Laser-stimulated compensation of bulk defects in p-CdZnTe

The data on the interaction of infrared laser radiation with ?ω?E _g and power density W, no higher than the thermal destruction threshold of low-resistivity p-CdZnTe crystals (4 ≤ ρ ≤ 25 Ω cm) are presented. It is shown that the laser-stimulated defects, until attaining a stable state, pass two nonequilibrium stages depending on the interaction time and W. During these stages, the crystal properties partially relax to the initial or the stable state, respectively. In the stable state, the optical transmittance (λ ≤ 20 μm) and resistivity attain values that satisfy the requirements to the CdZnTe substrates for the HgCdTe IR photodetectors. The laser-stimulated transformations in the lattice are considered using a model that attributes the generation of activated centers in a bulk and their migration to entrainment by free carriers in an electric field of the laser wave.     

Laser-stimulated modification of the impurity energy spectrum of gallium selenide intercalated with cobalt

The effect of laser radiation on the impurity energy spectrum of intercalated structures is studied by the example of 〈Co〉_0.015GaSe. By the variations in frequency dependences of resistivity measured normally to the layers of the obtained structure and by the transformation of the Nyquist diagrams consisting of two connected in series parallel R ‖ C units, a conclusion is made on the laser-stimulated compensation of the intercalant. The obtained values of the real part of permittivity are characteristic of doped semiconductors or their alloys in the radio-frequency range. The experimental results showed that the pulsed laser irradiation is an effective method to affect the energy impurity spectrum of intercalated compounds.     

发展路程

许多经营认为，在每节点500户的规模，成本与业务能力的平衡状况是令人满意的。但是，如果订户数量猛增，经营的平台必须能发展到更小的节点规模。根据系统升级与重建的初期投资费用，经营应考虑一个既能提高最终用户可靠性，     

原子共振滤波器研究的发展

介绍了原子共振滤波器的发展历史及研究进展情况,并指出了原子共振滤器的未来发展前景.     

The Mg atomic frequency standard

Recent advances towards the realization of an absolute frequency standard in the submillimeter region are reported. The³p1-³P_{0} Delta m_{j} = 0fine structure transition in the metastable triplet of²⁴Mg has been observed in an atomic beam with both Rabi and Ramsey interrogation techniques. Experimental results and theoretical predictions are compared and discussed in view of an Mg frequency standard.     

可输入气体及加热样品的高分辨原位电子显微镜及其应用

在材料科学和工业生产中,气态-固态相互作用是材料合成及处理过程中的基本环节之一,很多研究诸如纳米材料的生长、纳米材料对生态环境及生物组织的影响、催化剂的制备和催化过程,以及微量气体探测等都离不开对气态-固态反应的深入了解.随着纳米时代的来临,对气态-固态作用机制的研究也随之进入了原子分辨率的水平.所以样品室能够接受气体和根据需要对样品进行加热,并具备原子分辨率成像能力的透射电子显微镜就变得非常重要.本文旨在介绍应用日立300 kV H-9500型高分辨透射电子显微镜对不同材料进行原位电子显微术观察的技术,目的是研究固体材料与气体相互作用而产生的原子水平上的结构变化.日立H-9500型电镜具有较为独特的真空系统设计.一台高速涡轮分子真空泵与样品室连接使得气体可以不断被注入样品室又不断被快速抽出.在样品室的上方加装有一个小孔光阑,其作用是让电子束正常通过但大幅减少样品室中的气体向高真空的电子枪区域的扩散.在电子枪的下方设有一个真空测量装置,当从样品室泄漏过来的气体过多时,电子枪下方的一个阀门会自动关闭从而保护电子枪不被损坏.这台电镜既可以作为普通电镜用于结构研究和成分分析,需要时又可以用日立公司的'气体-加热样品台'将气体注入电镜样品室和对样品加热进行动态结构变化的高分辨研究.用这种电镜可以研究半导体材料、催化剂颗粒、纳米碳管、以及陶瓷材料.本文对部分研究结果进行了简略的介绍.     

Optically pumped atomic thulium lasers

A thulium vapor column is irradiated with the fourth harmonic of a Nd:YAG laser at 266 nm. The near coincidence with a dipole allowed transition from ground state results in efficient optical pumping yielding 87 simultaneous superfluorescent laser transitions from 300 to 900 nm. Many of the emissions are due to inversions to the ground state of both neutral and singly ionized Tm atoms.     

Limitations of atomic beam frequency standards

Atomic beam frequency standards may be placed into two categories: field standards and laboratory standards. While this distinction is somewhat artificial, because the two types of standards are interdependent, each category does have different requirements of accuracy, size, and cost. Despite this separation, generally the developments which produce the best laboratory standards eventually give rise to improved field standards. Existing field standards are limited in long term fractional frequency stability to σ_y (τ) 3 x 10^-13, for τ 6 months. A laboratory standard such as NBS-6, the U.S. primary cesium standard, is limited in inaccuracy to Δ_y 8 x 10^-14. Proposed new cesium field standards are expected to yield long term stabilities of σ_y(τ) 1 x 10^-14 (τ = 6 months). Stored ion standards, prime candidates for new laboratory frequency standards, are expected to have better than Δy = 1 x 10^-15 inaccuracy. As other approaches to atomic beam frequency standards are considered, they should attempt to compete favorably with these emerging technologies.     

Texture of atomic layer deposited ruthenium

Ruthenium films were grown by plasma enhanced atomic layer deposition (ALD) on Si(1 0 0) and ALD TiN. X-ray diffraction (XRD) showed that the as-deposited films on Si(1 0 0) were polycrystalline, on TiN they were (0 0 2) oriented. After annealing at 800 °C for 60 s, all Ru films were strongly (0 0 2) textured and very smooth. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) demonstrated that the lateral grain size of the annealed films was several 100 nm, which was large compared to the 10 nm thickness of the films. No ruthenium silicide was formed by annealing the ALD Ru films on Si(1 0 0). Comparison with sputter deposited films learned that this occurred because the ammonia plasma created a SiO_xN_y reaction barrier layer prior to film growth.     

CW laser action in atomic fluorine

We have obtained CW laser action on four transitions in the doublet system of atomic fluorine for the first time. All previously reported laser action was on a pulsed basis only. CW laser radiation was obtained when F2or AgF was used as a fluorine donor in an electron beam pumped helium plasma. A multiline output power of 200 mW was obtained.     

Refactoring for software migration

Refactoring can be an important ingredient in the strategy for development and evolution of complex telecommunications software systems. Refactoring is one way to reuse and extend a successful software system. This article presents some design tactics that will assist a development team when they choose evolution from an existing software system over building a completely new system from the ground up. Strictly speaking, the refactoring process changes only the internal design of the software. Refactoring does not add any new functionality. However, the goal of refactoring work is to pave the way for the software to be modified and extended more easily. The simplest example of redesign is the creation of simple “wrapper classes” that contain groups of functions extracted from the legacy code. More complex design patterns are also useful when attempting to improve the design. Developers usually divide the redesign work into stages so that each stage can be implemented and tested separately. This article describes a real-world example of this approach that shows how refactoring improved the design of a wireless base station controller product     

Vortex beams for atomic resolution dichroism

Vortex beams carrying orbital angular momentum have been produced recently with electron microscopy by interfering an incident electron beam with a grid containing dislocations. Here, we present an analytical derivation of vortex wave functions in reciprocal and real space. We outline their mathematical and physical properties and describe the conditions under which vortex beams can be used in scanning transmission microscopy to measure magnetic properties of materials at the atomic scale.     

A four-parameter atomic decomposition of chirplets

A new four-parameter atomic decomposition of chirplets is developed for compact and precise representation of signals with chirp components. The four-parameter chirplet atom is obtained from the unit Gaussian function by successive applications of scaling, fractional Fourier transform (FRFT), and time-shift and frequency-shift operators. The application of the FRFT operator results in a rotation of the Wigner distribution of the Gaussian in the time-frequency plane by a specified angle. The decomposition is realized by using the matching pursuit algorithm. For this purpose, the four-parameter space is discretized to obtain a small but complete subset in the Hilbert space. A time-frequency distribution (TFD) is developed for clear and readable visualization of the signal components. It is observed that the chirplet decomposition and the related TFD provide more compact and precise representation of signal inner structures compared with the commonly used time-frequency representations     

Active wavelength-shifting in atomic resonance filters

Active wavelength-shifting is described as a method to expand the number of wavelengths at which atomic resonance filters operate. Optical pumping and exoergic collisional energy transfer are shown to be powerful wavelength-shifting techniques. Expressions have been derived for internal photon conversion efficiency in limiting cases. They are cast in forms that suggest simple branching ratio model equivalents. The photophysical models yield important insights into methods to obtain good photon conversion for even strongly absorbing levels. The results are applied to atomic resonance filters operating at intense Fraunhofer wavelengths     

高速原子力显微术研究进展

自1986年发明原子力显微镜以来,它已成为材料、生物以及纳米科技等许多领域的重要工具。由于常规原子力显微镜成像速度缓慢,在动态过程观测、工业生产线原位测量以及高密度信息存储等领域的应用受到限制,因此发展高速原子力显微术近年来已引起国内外的高度关注。本文综述了高速原子力显微术关键技术(包括:微小探针、高速扫描器设计和控制方法)以及应用等方面的最近进展。     

原子力显微镜激光光路调整方法

ＣＳＰＭ 930ｂ型多功能扫描探针显微镜经常需要进行手动激光光路调整。该仪器使用说明书[1] 介绍的调整方法可操作性差、手续繁琐、过程冗长 ,且难以判断激光束是否准确照射到微悬臂针尖背面的镀金层上 ,往往造成误判而导致微悬臂针尖被撞断裂。而且 ,按照原有方法操作者需要长时间全神贯注观察激光斑 ,使用者眼睛极易疲劳甚至造成损伤。笔者使用该仪器过程中 ,对光路调整方法进行了大量试验 ,摸索出了一套操作方便 ,容易准确判断针尖位置的有效方法。现总结交流如下。调整方法ＣＳＰＭ 930ｂ扫描探针显微镜ＡＦＭ部分激光光路如图 1所示。…     

Experimental investigation of the atomic fluorine laser

The atomic fluorine laser, as produced by a fast pulsed discharge in He-NF3mixtures, is investigated experimentally. Total collisional quenching rates of He 2³S on NF3, BF3, CBrF3, CCIF3, CHF3, CF4, C2F6, CO2, SF6, and N2are reported. Upper limits for collisional quenching rates of He 2¹S, 2³P, and 2¹P atoms on NF3are determined. We conclude that energy transfer from excited neutral He to NF3is not the primary pumping mechanism in the He-NF3atomic fluorine laser.