Removal of oxygen from silicon by electron beam melting

Small amounts of multicrystalline silicon were melted in an electron beam furnace in different experimental conditions in order to investigate the oxygen evaporation behavior during the electron beam melting (EBM) process. The oxygen content level before and after EBM was determined by secondary ion mass spectroscopy. The oxygen content was reduced from 6.177 to 1.629 ppmw when silicon was melted completely at 15 kW with removal efficiency up to 73.6 %. After that, it decreased continually to <0.0517 ppmw when the refining time exceeded 600 s with a removal efficiency of more than 99.08 %. During the melting process, the evaporation rate of silicon is 1.10 × 10^?5 kg/s. The loss of silicon could be reduced up to 1.7 % during oxygen removal process to a desirable figure, indicating EBM is an effective method to remove oxygen from silicon and decrease the loss of silicon.     

Evolution analysis of the states of the EZ model

Based on suitable choice of states, this paper studies the stability of the equilibrium state of the EZ model by regarding the evolution of the EZ model as a Markov chain and by showing that the Markov chain is ergodic. The Markov analysis is applied to the EZ model with small number of agents, the exact equilibrium state for N = 5 and numerical results for N=18 are obtained.     

The structure and optical characters of the ZnO film grown on GaAs/Al2O3 substrate

In this paper ZnO films are grown on GaAs/Al₂O₃ substrates at different temperature by metal-organic chemical vapor deposition (MOCVD). The GaAs/Al₂O₃ substrates are formed by depositing GaAs layer (∼35 nm) on the Al₂O₃ substrate. The results of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) demonstrate that most of the Ga and As atoms form Ga-As bond and the GaAs layer does not present any orientation. The characters of the ZnO films grown on GaAs/Al₂O₃ substrates are investigated by XRD, photoluminescence (PL), atomic force microscopy (AFM) and Raman scattering. Compared with ZnO film grown on Al₂O₃ substrate, ZnO film prepared by our fabrication scheme has good crystal and optical quality. Meanwhile its grain size becomes bigger according to the AFM image. Raman analysis indicates that the intrinsic defects and the in-plane tensile stress are obviously reduced in ZnO/GaAs/Al₂O₃ samples.     

Structural, optical, and electronic properties of colloidal CuO nanoparticles formed by using a colloid-thermal synthesis process

Colloidal cupric oxide (CuO) nanoparticles were formed by using a colloid-thermal synthesis process. X-ray diffraction patterns, transmission electron microscopy (TEM) images, high-resolution TEM images, and X-ray energy dispersive spectrometry profiles showed that the colloidal CuO nanoparticles were formed. The optical band-gap energy of CuO nanoparticles at 300 K, as determined from the absorbance spectrum, was 3.63 eV. A photoluminescence spectrum at 300 K showed that a dominant emission peak appeared at the blue region. X-ray photoelectron spectroscopy profiles showed that the O 1s and the Cu 2p peaks corresponding to the CuO nanoparticles were observed.     

以最大原子密度定义合金相中的第一近邻团簇

本文提出利用不同壳层所包含的径向原子密度, 即单位体积内的原子个数随着径向的分布, 来方便而精确地定义团簇, 即具有最大径向原子密度的且表面呈现三角密堆结构的完整壳层为第一近邻团簇. 最后以Al-Ni-Zr合金相为例说明了该方法的合理性与适用性, 及此方法所定义的团簇与非晶形成的关系.     

窗口可变滑动相关分析方法在激光诱导击穿光谱谱线自动识别中的应用

激光诱导击穿光谱(LIBS)谱线具有很窄的展宽,且光谱仪因外界温度条件的变化存在波长漂移,光谱数据为离散数字信号,受噪声、谱线重叠及连续背景的影响,信号存在失真和变形。而目前光谱仪自带谱线识别分析软件主要以"就近原则"为主,错误率较高,必须依赖于人眼的观察对比。针对这个问题,在研究LIBS光谱特性的基础上,提出了一种窗口可变滑动相关分析方法(CAASW),用于激光诱导击穿光谱谱线自动识别。以土壤标准物质为样品,对该方法进行了实验分析和评价,与光谱仪自带分析识别软件相比,CAASW明显提高了识别准确率和识别速度,最终实现了谱线的自动识别。     

板条增益介质波前畸变诊断方法

对波前重构算法中的区域法进行了改进,使其能够应用于板条增益介质的波前畸变诊断。利用该方法对47块Nd: YAG板条增益介质沿厚度方向波前畸变进行测量,指出镀膜和加工等环节对增益介质的波前畸变可能造成的影响。按照波前畸变峰谷（PV）值对测量结果进行了统计,结果表明:增益介质造成的静态波前畸变参差不齐,测量样本中静态畸变PV值最多可达5 m以上,且仅有4.1%的增益介质静态畸变PV值小于1 m。通过选取某些增益介质使之级联,测量其组合波前畸变,发现在系统中使用两块波面互补的增益介质有助于减小系统的静态波前畸变。     

Boson peak in Sm-Al-Co ternary metallic glasses and its possible structural origin

The low temperature specific heat of Sm-Al-Co ternary metallic glasses is investigated and a clear anomaly associated with the Boson peak is identified. While this anomaly depends slightly on the chemical composition, it has no dependence on external magnetic field. To figure out the mechanism of the Boson peak, we interpret the data within various model frameworks. Unlike earlier work, our study shows that this Boson peak is mainly ascribed to an additional T² term of the specific heat, which may originate from the quasi-two-dimensional and short-range ordered structure units possibly existing in the metallic glasses.     

A scanning superconducting quantum interference device microscope for room temperature samples

We have constructed a scanning low-T_c superconducting quantum interference device (SQUID) microscope, in which the SQUID is mounted on the lower end of a copper rod and cooled to liquid helium temperature. There is a 65μm thick sapphire window under the SQUID. The sample at room temperature underneath the window can be scanned to produce magnetic images. The microscope has a spatial resolution of 100－150μm and a magnetic field sensitivity of 3－60pT/$\sqrt{Hz}$ in a magnetically unshielded environment. We have used this scanning SQUID microscope to measure various room temperature samples.     

Observation of D+(s)K- and evidence for D+(s)pi- final states in neutral B decays

We report the first observation of a B meson decay that is not accessible by a direct spectator process. The channel B(0)-->D(+)(s)K- is found in a sample of 85 x 10(6) BB; events, collected with the Belle detector at KEKB, with a branching fraction B(B(0)-->D(+)(s)K-)=(4.6(+1.2)(-1.1)+/-1.3) x 10(-5). We also obtain evidence for the B0-->D(+)(s)pi(-) decay with branching fraction B(B0-->D(+)(s)pi(-))=(2.4(+1.0)(-0.8)+/-0.7) x 10(-5). This value may be used to extract a model-dependent value of |V(ub)|.