Hall effect analysis of high purity p-type GaAs grown by metalorganic chemical vapor deposition

Variable temperature Hall effect and low temperature photoluminescence measurements have been performed on high purityp- andn-type GaAs grown at atmospheric pressure by metalorganic chemical vapor deposition. These high purity epitaxial GaAs layers were grown as a function of the arsine (AsH₃) to trimethylgallium (TMG) ratio (V/III ratio). The accurate quantitative assessment of the electronic properties of thep-type layers was emphasized. Analysis of the material focussed on the variation of the concentration of the shallow impurities for different V/III ratios. Surface and interface depletion effects are included to accurately estimate the concentration of impurities. The model of the merging of the excited states of the acceptor with the valence band is used to include the dependence the activation energy of the impurity on the acceptor concentration as well as on acceptor species identity. The characteristicp- ton-type conversion with increasing V/III ratio was observed in these samples and the reason for thep- ton-type conversion is that the background acceptor concentration of carbon decreases and the germanium donor concentration increases as the V/III ratio is increased.     

极性小分子对Ni/TiO_2核壳结构电流变液性能的影响

通过力学性能试验、形貌观察,重点研究电流变液的核壳微粒Ni/TiO2用Urea等极性分子修饰对电流变液性能、形貌的影响。结果表明,极性小分子可大幅提高电流变液的性能,对Ni/TiO2/Urea微粒存在一个Urea/Ti临界值,其值的质量分数为30%。     

The design of spin filter junction in zigzag graphene nanoribbons with asymmetric edge hydrogenation

Using the non-equilibrium Green’s function method combined with the density functional theory, we investigate the electronic transport properties of a heterostructure based on zigzag graphene, This heterostructure consists of H2–NZGNR–H and H–NZGNR–H. Results show that a perfect dual spin filtering effect can be realized with the parallel (P) and antiparallel (AP) magnetiesm configuration, and some magnetic domain walls (DW) at the interface between two component ribbons. The magnetic moments, DOS and PDOS, the transmission pathways and LDOS demonstrate that the edge of C–H2 bonds have important effects for magnetic and spin dependent transport properties compared to the edge of C–H bonds. Our results show that the H2–ZGNR–H/H–NZGNR–H heterostructure holds promise for magneto electronics devices which can keep steady properties when change the widths of the two component ribbons.     

Safety defect analysis and method study of data network

This paper cascades crash analysis and NS2 simulation analysis to study the network system hidden. It is combined with the theory of complex systems from the nodes and links in the network system vulnerability analysis. Firstly, we abstract complex network systems to the node and link network topology. And then we remove key nodes and link vulnerability analysis center between lines metrics to analyze the effect of the network functionality caused by node crashes or link crashes. Secondly, we construct a cascade collapse model, using NS2 simulation to study outside deliberate attack and simulation system failure analysis; and give the embodiment of cascading breakdown on the network function.     

深亚微米SOI工艺SoC设计中天线效应的消除

深亚微米SOI片上系统芯片(SoC)因其工艺特性,按照常规的布局布线(PNR)流程,出现了约一万个天线效应违规。介绍了一种在布局布线阶段不插入反偏二极管就可以消除大量天线效应违规的优化迭代流程。通过对天线效应的产生以及天线比率公式的分析,从线长和栅面积角度考虑天线效应的修复,结合自动布局布线设计工具SoC Encounter对这些因素的控制,可以在布局布线阶段消除天线效应的违规,并能与版图验证的结果保持一致。在一款通用抗辐照SoC芯片的设计中,应用该优化流程在布局布线阶段消除了设计中的天线效应违规,有效节约了芯片整体设计时间。     

精细表面下细小缺陷的磁光涡流成像实时探测

磁光涡流成像检测装置可实现精细表面下细小缺陷探测。在该装置中，通过物体表面上方的交流激励线圈实现传统的涡流感应，涡流所感应的磁场由法拉第效应来检测。为了实现表面下缺陷的检测目标，激光穿过安放在激励线圈中的特殊的磁光晶体，激光偏振方向在晶体中的旋转大小取决于检测区域磁场的大小，缺陷将使检测区域磁场分量发生变化并使偏振光的旋转角发生相应变化，通过一光学装置转化成“明”或“暗”图像，该光学装置由传统的显微镜、照明系统、偏振器和CCD图像传感器组成。给出了初步的实验探测结果。     

Photoluminescence characterization of the effects of rapid thermal annealing on AlGaAs/GaAs modulation-doped quantum wells

In this study, we describe the effects of rapid thermal annealing on the electrical and optical properties of modulation-doped quantum wells (MDQWs). The sheet carrier concentration in MDQW structures which have been annealed in contact with a piece of GaAs tends to decrease with increasing annealing time due to Si auto-compensation in the doped AlGaAs regions. The high energy cut-off point of 4.2 K PL spectra, which occurs at the Fermi energy, and the 77 K PL linewidth are accurate measures of sheet carrier density. These two parameters track variations in carrier density produced by annealing. Photoluminescence spectra also provide additional insight into annealing-induced changes such as Si migration, which causes a degradation in the mobility of the two-dimensional electron gas.     

A quantitative evaluation of time-independent and time-dependent deformations of lead-free and lead-containing solder alloys

A method to separate plasticity and creep is discussed for a quantitative evaluation of the plastic, transient creep, and steady-state creep deformations of solder alloys. The method of separation employs an elasto-plastic-creep constitutive model comprised of the sum of the plastic, transient creep, and steady-state creep deformations. The plastic deformation is expressed by the Ramberg-Osgood law, the steady-state creep deformation by Garofalo’s creep law, and the transient creep deformation by a model proposed here. A method to estimate the material constants in the elasto-plastic-creep constitutive model is also proposed. The method of separation of the various deformations is applied to the deformation of the lead-free solder alloy Sn/3Ag/0.5Cu and the lead-containing solder alloy Sn/37Pb to compare the differences in the plastic, transient creep, and steady-state creep deformations. The method of separation provides a powerful tool to select the optimum lead-free solder alloys for solder joints of electronic devices.     

Study of defect levels in CdTe using thermoelectric effect spectroscopy

We have studied the defect levels in as grown and post growth processed cadmium telluride (CdTe) using thermoelectric effect spectroscopy (TEES) and thermally stimulated current (TSC) techniques. We have extracted the thermal energy (E_th) and trapping cross section (σ_th) for the defect levels using the initial rise and variable heating rate methods. We have identified 10 different defect levels in the crystals. Thermal ionization energy values obtained experimentally were compared to theoretical values of the transition-energy levels of intrinsic and extrinsic defects and defect complexes in CdTe determined by first-principles band-structure calculations. On the basis of this comparison, we have associated the observed ionization levels with various native defects and impurity complexes.     

Electron mobility in n-doped zinc sulphide

A study of the mobility of n-doped wurtzite and zincblende ZnS is reported. We have determined nonequilibrium thermodynamic state of the ZnS—driven far away from equilibrium by a strong electric field—in the steady state. The dependence of the mobility (which depends on the nonequilibrium thermodynamic state of the sample) on the electric field strength is derived, which decreases with the strength of electric field. We analyzed the contributions to the mobility arising out of the different channels of electron scattering, namely, the polar optic, deformation, interactions with the phonons, and with ionized impurities. The case of n-ZnS WZ and ZB have been analyzed: as expected the main contribution comes from the polar-optic interactions in this strong-polar semiconductor. The other interactions are in decreasing order, the deformation acoustic and the one due to impurities.