Photo-induced ESR and optical absorption edge shift in amorphous Ge-S films

Reversible shift of the optical absorption edge by the cycle of band-gap illumination and annealing has been observed for Ge-S films for the first time. Photo-induced ESR has been observed, and it is explained by two processes: (1)Increase in randomness of the structure by illumination, and (2)Trapping of free carriers excited by illumination by charged dangling bonds. The ESR signal caused by the former process does not disappear either by warming the film up to room temperature or by illuminating it with the mid-gap light, while that by the latter process disappears.     

反应离子镀光学薄膜的微观结构分析

用反应离子镀方法制备了ＴｉＯ２单层膜及ＴｉＯ２／ＳｉＯ２多层膜，用透射电子显微镜分别观察了由反应离子镀方法及传统蒸镀法二种不同工艺制得的ＴｉＯ２单层膜及ＴｉＯ２／ＳｉＯ２多层膜的断面结构，并对ＴｉＯ２单层膜进行了喇曼分析和卢瑟福背散射分析。     

A theory of the diffraction of an electromagnetic wave by a plane screen

The problem of the diffraction of an arbitrarily polarized electromagnetic plane wave by a perfectly conducting plane screen of infinitesimal thickness is reduced to scalar problems by the method known from earlier papers. The wave field diffracted either by a screen of infinite extent which is perforated by an aperture of arbitrary size and shape or by a complementary screen is then described by means of the bra-vectors, ket-vectors and linear operators introduced by the present author in one of his preceding papers.     

稀土元素(La,Y)掺杂GaN的第一性原理计算

采用基于密度泛函理论的第一性原理赝势平面波方法,对稀土元素La,Y单掺杂和La和Y共掺杂GaN的晶格常数、电子结构及光学性质进行了计算与分析.计算结果表明:掺杂改变了GaN的能带结构,未掺杂和Y掺杂形成导带底和价带顶位于G点的直接带隙半导体,而La掺杂和La和Y共掺杂形成导带底位于G点,价带顶位于Q点的间接带隙半导体.可以通过掺杂元素来调制GaN的禁带宽度和带隙类型,掺杂均提高GaN在低能区的静态介电常数、反射率、折射率,使光子的跃迁强度增大,说明稀土元素La,Y掺杂可有效调制GaN的光电性质.     

Meeting Reports

From the Introductory Course in Saclay to ECNS 2005 in Montpellier, by Joel Mesot Magnetism and Progress in Superconductors, by Stephane Raymond Chemical Structure and Dynamics, by Don Kearley Industrial and Medical Applications, by P. Allenspach Section Instruments and Methods, by Helmut Schober Soft Matter, by Arantxa Arbe Fundamental Physics with Neutrons, by Tyno Abdul-Redah and C. Aris Chatzidimitriou-Dreismann Disordered and Frustrated Systems, by Reiner Zorn Neutrons and Life Science, by Stephane Longeville Mecasens 2003 Comes to Manchester, by Sue Edwards Oxford Summer School Takes Place in September 2003, by Gerry Lander KEK and JAERI Host IPN2003, by Masatoshi Arai UKJ2003 Held in Japan, by Uschi Steigenberger     

核酸碱基的付立叶变换红外拉曼光谱特征

本文给出了核酸碱基付立叶变换红外（ＦＴ—ＩＲ）激光拉曼光谱特征，并与可见光激光拉曼光谱进行了比较。结果表明，付立叶变换红外激光拉曼获得较可见光激光拉曼光谱波数范围更宽（低波数）的谱带范围，所获谱图荧光干扰小，谱图质量明显高于普通激光拉曼光谱谱图。     

Low-energy neon-ion scattering and neutralization on first and second layers of a Ni(001) surface

The scattering and neutralization of 2.4 and 5 keV Ne⁺ ions on the Ni(001) surface have been studied by time-of-flight (TOF) and electrostatic analyzer (ESA) techniques. The scattering yield of neutrals plus ions (by TOF) is strongly dependent on crystal orientation, in one direction being reduced by the shadowing of 2nd layer atoms by 1st layer atoms, or in another being increased by focussing of ions onto the 2nd layer by 1st layer atoms. Ion yields (by ESA) show little of this variation since the ions are largely neutralized on scattering from the second layer. The results thus demonstrate and explain the first layer selectivity of low-energy ion scattering by ESA for a case in which there is no shadowing of second layer atoms by the first layer. On the other hand, the ability to measure and distinguish first and second layer scattering of neutrals and ions by TOF suggests the possibility of composition analysis of individual layers of single crystal alloys and compound semiconductors.     

Specification of spectral line shape and multiplex dispersion by self-imaging and moiré technique

Due to finite width of a spectral line, the visibility of the moiré fringes formed by a grating and the self-image of another similar grating reduces by the increase of the self-image order. This effect is exploited to specify the spectral line shape by evaluating the Fourier transform of a function related to the visibility. Even, by using in-expensive optics, the technique can provide the spectral line shapes of rather broad widths—of the order of nanometer and more—by precisions that are comparable by those obtained by expensive Fourier transform spectrometers.Besides, it is shown that by comparing the line shapes obtained with and without a dispersive medium between the gratings, one can specify the dispersion function of the medium in the wavelength range covered by the spectrum.     

Scholte Wave at Air-Metal Interface Generated by a Pulsed Disc-Like Source

The normal displacement and pressure of Scholte and Leaky Rayleigh waves at air-metal interface generated by a pulsed disc-like source are simulated theoretically by the Cagniard-de Hoop method and studied by laser ultrasound technique experimentally. It is found that the Scholte wave detected by a photorefractive interferometer is mainly contributed by the surface pressure and the Leaky Rayleigh wave is dominated by the surface displacement. It is also proven that the pulse width of these interface waves is mainly determined by the acoustic time delay on the generating source size under our experimental conditions.     

General theory for the ferroelectric polarization induced by spin-spiral order

The ferroelectric polarization of triangular-lattice antiferromagnets induced by helical spin-spiral order is not explained by any existing model of magnetic-order-driven ferroelectricity. We resolve this problem by developing a general theory for the ferroelectric polarization induced by spin-spiral order and then by evaluating the coefficients needed to specify the general theory on the basis of density functional calculations. Our theory correctly describes the ferroelectricity of triangular-lattice antiferromagnets driven by helical spin-spiral order and incorporates known models of magnetic-order-driven ferroelectricity as special cases.     

Progress in Ultrasonic Spray Pyrolysis for Condensed Matter Sciences Developed From Ultrasonic Nebulization Theories Since Michael Faraday

This review outlines, in great detail, the history of the phenomenon of ultrasonic nebulization of liquids since the discovery of such an effect by Michael Faraday and the explanation of the phenomenon by capillary wave mechanism and “cavitation” hypothesis. Capillary waves described by the Kelvin equation are confirmed by Lang's experiment and more theoretical models by Peskin & Raco and Jokanovic. Cavitation bubbles have been elaborated by the Rayleigh-Plesset equation as well as the correlation equations between predicted and experimentally measured droplet diameter. Correlation equations such as one by Rajan & Pandit and Avvaru et al. have been considered. Ultrasonic spray pyrolysis for materials processing and the theories that predict the final particle size distribution are introduced. The popularity of the technique is shown by the rising number of research groups in the world processing various materials by this method due to its cost-effectiveness, purity of its products, and controllability of particle size as well as final properties.     

激光协同聚焦超声辐照生物样品增强热效应的实验和理论研究

对中等强度聚焦超声在生物样品中产生的热效应以及激光协同超声增强热效应进行了实验和理论研究。实验上,对生物和仿生样品在超声作用和激光协同超声作用下加热情况进行测量,通过对比表明,激光协同超声作用于生物样品,引起空化效应以及温度升高更为明显。同时,理论上对聚焦超声在生物样品中衰减产生的热效应、超声空化以及激光协同超声增强空化及其产生热效应进行机理分析。通过对机理的分析表明,激光引起的光致核化使超声空化更易于产生,有效的增强空化效应,进而增强热效应。为对具体实验给出量化分析和估算,通过理论与实验结果相拟合,对超声传播引起的温度升高进行计算,并估算超声和激光协同超声产生空化微泡对加热效应的不同贡献,为空化效应在超声治疗中的贡献提供参考数据。      

Surface modification of TA2 pure titanium by low energy high current pulsed electron beam treatments

Surface integrity changes of TA2 pure titanium including surface topography, microstructure and nanohardness distribution along surface layer were investigated by different techniques of low energy high current pulsed electron beam treatments (LEHCPEBTs). The surface topography was characterized by SEM. Moreover, the TEM observation and X-ray diffraction analysis were performed to reveal the surface modification mechanism of TA2 pure titanium by LEHCPEBTs. The surface roughness was modified by electron beam treatment and the polishing mechanism was analyzed by studying the cross section microstructure of electron beam treated specimens by SEM and TEM. The results show that the surface finish obtains good polishing quality and there is no phase transformation but the dislocations by LEHCPEBT. Furthermore, the nanohardness in the surface modified layer is improved. The remelt and fine-grain microstructure of surface layer caused by LEHCPEBTs are the main polishing mechanism and the reason of modification of surface topography and the increment in nanohardness is mainly due to the dislocations and fine grains in the modified layer induced by LEHCPEBT.     

The rigorous electromagnetic theory of the diffraction of vector beams by a circular aperture

The rigorous electromagnetic theory of the diffraction of vector beams by an aperture is proposed and numerically evaluated by the diffraction of vector Gaussian beams by a circular aperture. The results are compared with those, by using the vector Rayleigh–Sommerfeld diffraction integrals and angular-spectrum expression theory, showing a good consistency. The numerical calculation shows that the result calculated by the rigorous theory is much more precise than those calculated by the integral method in diffraction near field, and a highly consistency reaches by the three methods in diffraction far field. A further extension of the theory is discussed.     

实时全息术检测透明物的一种新方法

介绍了实时全息术检测透明物的一种新方法,它采用物光再现的参考光和参考光通过全息图的直透光所形成的干涉图纹检测透明物体的变化。证明了这组干涉图纹与用参考光再现的物光和物光通过全息图的直透光所形成的干涉图纹分布规律相似,仅在相位上相差π。还讨论了这组干涉图纹的衬比和获得最佳衬比的条件。此方法可消除物光光路上某些因素带来的相位畸变,避开待测物体自发光的干扰,并可在全息图后方任意位置进行记录,这使实时全息术在实践中更具有灵活性,有助于它在更广阔领域内的应用。     

碳化硅反射镜坯体光学加工的残余应力测量与分析

测量并分析了碳化硅反射镜坯体光学加工的残余应力。采用X射线衍射法测定了磨削成形、研磨以及抛光过程引入的表面残余应力的性质和大小;采用逐层抛光法测定了在用120#粒度金刚石砂轮磨削时引入的残余应力层厚度。研究结果表明:在用120#金刚石砂轮磨削加工时沿磨削方向和垂直于磨削方向分别引入了残余拉应力和残余压应力,其大小分别为40MPa和70MPa,应力层深度约为60μm,大于裂纹层深度;在用W7金刚石微粉研磨时引入了残余压应力,在其作用范围内残余应力平均值为60～80MPa;在抛光时理论上会引入残余压应力。在此基础上提出了在碳化硅反射镜坯体的光学加工过程中,可以通过研磨消除磨削引入的裂纹层和残余应力层。     

Meeting Reports

African Neutron Diffraction Meeting Held in South Africa, by Andrew Venter Faraday Prize Awarded at BIW04, by Myra Fultz, Tom Shea, Coles Sibeley, and Charlie Horak American Conference on Neutron Scattering Deemed a Success, by C. F. Majkrzak and R. Cappelletti Third Sample Environment Workshop Reviewed, by Ian Bailey New Perspectives in Neutron and Muon Science Meets in Warwick, by Mark Telling Neutron and Muon Meeting Provides a Forum for Users, by Mark Telling Gen Shirane and the Frontiers of Neutron Scattering, by Steve Shapiro     

Nuclear spin conversion of methane in pure and rare-gas mixed crystals

Spin species conversion has been observed by means of neutron scattering. Methane, matrixisolated in rare-gas crystals has been investigated by measuring the time dependence of the detailed balance factor of inelastic neutron spectra. The temperature dependence of conversion rates in the interval between 2 and 5 K turns out to be stronger than predicted by a single phonon process. In general, conversion times are of the order of hours in this temperature region. The influence of the matrix is well described by a coupled phonon density of states. Crystals of pure and krypton doped methane have been examined by measuring the time dependence of the total neutron scattering cross section. For pure methane, the temperature dependence of the conversion rates shows two regimes for both free rotator and ordered molecules. Below 5 K, the behavior is described by a single phonon process and above by an Arrhenius law. Rates are enhanced by krypton dotation, which is explained by changed level spacings due to orientational disorder.     

Ion extraction and charge exchange in laser isotope separation

In the atomic vapor laser isotope separation (AVLIS) process, a vapor is ionized by pulsed laser beams, and the ions are extracted by negatively biased collectors. We compute the unsteady dynamics of the photoplasma using a two-dimensional (2-D) particle-in-cell (PIC) code. Collisions between ions and neutral species are simulated by a Monte Carlo technique. The plasma dynamics is visualized by snapshots of particle positions showing the directions of their velocities. The three kinds of particles (electrons, photo-ions, and ions created by charge exchange) are marked by different colors. The graphic outputs illustrate the motion of the electrons toward the anodes, the vertical drift of the plasma, its erosion by the transient ion sheath, and nonselective ionization by charge exchange     

化学水浴法和磁控溅射法制备硫化镉薄膜的性能研究

以氯化铵、氯化镉、氢氧化钾和硫脲为反应物采用化学水浴法制备了硫化镉薄膜,为了作对比研究,采用射频磁控溅射以硫化镉为靶材,氩气为溅射气体,制备了硫化镉薄膜。采用X射线衍射、扫描电子显微镜和紫外-可见光光谱仪分别表征了硫化镉薄膜的结构、形貌和光学吸收特性。结果表明,采用以上两种方法制备的硫化镉均具有(002)择优取向,溅射法制备的硫化镉薄膜较致密,薄膜表面较光滑,平均晶粒尺寸在20～30nm;水浴法制备的硫化镉薄膜颗粒尺寸较小,缺陷较多。除了在短波段溅射所得硫化镉薄膜的透过率略差于水浴法所得硫化镉薄膜之外,溅射法制备的硫化镉薄膜的性能整体上优于水浴法制备的薄膜。两种方法制备的硫化镉薄膜的能隙在2.3～2.5eV。