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利用x射线光电子衍射的极角扫描模式,采集了GaN(0001)表面由(1010)和(1120)晶面产生的光电子衍射实验曲线,并运用光电子衍射的前向聚焦效应确定了GaN(0001)表面是Ga在最外层的极性面.利用与能量有关的光电子衍射即角分辨光电发射精细结构谱技术并结合多重散射团簇模型计算对GaN(0001)表面的极化性质进行了研究,进一步证实了GaN表面是Ga在最外层的极性面.
关键词:
GaN
表面极性
光电子衍射 相似文献
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DDP表面修饰PbS纳米微粒的合成及结构表征 总被引:2,自引:0,他引:2
采用表面修饰法合成了二烷基二硫代磷酸修饰的PbS纳米微粒,并用红外光谱,(IR),X射线衍射(XRD),透射电子显微镜(TEM),X射线光电子能谱(XPS)等仪器表征了其结构。结果表明,所合成的PbS纳米微粒是DDP表面修饰层和PbS纳米核所构成的,且由于表面修饰层的存在,有效地阻止了纳米微粒在空气中的团聚及氧化,其平均粒径为7nm。 相似文献
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本文综述了应用同步辐射光源的几种主要表面物理研究技术。内容包括:同步辐射光电子能谱(SRPES)、表面广延X射线吸收边精细结构(SEXAFS)、光电子衍射(PED)和掠角入射X射线衍射(GIXD)等。对每种技术的原理、应用实例和最新进展都作了较详细的介绍。 相似文献
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光电子全息的计算机模拟和数值重视 总被引:1,自引:0,他引:1
X射线被原子的芯能级吸收后,激发产生的光电子波在传播过程中被周围的原子散射,同源产生的带有周围原子结构信息的散射波(物波)与未被散射的光电子波参考波),具有良好的相干性,这两列波的衍射图即是光电子全息图。通过重现全息图,可重构三维空间原子像,获得原子级分辨率的三维结构信息。采用合理的物理模型,对c(2×2)S/Ni表面中S原子,金属Cu原子以及YBCO原胞中的Cu2原这邻的一些原子簇,进行了光电子 相似文献
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角分辨光电子能谱技术及其应用进展 总被引:3,自引:0,他引:3
角分辨光电子能谱(ARPES)是研究晶体表面电子结构,如能带,费米面,以及多体相互作用的重要工具。本文概述了光电子激发的一般过程和单粒子近似下的理论模型。详细讨论了角分辨光电子能谱的能带勾画(Energy Band Mapping)和费米面成像(Fermi Surface Mapping)技术,以及高分辨下的角分辨光电子能谱在强相关体系研究中的应用。文章最后简单介绍了当前角分辨光电子能谱研究的新进展,如研究宽禁带半导体材料的表面电子结构,有机功能材料与金属的界面,金属超薄膜中的量子阱态,以及高温超导机理研究等。 相似文献
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六十年代末,由于超高真空条件的获得,使低能电子衍射仪(LEED)逐渐发展成为实用的表面结构分析手段[1].在理论上,几种LEED的动力学理论也相继出现[2-4].利用LEED实验与理论计算的比较,可以决定长程有序表面结构,但对无序表面结构测定,LEED则无能为力. 七十年代中期开始,人们着手寻找一种新的表面结构分析方法,这种方法以LEED为基础,又弥补了它的不足.LEED的入射电子源是非相干源,如果用单色光激发表面层内原子,使之发射光电子,则这种光电子是相干电子源.光电子在固体中的衍射过程与LEED一样,分析光电子的衍射谱而获得表面原子结… 相似文献
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A diffraction theory of continuous-wave photothermal deflection (PD) spectroscopy with fundamental and harmonic responses is presented. The displacement of the probe beam centroid is found to be a rigorous measurement of PD effect, which leads to a set of analytical solutions to the fundamental and the second-order harmonics. Harmonics are caused by the diffraction of the probe beam in the mirage region, which could not be handled by geometric-optics theory. This theory can be used to study bulk materials, thin films, and layered-structure samples. Experimental results are in good agreement with the theory. 相似文献
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《Surface science》1994,302(3):L336-L341
The linear superposition approximation proposed by Wander, Pendry and Van Hove for efficient low-energy electron diffraction calculations (“linear LEED”) is applied to photoelectron diffraction (“linear PD”). As with linear LEED, linear PD works very well for calculating the effect of displaced atoms. However, due to strong forward scattering at higher energies, linear PD requires that atoms do not move into or out of alignment. This limitation can be removed by suitable simple adjustments to the basic approximation, promising to make the method effective for structural searches of complex surfaces. 相似文献
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用无衍射光子束写入细微图形的CAM技术 总被引:1,自引:1,他引:0
本文提出了用无衍射光子束写入细微图形的新方法,从理论上论证了无衍射光子束的生成机理.设计了无衍射光子束的发生装置.介绍了已研制成功的CAM光刻机. 相似文献
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A. A. Dyshekov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(6):956-964
A new version of the X-ray diffraction dynamical th eory in perfect crystals is presented. The theory is based on direct analysis
of Maxwell equations taking into account the model approximations of the character of X-ray-crystal interaction corresponding
to the Evald—Laue theory. The method modification of many scales is used as a mathematical method for approximate solution
of the diffraction equation. The obtained results correspond to the known conclusions of the diffraction dynamical theory
beyond the area of full external reflection. The expressions for the reflection amplitude factors of diffracted and specular
waves for arbitrary angles including the area of full external reflection have been obtained. 相似文献
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Rusz J Cmejla R Ruzickova H Ruzicka E 《The Journal of the Acoustical Society of America》2011,129(1):350-367
An assessment of vocal impairment is presented for separating healthy people from persons with early untreated Parkinson's disease (PD). This study's main purpose was to (a) determine whether voice and speech disorder are present from early stages of PD before starting dopaminergic pharmacotherapy, (b) ascertain the specific characteristics of the PD-related vocal impairment, (c) identify PD-related acoustic signatures for the major part of traditional clinically used measurement methods with respect to their automatic assessment, and (d) design new automatic measurement methods of articulation. The varied speech data were collected from 46 Czech native speakers, 23 with PD. Subsequently, 19 representative measurements were pre-selected, and Wald sequential analysis was then applied to assess the efficiency of each measure and the extent of vocal impairment of each subject. It was found that measurement of the fundamental frequency variations applied to two selected tasks was the best method for separating healthy from PD subjects. On the basis of objective acoustic measures, statistical decision-making theory, and validation from practicing speech therapists, it has been demonstrated that 78% of early untreated PD subjects indicate some form of vocal impairment. The speech defects thus uncovered differ individually in various characteristics including phonation, articulation, and prosody. 相似文献
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FRTH(fractional Fourier transform hologram) is a new kind of hologram that differs from common Fresnel holograms and Fourier transform holograms. Due to the flexibility of zone plate. A method that uses the -1 order diffraction wave of zone plate as the object wave and the 0 order diffraction wave as the reference wave to record FRTH is presented. It provides a new simple way to record FRTH. In this paper, the theory of achieving FRT and recording FRTH using holographic zone plate is presented and experimental results are given. 相似文献
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Krüger P Bourgeois S Domenichini B Magnan H Chandesris D Le Fèvre P Flank AM Jupille J Floreano L Cossaro A Verdini A Morgante A 《Physical review letters》2008,100(5):055501
The charge distribution of the defect states at the reduced TiO(2)(110) surface is studied via a new method, the resonant photoelectron diffraction. The diffraction pattern from the defect state, excited at the Ti-2p-3d resonance, is analyzed in the forward scattering approach and on the basis of multiple scattering calculations. The defect charge is found to be shared by several surface and subsurface Ti sites with the dominant contribution on a specific subsurface site in agreement with density functional theory calculations. 相似文献
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1 Introduction FRT(FractionalFourierTransform )wasfirstlyintroducedbyNamiasin 1 980asamathematictoolinquantummechanics[1] .In1 993,MendlovicandOzaktasimplementedtheFRTatopticalfieldwhentheystudiedgradientindex (GRIN )fiber[2 ] andappliedthepuremathematicformulatio… 相似文献