共查询到20条相似文献,搜索用时 156 毫秒
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文章介绍了Z衬度扫描透射电子显微术(Z-scanning transmission electron microscopy,Z-STEM,Z为原子序数)的最新进展:Z-STEM可以直接“观察”到晶体中原子的真实位置,Z衬度图像的分辨率在经过球差校正后可达0.6A;在利用Z衬度成像技术对材料的阴极荧光(cathodoluminescence,CL)性质的研究中,首次观察到了“死层”(dead layer)的存在.然后,文章以半导体与结晶氧化物界面结构、Al72Ni20Co8十角形准晶结构以及SrTiO3晶界结构为例,具体介绍了Z衬度成像在测定物质结构与化学组成方面独特的优势。 相似文献
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实验上探讨了Y3+离子掺杂对La2/3-xYxCa1/3MnO3(0<x<0.2)单相样品的结构及其输运性质的影响.结果表明,随着Y的掺杂,晶胞参数收缩,从顺磁性半导体到铁磁性金属的转变温度Tc明显降低,而巨磁阻效应却大大提高.为了探讨其物理起因,我们对Tc温度以上的导电机理通过定量分析电阻随温度的变化而得以研究,结果表明,载流子的迁移遵从跳跃方式而不是热激活形式,在此基础上对Y掺杂作用进行了讨论. 相似文献
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介绍了2005年国家自然科学奖二等奖获奖项目“微小晶体结构测定的电子晶体学研究”,研究目的是建立一种借助高分辨电子显微像测定晶体结构的新方法.为此提出了高分辨电子显微学与衍射晶体学相结合的思想,在实现此思想的过程中,研究了像衬的规律,得出实用的像衬公式和理论,阐明了不同种类原子像衬与晶体厚度的关系,而且用理论指导实验,观察到晶体中锂原子的像衬,以此理论为依据,把衍射晶体学中的多种分析方法特包是直接法引入到高分辨电子显微学中,建立了一套全新的电子晶体学图像处理技术,开发了相应的可视化专用软件包,并应用于测定多个未知晶体结构.文中逐一介绍了研究工作全过程的关键问题和研究结果。 相似文献
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金刚石半导体由于其特殊的机械性能使其在极端环境下有较广的应用前景. 虽然通过硼(B)元素掺杂较易得到p型金刚石半导体,但具有优异电学性能的n型半导体却鲜见报道. 硼、硫(S)原子因半径及外层电子互补,其协同掺杂易合成p型或n型半导体,但其物理机理尚不清晰.在课题组已有实验报道基础上,借助第一性原理探究了B-S不同比例单掺杂及共掺杂金刚石的形成能、晶体内的存在形式及电子结构,从原子尺度揭示了金刚石由p型向n型半导体转变的阈值掺杂比例. 通过实验与理论的对比发现B在晶格内趋向团聚,而过量的S掺杂则发生析出. 相似文献
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溶胶凝胶合成锰掺杂ZnO的室温磁性行为 总被引:2,自引:0,他引:2
通过溶胶凝胶自燃法合成锰掺杂氧化锌纳米晶体, 研究了Mn掺杂ZnO稀磁半导体(简称DMS)的性质.X射线衍射光谱表明,锰掺杂氧化锌保留纤锌矿型状氧化锌六角晶体结构.采用能量色散X射线能谱和扫描电子显微镜分别对成分和形态进行研究.温度依赖的电阻率显示了DMS的半导体材料行为.振动样品磁强计测定的室温磁性行为,揭示了锰掺杂氧化锌的铁磁性和反磁性特性. 相似文献
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在磁性材料的研究中,磁畴的电镜观测是人们很感兴趣的问题[1]. 利用扫描电镜可以观测到磁性材料的两种磁衬度(图1).第一种磁衬度首先由Joy和Jakubovics利用二次电子信号观测到[3].引起这种磁树度的原因是磁性材料存在着漏磁场.漏磁场引起试样表面发射的二次电子轨道的改变,由于从磁性相反的磁畴中探测到二次电子的效率不同,从而引起磁衬度.由单轴各向异性的磁性材料(如钻和磁泡材料)可得到这种磁衬度[见图1(a)]. 第二种磁衬度首先由Philibert和Tixier[3]利用试样电流得到.以后,更多的研究工作者用背散射电子观测到这种磁树度.这种磁衬度产… 相似文献
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S. Denifl 《The European physical journal. Special topics》2013,222(9):2017-2033
Superfluid helium droplets have provided a new perspective for studying electron induced chemistry at extremely low temperatures. Helium droplets represent an ideal environment for the formation of novel and exotic agglomerates of atoms and molecules. Mass spectrometry can be used to detect the resulting ions formed upon electron ionization and electron attachment to doped droplets. In the case of electron ionization a helium atom of the droplet is ionized initially and after few resonant charge transfer reactions between helium atoms the charge finally localises on the dopant. An alternative process is Penning ionization of the dopant, where the scattered electron first electronically excites a helium atom on the surface of the droplet. The attachment of a low energy electron leads to formation of an electron bubble inside the droplet which decays by autodetachment or localization on a dopant, if present in the droplet. In the present minireview a general overview about the field of electron scattering with doped helium droplets is given and a presentation of important recent results related to these electron collision studies is given as well. 相似文献
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The main components of the SEM are the signal generation and the signal detection and display systems. A finely focussed electron beam scans the specimen surface. Due to the interaction between electrons and solid, signals such as secondary emission, light, X-radiation and currents are generated. Depending on the selected detection system the displayed images provide a variety of information, such as topography, element distribution, surface voltage, luminescence, conductivity, etc. The useful application of the SEM ranges from surface study to bulk analysis to device fabrication. 相似文献
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Franck Bassani Priyanka Periwal Bassem Salem Nicolas Chevalier Denis Mariolle Guillaume Audoit Pascal Gentile Thierry Baron 《固体物理学:研究快报》2014,8(4):312-316
Silicon nanowires (SiNWs) with axial doping junctions were synthesized via the Au‐catalyzed vapor–liquid–solid growth method with the use of HCl. In this work, dopant profiling from three axially doped SiNWs with p–i, p–n and n–i–p junctions were investigated using both scanning electron microscopy (SEM) and scanning capacitance microscopy (SCM). It turns out that observed doping contrasts in SEM are also affected by the surface roughness and sample charging. In contrast, SCM allows us to delineate with sub‐10 nm resolution the electrical junctions and provides a relative value of the doping concentration in each segment of the NW. SCM clearly evidences the expected doping regions within these SiNWs thanks to the addition of HCl during the growth that strongly prevents shell overgrowth. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Shao-Ju Shih Ying-Ying Wu Konstantin B. Borisenko 《Journal of nanoparticle research》2011,13(12):7021-7028
The morphology and distribution of dopant in yttrium-doped ceria (YDC) nanoparticles prepared by spray pyrolysis were characterised
by transmission electron microscopy and X-ray energy dispersive spectroscopy (XEDS), respectively. By combining the XEDS analysis
and concentration distribution modelling, accurate yttrium dopant concentration variation from the particle center to the
surface can be determined. It is shown that by appropriately selecting cerium precursors, the yttrium dopant distribution
in YDC nanoparticles can be controlled. Uniform yttrium distribution in the YDC particles has been achieved, which is important
to decrease probability of yttrium cluster segregation to improve oxygen ion conductivity in solid oxide fuel cell electrolytes.
This control is based on the suggested mechanism of dopant distribution which proposes that hydration energies influence diffusion
rates of the precursors during preparation process. In addition, the morphology (solid spherical, hollow spherical and hollow
concave) formation mechanisms of the YDC particles from different cerium precursors are discussed. 相似文献
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Matthew J. Smith Meng-Ju Sher Benjamin Franta Yu-Ting Lin Eric Mazur Silvija Gradečak 《Applied Physics A: Materials Science & Processing》2014,114(4):1009-1016
We study the dopant incorporation processes during thin-film fs-laser doping of Si and tailor the dopant distribution through optimization of the fs-laser irradiation conditions. Scanning electron microscopy, transmission electron microscopy, and profilometry are used to study the interrelated dopant incorporation and surface texturing mechanisms during fs-laser irradiation of Si coated with a Se thin-film dopant precursor. We show that the crystallization of Se-doped Si and micrometer-scale surface texturing are closely coupled and produce a doped surface that is not conducive to device fabrication. Next, we use this understanding of the dopant incorporation process to decouple dopant crystallization from surface texturing by tailoring the irradiation conditions. A low-fluence regime is identified in which a continuous surface layer of doped crystalline material forms in parallel with laser-induced periodic surface structures over many laser pulses. This investigation demonstrates the ability to tailor the dopant distribution through a systematic investigation of the relationship between fs-laser irradiation conditions, microstructure, and dopant distribution. 相似文献
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Andrew A. Cederberg 《Surface science》1981,103(1):148-176
Inelastic election tunneling spectroscopy (IETS) is a sensitive technique for obtaining vibrational spectra of molecules adsorbed on an oxide surface and incorporated into a metal-oxide-metal tunnel junction. IETS energy data are used routinely. However, IETS intensities contain additional information which, for theoretical and experimental reasons, has not been used systematically. This paper examines the variation of IETS intensity with surface coverage of dopant molecules in the junction, a relationship of practical and theoretical importance. IET spectra are taken using standard experimental techniques and a liquid doping technique which allows the surface coverage to be determined independently. From an analysis of a large number of modes of benzoic acid on alumina, it is found that IETS intensity, defined in the usual way as the normalized change in conductance, , is a nonlinear function of surface coverage. A physical model is presented which attributes this behavior to a difference in elastic tunneling conductances through empty or filled regions of the dopant layer in a junction with a fraction of a monolayer coverage. In addition, the liquid and vapor doping techniques in common use in IETS are discussed in terms of statistical mechanics and are shown to be manifestations of the same basic phenomenon. 相似文献
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Confocal laser scanning microscopy and scanning electron microscopy of tissue Ti-implant interfaces.
Microscopic inspection of heterogenous three-dimensional (3D) objects such as oral implants, or implants in general, is conventionally performed either on ground sections of methyl-metacrylate-embedded material, at the cellular level by histologic analysis of the peri-implant tissue by light microscopy (LM), or at the supramolecular level by transmission electron microscopy (TEM). Alternatively, the architecture of the tissue/implant interface is visualized by scanning electron microscopy (SEM). The two approaches exclude each other because of the sample preparation.We elaborate conditions for the non-invasive analysis of tissue/implant interfaces by confocal laser scanning microscopy (CLSM) in buffer, hoping to obtain a 3D view of fluorescently labeled tissue constituents at the tissue implant interface and, through subsequent SEM, of the metal surface. The use of water-immersion objectives, originally developed for high LM under physiological conditions is essential.In an exploratory approach, the tissue/Ti-interfaces of two retrieved dental implants were analyzed. One was a step-cylinder used for orthodontic anchoring and the other was an endosseous step-screw implant retrieved after infection-related loosening prior to load. The adhering tissue fragments were fluorescently triple-labeled for actin, fibronectin, and sm-alpha-actin. Optical sections for fluorescent images and for the laser reflection map were registered concomitantly. This approach allowed the labeled structures to be located on the metal surface. Subsequently, the same implants were prepared for SEM of the tissue/implant interface, and upon removal of the adhering structures, of the underlying metal surface. Thus, specific proteins can be identified and their spatial architecture as well as that of the underlying metal surface can be visualized for one and the same implant. The immediate visualization after fluorescence labeling in buffer by means of water immersion objective lenses proved most critical. 相似文献
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A scanning electron microscope (SEM) is employed to investigate the temperature effect on the charging behaviour of alkali-silicate glasses under electron beam irradiation using electrostatic influence method (EIM). A modified special arrangement adapted to the SEM allows to study charging mechanisms and charge transport characteristics of these glasses using the simultaneous measurement of displacement and leakage currents. The trapping process during continuous electron irradiation can be directly determined by the EIM. The experimental results reveal that the charging ability of glasses decreases with increasing temperature. The variation of charge process has been confirmed by measuring the surface potential in response to the sample temperature. In this report, we introduce also the secondary electron emission (SEE) yield. It was found the strong dependence of the SEE yield on the temperature variation. The higher is the temperature and the lower is the SEE yield. The trapping ability is analyzed taking into account the regulation mechanisms involved under electron irradiation. 相似文献
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Secondary ion mass spectrometry (SIMS) is frequently used as the preferred tool for dopant profiling due to its sensitivity and depth resolution. However, as dopant profiles become shallower most, if not all of the implant profile lies in the pre-equilibrium or transient region of an SIMS depth profile. In this region sputter yield and ionisation rate vary making accurate quantification of the implant profile very difficult. These problems can be reduced through the use of much lower beam energies or oxygen flooding of the sample. However, most SIMS instruments do not have these capabilities. In this paper an alternative technique for producing an accurate depth profile of a shallow implant, using existing SIMS technology is presented.Through the fabrication of bevels with very small slope angles on a shallow boron implanted silicon via a chemical etch, SIMS ion imaging is performed on the exposed surface. Ion image data is then summed, and in conjunction with accurate measurement of the bevel morphology, a shallow boron implant profile produced. The ‘bevel-image’ profile compares very well with a profile obtained using a 1 keV oxygen beam. To ensure a good dynamic range on the ‘bevel-image’ profile it is important to clean the bevel with a HF etch, prior to imaging. 相似文献
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Ph. Ebert 《Applied Physics A: Materials Science & Processing》2002,75(1):101-112
This work reports the measurement of the nano-scale physical properties of surface vacancies and the extraction of the types
and concentrations of dopant atoms and point defects inside compound semiconductors, primarily by cross-sectional scanning
tunneling microscopy on cleavage surfaces of III–V semiconductors. The results provide the basis to determine the physical
mechanisms governing the interactions, the formation, the electronic properties, and the compensation effects of surface as
well as bulk point defects and dopant atoms.
Received: 10 May 2001 / Accepted: 23 July 2001 / Published online: 3 April 2002 相似文献