Ferromagnetic order and critical behavior at surfaces of ultrathin epitaxial films

The critical behavior, ferromagnetic order and magnetic anisotropies of ultrathin, epitaxial, magnetic films is studied using electron capture spectroscopy (ECS), which is capable of probing the long-ranged and short-ranged electron spin polarization (ESP) at the topmost surface layer of uncoated and coated magnetic structures. For all systems [Ni(100)/Cu(100), Ni(100)/NaCl(100), fcc Fe(111)/Cu(111), Fe(100)/Ag(100), Tb/Fe(100)/Ag(100), Fe(100)/Au(100), hcp Tb(0001)/W(110), Fe(110)/W(110), V(100)/Ag(100), Pd(100)/Ag(100), Pd/W(110)] investigated so far, ferromagnetic order is detected. It is found that the surface Curie temperatureT _Cs depends on film thicknessd. ECS data obtained at the surface of various systems reveal the existence ofT- andd-dependent magnetic anisotropies. Although for V(100)/Ag(100) the measured critical exponent=0.128 agrees very well with=1/8 predicted for the two-dimensional Ising model, for other systems, such as Fe(100)/Au(100), the measured value (0.25) is in disagreement with theoretical predictions. The experimental results are discussed within the framework of presently available experimental and theoretical data.     

内混合气溶胶粒子体系有效吸收系数的计算

分析了以黑碳和水组成的内混合强吸收气溶胶粒子体系有效吸收系数随时间变化的规律,并讨论了不同波长、不同半径比等对有效吸收系数的影响。结果表明:波长越短,内混合气溶胶粒子体系有效吸收系数越大,在1~100 s内随时间增大的速度也越快,1~100 s内的增幅比100~1000 s内的大,最大增幅达到132.65%;不同的内外半径比对内混合气溶胶粒子体系的有效吸收系数有较大影响,内外半径比越大,有效吸收系数越大,在1~100 s有效吸收系数增加速度越快,1~100 s内增幅较大,最大增幅达到138.66%。     

Mass measurements far from stability around theN=Z line (100Sn,100In,100Cd)

Secondary ions of¹⁰⁰Ag,¹⁰⁰Cd,¹⁰⁰In and¹⁰⁰Sn were produced via the fusion-evaporation reaction⁵⁰Cr+⁵⁸Ni at an energy of 5.1 MeV/nucleon. TheA=100 secondary ions were accelerated in the second cyclotron of GANIL, which was used as a high-resolution mass spectrometer. The masses of the three latter isobars were measured with respect to the abundantly produced¹⁰⁰Ag. The known mass of¹⁰⁰Cd was very well reproduced and the masses of¹⁰⁰In and¹⁰⁰Sn were determined for the first time with precisions of 3×10^?6 and 10^?5, respectively.     

100-Gbit/s bitwise logic

We demonstrate 100-Gbit/s bitwise logic in an all-optical semiconductor optical amplifier-based switching device, the ultrafast nonlinear interferometer. To the best of our knowledge this is the first demonstration of 100-Gbit/s AND and INVERT functionality with a 100-GHz optical clock stream and a 100-Gbit/s data stream as the logical inputs to a semiconductor-based switch. Additionally, 100-Gbit/s inverting and noninverting all-optical wavelength conversion are demonstrated.     

MgO和Si上NbN超薄薄膜的生长研究

我们在单晶MgO(100)、Si(100)和SiOx/Si基片上成功生长了纳米厚度的超薄NbN薄膜,利用现代分析手段:X射线衍射(XRD)、透射电子显微镜(TEM)、原子力显微镜(AFM)等技术分析研究了所制备的超薄NbN薄膜的微观结构、厚度、表面界面情况等物理特性。研究表明,在MgO(100)基片上获得了外延生长的单晶NbN超薄薄膜,在Si(100)和SiOx/Si基片上获得的是多晶NbN超薄薄膜。厚度均约6nm左右。这些超薄薄膜的超导转变温度分别为:MgO上薄膜是14.46K,Si和SiOx上薄膜分别是8.74K和9.01K.     

在Pd/Cu(100)表面上外延的超薄Co膜的结构和磁性

利用脉冲激光溅射(PLD)和分子束外延(MBE)方法制备了超薄膜系统 Co/Pd/Cu(100).脉冲激 光溅射生长的单原子Pd层呈现了很好的二维生长模式.在这个Pd表面上，分子束外延生长的C o层直至12个原子层都表现了层-层生长模式.利用俄歇电子谱(AES)和低能电子衍射(LEED)研 究了该系统的表面结构.利用低温磁光克效应(MOKE)研究了系统的磁学性质.结构研究表明， Co层由于面内晶格失配应力而具有一个四方正交结构；与对比样品Co/Cu(100)的比较研究说 明Pd层的存在强烈地改善了Co膜的起始生长模式和结构.磁光克效应测量表明，Pd层的存在 改变了Co层的磁学性质. 关键词： 薄膜的磁性质 组织与形貌 界面磁性     

A vibrational investigation of the stability, morphology and surface reactivity of NiO on Ni(100)

The formation and thermal stability of NiO on Ni(100) have been investigated using high-resolution electron energy loss spectroscopy (EELS) and low-energy electron diffraction (LEED). Our results indicate that the saturated NiO/Ni(100) layer prepared at 300 K is rather poorly ordered and is thermally unstable at higher temperatures. Heating this NiO/Ni(100) layer to 800 K produces a surface with mixtures of crystalline NiO(100) clusters and c(2 × 2)−O chemisorbed local structures. The long range order of the NiO(100) clusters could be improved by repeated cycles of oxygen adsorption at 300 K followed by heating to 800 K. The NiO(100) clusters obtained after 9 cycles of such dosing-annealing exhibit bulk-like properties, as suggested both by the off-specular EELS measurements and by the experimental observation that the intensities of the multiple loss features follow the expected Poisson distribution. The Ni---O bond strength of the NiO(100) clusters, estimated from the overtone spectra, is 3.6 eV. In addition, the reduction of NiO(100) clusters by H₂ at 800 K has also been investigated. The NiO(100) clusters are reduced preferentially with respect to the c(2 × 2)−O overlayer, resulting in a reduction sequence of NiO(100) → c(2 × 2)−O → p(2 × 2)−O → Ni(100).     

Channeling and axial to planar channeling transition of protons in magnesium oxide

The channeling of 1.7 MeV protons along 〈100〉 axial direction, (100), (110) and (111) planar directions in magnesium oxide single crystals and axial to planar channeling transitions from 〈100〉 to (100), (110) and (210) have been studied experimentally. The experimental data and preliminary analysis of results are presented.     

饱和吸附H原子的Si（100）表面的光学二次谐波研究

测量了Ｓｉ（１００）（２×１）－Ｈ表面和Ｓｉ（１００）（３×１）－Ｈ表面的反射二次谐波强度随温度的变化关系，并与清洁的Ｓｉ（１００）（２×１）表面进行了比较。Ｓｉ（１００）（２×１）表面和Ｓｉ（１００）（３×１）－Ｈ表面的二次谐波强度随温度的上升而单调地减小，Ｓｉ（１００）（２×１）－Ｈ表面二次谐波强度随温度的变化不是单调的，约在４７０Ｋ时信号最大。可以根据二次谐波信号的强度及其随温度的变化关系来确定样品温度和表面结构。     

Cu(100)表面CO分子单层膜的原子结构

利用第一性原理研究了覆盖度分别为1.00, 0.50和0.25 ML时CO分子单层膜在Cu(100)表面的吸附系统. 计算表明CO分子对不稳定. 获得了CO分子单层膜在虚拟Cu(100)表面的原子结构, 以及CO分子单层膜在Cu(100)表面吸附系统的原子结构. 当CO分子单层膜在Cu(100)表面的三个吸附位吸附, 覆盖度为1.00 ML时, 顶位和桥位都稳定, 而空心位不稳定; 覆盖度为0.50和0.25 ML时, 三个吸附位都稳定.比较吸附前后CO分子单层膜的原子结构, 可知CO分子和Cu(100)表面的相互作用强于CO分子单层膜之间的相互作用. 关键词： CO分子单层膜 自组装 CASTEP Cu(100)     

Hydrogen chemisorption on the 100 (2 × 1) surfaces of Si and Ge

This paper combines a theoretical study of the Si(100) surface having a monolayer of atomic hydrogen chemisorbed to it with an experimental study of the analogous Ge(100) and Ge(110) surfaces. In the theoretical work the underlying (100) silicon surface is taken to be reconstructed according to the Schlier-Farnsworth-Levine pairing model with the hydrogen located on the unfilled tetrahedral bonds of this structure. Self-consistent calculations of the electronic potential, charge density, spectrum, and occupied surface density of states are carried out. The force on the hydrogen atoms is then calculated using the Hellman-Feynman theorem. This force is found to be close to zero, confirming that the hydrogen atoms are indeed at the equilibrium position for the chosen silicon geometry. Features in the calculated photoemission spectrum for the Si(100) 2 × 1 : H surface are discussed in terms of related features in the photoemission spectrum of Si(111) : H, but are found not to agree with the previously measured photoemission spectrum of Si(100) 2 × 1 : H. Measured photoemission and ion-neutralization spectra for Ge(100) 2 × 1 : H agree in their major features with what is calculated for Si(100) 2 × 1 : H, however, suggesting that the Ge(100) 2 × 1 : H surface is reconstricted according to the pairing model. Similarly, measured spectra for clean Ge(100) 2 × 1 agree with calculations for the row dimerized Si(100) surface.     

Ultrahigh laser pulse energy and power generation at 10 kHz

This Letter presents results from a new master-oscillator, power-amplifier pulse-burst laser system demonstrating ultrahigh pulse energies greater than 2.0 J/pulse at 1064?nm with interpulse separations of 100?μs (10?kHz) for burst durations of 100 pulses. Each pulse generates peak powers exceeding 130?MW and an average power of approximately 20?kW is generated over a 100-pulse-burst. Pulse energies decrease by less than 10% over a 100 sequential pulses, demonstrating negligible "droop" over long-duration pulse trains. Second-harmonic generation of 532?nm with conversion efficiency greater than 50% is demonstrated for 100-pulse-burst durations.     

Work function measurements by the field emission retarding potential method

Using the field emission retarding potential method true work functions have been measured for the following monocrystalline substrates: W(110), W(111), W(100), Nb(100), Ni(100), Cu(100), Ir(110) and Ir(111). The electron elastic and inelastic reflection coefficients from several of these surfaces have also been examined near zero primary beam energy.     

bcc Fe中刃型位错的结构及能量学研究

基于位错理论，利用分子动力学方法建立了〈100〉{010}，〈100〉{011}，1/2〈111〉{011}和1/2〈111〉{112}刃型位错的芯结构，并计算了这四种刃型位错的形成能、位错芯能量和芯半径.计算结果表明：〈100〉{010}和〈100〉{011}刃型位错的形成能比1/2〈111〉{011}和1/2〈111〉{112}刃型位错的要高，这表明〈100〉刃型位错比1/2〈111〉刃型位错更难形成.而〈100〉{010}和〈100〉{011}刃型位错的芯半径比1/2〈111〉{011}和1/2〈111〉{112}刃型位错的小，这说明在1/2〈111〉刃型位错中位于奇异区的原子数多于〈100〉刃型位错，而这些原子要比完整晶体中的原子具有更大的活性.可见，1/2〈111〉刃型位错比〈100〉刃型位错更易运动，且〈100〉刃型位错在bcc Fe中难以形成. 关键词： bcc Fe 刃型位错 分子动力学模拟     

Thickness-dependent orientation evolution in nickel thin films grown on yttria-stabilized zirconia single crystals

Microstructure evolution along with crystallographic orientation change as a function of film thickness was investigated in Ni thin films grown on (100) yttria-stabilized zirconia (YSZ) single crystal substrates. Texture development with two different orientation relationships, OR1: Ni {111}//YSZ {100} and OR2: Ni {100}//YSZ {100}, cube on cube orientation were identified by X-ray diffraction and transmission electron microscopy depending on the film thickness. The observed orientation transition reveals the existence of a critical thickness (～320?nm) favoring two different orientations in sputtered Ni films on YSZ (100) substrate.     

Surface composition effects on martensitic phase transformations in nickel aluminium nanowires

Atomistic simulations are utilized to quantify the effects of surface composition on stress-induced B2 to body centred tetragonal (BCT) martensitic phase transformations in intermetallic nickel aluminium (NiAl) nanowires. The simulations show that the phase transformation is observed in all considered cases, regardless of the material composition of the transverse {100} surfaces of the initially B2 wires. The results indicate that, for ?100? oriented B2 wires with {100} transverse surfaces, the {100} orientation and not the material composition of the {100} surfaces is the dominant factor in controlling the ability of NiAl alloys to undergo martensitic phase transformations at nanometer scales.     

On the rotation of non-epitaxy crystallites on single crystal substrate

The experimental results of Masson et al. [Surf. Sci. 27 (1971) 463] were further interpreted with regard to the rotation behavior of non-epitaxy Au crystallites on a KCl(100) substrate, which developed into primary epitaxy ([111]_Au 6 [100]_KCl; [11̄0]_Au 6 [010]_KCl), and “second” epitaxy (in fact [100]_Au 6 [100]_KCl; [010]_Au 6 [010]_KCl and [100]_Au 6 [100]_KCl; [010]_Au 6 [011]_KCl) upon annealing at 94°C. These epitaxy orders were clarified to be nonsequential events on the basis of the development of electron diffractions (220), (111) and (200) of Au. The “second” epitaxy can be attributed to the later formation of a (100)_Au|(100)_KCl contact in comparison with the preferred (111)_Au|(100)_KCl contact in the as-deposited state. The Au crystallites with irrational contact plane should have rotated and changed shape before bifurcating into (111)_Au|(100)_KCl and (100)_Au|(100)_KCl contact, upon which viscous rotation was still feasible, until the primary and “second” epitaxy were reached, respectively.     

Decay properties of low-lying levels in100Rh

Zeitschrift für Physik A Hadrons and nuclei - Low-lying levels of100Rh have been investigated with the reaction100Ru(p, nγ)100Rh in the proton energy range 4.4 MeV≦E p≦6 MeV....     

Structure of Epitaxial Layers of KCl on Ag(100)

We investigated the epitaxial growth of thin KCl films on Ag(100) by spot-profile-analysis low energy electron diffraction (SPA-LEED) and scanning tunnelling microscopy (STM). The structural relation of the (100)-oriented KCl film with respect to the Ag(100) surface is incommensurate, nevertheless the structural quality is very high and terraces with an average diameter of 250 Å are obtained. The unit cells of KCl and Ag(100) are aligned, and there is no rotational mosaicity as present in the case of NaCl on Ag(100). We attribute this to a small interaction between KCl and Ag(100) and growth starting at step edges of the metal substrate. In order to demonstrate the high structural quality of the KCl films, we deposited a monolayer of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) on these films. We obtained the identical monolayer structure that was observed earlier on bulk KCl. We thus suggest that KCl/Ag(100) is ideal for surface experiments on thin dielectric films.     

Temperature-pressure-induced solid-solid <100> to <110> reorientation in FCC metallic nanowire: a molecular dynamic study

Atomistic simulation of initial <100> oriented FCC Cu nanowires shows a novel coupled temperature-pressure dependent reorientation from <100> to <110> phase. A temperature-pressure-induced solid-solid <100> to <110> reorientation diagram is generated for Cu nanowire with varying cross-sectional sizes. A critical pressure is reported for Cu nanowires with varying cross-sectional sizes, above which an initial <100> oriented nanowire shows temperature independent reorientation into the <110> phase. The effect of surface stresses on the <100> to <110> reorientation is also studied. The results indicate that above a critical cross-sectional size for a given temperature-pressure, <100> to <110> reorientation is not possible. It is also reported here that for a given applied pressure, an increase in temperature is required for the <100> to <110> reorientation with increasing cross-sectional size of the nanowire. The temperature-pressure-induced solid-solid <100> to <110> reorientation diagram reported in the present paper could further be used as guidelines for controlling the reorientations/shape memory in nano-scale applications of FCC metallic nanowires.