激光束诱导电流法提取HgCdTe光伏探测器的电子扩散长度

由于得到HgCdTe扩散长度L_p的标准测试结构会损伤p-n结单元,实验中广泛采用激光束诱导电流（LBIC）提取的等效扩散长度L来代替L_p.本文通过二维数值模拟,分析了等效扩散长度L和扩散长度L_p 的关系.二者的比例关系为L/L_p=1.1,该基本关系不受器件的关键参数如掺杂浓度、载流子寿命、载流子迁移率等的影响.最后将激光束 关键词： 碲镉汞 激光束诱导电流 扩散长度     

Studies of minority carrier transport in ZnO

The temperature dependence of the minority carrier diffusion length and lifetime in bulk n-type ZnO was studied using Electron-Beam-Induced Current (EBIC) and cathodoluminescence (CL) techniques. The diffusion length was observed to increase exponentially over the temperature range from 25 to 125 C, yielding an activation energy of 45 ± 2 meV. A concomitant decrease of the cathodoluminescence intensity for the near-band-edge transition was also observed. The activation energy determined by optical measurements was 58 ± 7 meV. The larger minority carrier diffusion length and smaller luminescence intensity are attributed to the increased lifetime of non-equilibrium holes in the valence band at elevated temperatures. Carrier trapping on Li-related levels with activation energy 283 ± 9 meV is also addressed.     

微波反射光电导衰减法测少子寿命演示实验

采用微波反射光电导衰减法设计了测试少子寿命的演示实验装置.实验装置主要由脉冲激光源、微波发射接收和数据采集处理系统等部分组成.该实验可以直观地演示非平衡载流子随时间的衰减过程,定量给出少子寿命、扩散系数和扩散长度.     

Effective history length of the minority game

It is known that the memory is relevant in the symmetric phase of the minority game. In our previous work we have successfully explained the quasi-periodic behavior of the game in the symmetric phase with the help of the probability theory. Based on this explanation, we are able to determine how the history length affects the variance of the system in this paper. By using some particular types of fake history such as periodic type and random type, we determine how efficient the history length has been used in the standard game. Furthermore, the analysis on the effective history length strongly supports the result we proposed previously that there are three distinct phases in the minority game.     

Physical processes of current gain in InAs bipolar junction transistors

InAs bipolar junction transistors (BJTs), grown by molecular beam epitaxy, are reported with common emitter current gains (β's) as large as 400. The factors affecting the common emitter current gain have been studied by estimating the magnitudes of the base transport factor (α_T) and emitter injection efficiency (γ). This has been accomplished by studying a sequence of InAs BJTs with varying emitter doping densities, N_E. Minority carrier diffusion length in the base (L_B), α_T, and γ have been extracted from measured electrical characteristics. The results of the study of these InAs BJTs are as follows: L_B≈0.4 μm, α_T≈98% and γ ranges from 92% to nearly 100% depending on N_E. This knowledge of the magnitudes of the injection efficiencies suggests when it would be useful to move from the simple BJT structure to the more advanced heterojunction bipolar transistor (HBT) structure. Lower γ BJTs would be improved, however high-γ BJTs would benefit little, by the use of the widegap emitters of HBTs. The method developed here to estimate γ, α_T and L_B is not specific to InAs BJTs, but should be useful for study of BJTs and HBTs in any material system.     

Effect of Gamma Radiation on the IR-Spectra of Polymethylmethacrylate

The IR-spectra of polymethylmethacryate (PMMA) have been measured before and after irradiation in air, in the region of wave number 700–4000 cm^?1. The results showed that the rate of decrease in the absorbance of the IR absorption bands correlated with the type of bond, and the type of vibration whether being stretching, bending or rocking one.

Es wurden die IB-Spektren von Polymethylmethacrylat vor und nach Bestrahlung mit Gammastrahlen in Luft im Wellenzahlbereich von 700 — 4000 cm?1 untersucht. Die Ergebnisse zeifgten, daβ die Geschwindigkeit der Abnahme der IR-Absorptionsbanden mil der Art der Bindung korreliert werden konnten und mit der Art der Schwingung, ob Streck-, Deformations- oder Schaukelschwingung.     

Modified nodal point method for the measurement of the large focal length of lenses

Some modifications have been suggested to the nodal slide and microscope method to suit the focal length measurement of large focal length lenses. In this procedure, the experimental set-up has to be accommodated on the two usual optical benches in line, and the position of the nodal point of the lens under test is easily located by introducing an extra lens of comparatively shorter focal length between the test lens and microscope. The results of the measurement of ‘f’ for a few lenses, and the experimental parameters, are presented.     

Effect of Gamma Radiation on the IR-Spectra of Polystyrene

The IR absorption spectra of both unirradiated and gamma irradiated polystyrene films were investigated. It was found that the intensities of IR absorption bands decreased exponentially with increasing radiation dose. The rate of decrease k was found to depend on the type of vibration and type of bond.

Es wurden die IB-Spektren von niehtbestrahUen, und mitGammaslrahlung bestrahlten Polystyrolfilmenuntersucht. Es wurde gefunden, daβ die Intensität der IR-Absorptionsbanden exponentiell bei ansteigenden Straldendosen abnimmt. Die Geschwindigkeit der Abnahmc(k) ist dabei abhängig vom Typ der Schwingung und damit vom Typ der chemischen Bindung.     

飞秒光频梳的任意长绝对测距

高精度测距在工业、航空航天、科学研究等方面都具有重要应用, 而不断发展的激光测距技术始终处于前沿研究领域. 本文研究飞秒光频梳绝对测距技术, 拓展光梳在长度测量领域的应用. 在利用脉冲激光进行任意绝对长度测量中常用到飞行时间法, 然而其测量分辨力受限于电子器件的带宽, 仅为毫米量级. 为克服这一缺点, 本文研究了光梳多脉冲序列之间的时间相干性, 结合多脉冲序列干涉法和飞行时间法提出了任意长绝对测距的方法, 搭建了基于改进型Michelson干涉原理的任意绝对测长系统, 通过同时测量多脉冲序列的一阶和二阶互相关信号, 可以分别计算出飞行时间的时间差, 即可得到被测距离. 利用光梳作为光源进行了0.6m的绝对测距实验, 将测量结果与高精度激光位移传感器的测量值进行比较, 实验结果表明本系统具有良好的测量线性度, 并且测距精度可达±0.5μm. 关键词： 飞秒光频梳 任意长绝对测距 飞行时间法 多脉冲序列干涉法     

Gradient plasticity for thermo-mechanical processes in metals with length and time scales

A thermodynamically consistent framework is developed in order to characterize the mechanical and thermal behavior of metals in small volume and on the fast transient time. In this regard, an enhanced gradient plasticity theory is coupled with the application of a micromorphic approach to the temperature variable. A physically based yield function based on the concept of thermal activation energy and the dislocation interaction mechanisms including nonlinear hardening is taken into consideration in the derivation. The effect of the material microstructural interface between two materials is also incorporated in the formulation with both temperature and rate effects. In order to accurately address the strengthening and hardening mechanisms, the theory is developed based on the decomposition of the mechanical state variables into energetic and dissipative counterparts which endowed the constitutive equations to have both energetic and dissipative gradient length scales for the bulk material and the interface. Moreover, the microstructural interaction effect in the fast transient process is addressed by incorporating two time scales into the microscopic heat equation. The numerical example of thin film on elastic substrate or a single phase bicrystal under uniform tension is addressed here. The effects of individual counterparts of the framework on the thermal and mechanical responses are investigated. The model is also compared with experimental results.     

大气相干长度测量中几个关键技术指标的分析

为规范大气相干长度的测量,保证测量数据的准确性,通过对大气相干长度测量中采样频率、采样时长、曝光时间等关键问题的分析,并结合国内外相关研究成果,确定了差分像运动测量仪的采样频率应不低于100 Hz、采样时长应不短于20 s ,单帧图像曝光时间应不长于沿测量光路的格林伍德时间常数,样本数应不少于2 000帧。     

莫尔偏折法测透镜焦距中的条纹二值化方法

当用莫尔偏折法测量透镜焦距时,条纹区域随着被测透镜和系统光学参数的不同而变化。针对此情况提出了确定条纹有效区域和选择二值化阈值的方法。该方法根据条纹图像数据的行列极值确定条纹的有效区域。介绍了该方法的实现过程,并分析了在有效区域内根据图像数据的灰度直方图自动选择二值化阈值的原理。给出了依据该方法提取条纹的示意图,以及用莫尔偏折法测量透镜焦距的实验结果。     

激光热透镜焦距测量实验及其公式改进

通过平平非稳腔法对激光热透镜焦距进行了实验测量,研究了不同抽运光束腰位置对热透镜焦距的影响.从理论上引入抽运光远场发散角和束腰位置,对端面抽运激光晶体热透镜焦距公式进行了改进.     

Diffusion of Ag through Se and its effect on interferometric thickness measurement

The effect of diffusion of silver through Se thin films, on the visibility of two and multiple beam interference fringes has been studied. For thickness measurements, Al has been found to be a suitable overcoating metallic layer as it does not diffuse through Se. The thickness was measured by multiple beam fringes at reflection.     

Photoelectric effect in some alloys in the region of absorption edges

Summary Photoelectric effect in alloys using the transmission method in the energy range (17.8÷138) keV, at energies in the region of absorption edges of the various elements in the alloys, have been measured and compared with the respective theoretical estimates.     

间接驱动的内爆不对称性随腔长和时间变化的研究

在激光间接驱动惯性约束聚变中, 为达到高密度压缩以实现点火, 对靶丸内爆对称性和黑腔辐射场均匀性有严格的要求. 为了研究内爆不对称性随腔长和时间的变化, 实验中采用了三种不同尺寸的黑腔, 利用X光分幅相机观测了靶丸燃料区自发光, 获得了压缩变形过程和椭圆度变化规律, 初步判断了在三种腔型中腔长1700 μm 的黑腔较接近神光Ⅲ原型装置内爆对称性要求. 根据视角因子程序计算得到辐射流不对称性随时间变化情况, 通过一个简化的解析模型推导出内爆形变不对称性随时间变化过程, 与实验结果大致符合. 由此进一步分析了黑腔辐射场不均匀性的演化导致内爆不对称性随腔长和时间变化的物理机制. 关键词： 内爆不对称性 黑腔辐射场不均匀性 腔长 视角因子程序     

Modified nodal point method for the measurement of the focal length of divergent lenses

The well-known nodal point method has been employed with some modification to measure the focal lengths of divergent lenses. In this modification, a telescope was used to locate precisely the nodal/principal point of the lens under test, and a travelling microscope was employed to locate precisely the focal point of the lens as well as to measure the focal distance. The accuracy of the measurement was found to be ± 0.5%, with the focal length of the order of about 10 cm.     

变悬点变摆长单摆运动分析

用两种方法导出了变悬点变摆长单摆的加速度和运动微分方程，分析了小球作周期振动的条件，讨论了角速度最大值的位置，并通过计算机数值计算，画出了小球作周期振动时的相图。     

Effect of High-Temperature Structure and Diffusion on Grain-Boundary Diffusion Creep in fcc Metals

Molecular dynamics simulations of high-energy twist and tilt bicrystals of fcc palladium reveal a universal, liquid-like, isotropic high-temperature diffusion mechanism, characterized by a rather low self-diffusion activation energy that is independent of the boundary type or misorientation. Medium-energy grain boundaries exhibit the same behavior at the highest temperatures; however, at lower temperatures the diffusion mechanism becomes anisotropic, with a higher, misorientation-dependent activation energy. Our simulations demonstrate that the lower activation energy at elevated temperatures is caused by a structural transition, from a solid boundary structure at low temperatures to a liquid-like structure at high temperatures. We demonstrate that the existence of such a transition has important consequences for diffusion creep in nanocrystalline fcc metals. In particular, our simulations reveal that in the absence of grain growth, nanocrystalline microstructures containing only high-energy grain boundaries exhibit steady-state diffusion creep with a creep rate that agrees quantitatively with that given by the Coble-creep formula. Remarkably, the activation energy for the high-temperature creep rate is the same as that characterizing the universal high-temperature diffusion in high-energy energy bicrystalline grain boundaries.     

Comparing Diffusion Approximation with Radiation Transfer Analysis for Light Transport in Tissues

The diffusion model that is an approximation of the equation of radiation transfer is typically used to describe photon migration in scattering-dominant media. In general biological tissue is highly scattering and very weakly absorbing against near-infrared light, yet it is heterogeneous and may contain relatively highly absorbing or low-scattering regions. Here applicability of the diffusion approximation over the radiative transfer theory for describing ultrafast laser transport in biological tissues is numerically studied and investigated over different kinds of tissue conditions and geometries. Tissues having tumors of different sizes, locations and nature as well as dual-tumor and low-scattering conditions are considered. Radiation transfer analysis is taken as a comparison objective and it is initially proved to be accurate in benchmark comparisons with Monte Carlo simulation. The results predict systematically about the compatible conditions where and when we can use the diffusion approximation and the conditions in which the diffusion approximation may provide misleading results.