作用,同时磨损亚表层中的位错、形变马氏体和贝氏体组织具有很好的强韧性匹配,可抑制高冲击下     

煤粉炉喷钙脱硫过程的总体模型与模拟

1前言我国燃煤中约有三分之一用于火力发电,减少火电厂SO。排放是治理酸雨和SO。污染的重中之重。炉内喷钙脱硫结合尾部增湿活化技术（LIFAC）因流程简单、投资省、运行费用低而且效率较高,特别适用于燃烧中、低硫煤锅炉的改造,是一种具有广泛应用前景的技术［1］本文?..     

Grain Boundary Resistivity and Electrically Induced Grain Boundary Migration (EIGM) in Metallic Bamboo Microstructures

As VLSI conductor line dimensions continue to decrease, electrotransport properties increasingly effect device lifetimes. Grain boundaries are intimately linked to these processes, providing paths of varying diffusivity, and as mobile defects themselves. Haessner et al. [6] make a challenging finding in experiments with thin gold films: based on calorimetric data, in order to account for the velocity of grain boundaries migrating in high electric current densities, the force on the atoms of a grain boundary would have to be two orders of magnitude larger than what the accepted theory for bulk ions predicts. The failure is attributed to the simplicity of the model which does not account for possible variations of the resistivity and effective valance charge that could occur in the vicinity of a grain boundary. In this paper, expressions are developed for the electron wind force on the atoms near grain boundaries, and they are written in terms of thermodynamic variables: the boundary specific volume expansion and specific resistivity. The enhancement of the wind force of the boundary atoms over the bulk wind force is calculated using published data. This model allows for more than an order of magnitude enhancement in gold, and Haessner's observation is rationalized.