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1.
Kinetics in surface reconstructions on GaAs(001) 总被引:1,自引:0,他引:1
We have successfully controlled the surface structures of GaAs(001) by changing incident As-molecular species. Under As4 fluxes, the c(4 x 4) reconstruction with Ga-As dimers [c(4 x 4)alpha structure] is obtained, but the formation of three As-As dimer structures [c(4 x 4)beta structure] is kinetically limited. On the other hand, the structure change from the (2 x 4), through c(4 x 4)alpha, to c(4 x 4)beta phases is observed under As2 fluxes. We found that the c(4 x 4)alpha structure is energetically metastable and provides a kinetic pathway for the structure change between the (2 x 4) and c(4 x 4)beta phases under As2 fluxes. 相似文献
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During epitaxial growth of MnAs on GaAs(001) by molecular-beam epitaxy (MBE) the surface exhibits various reconstructions depending on the growth conditions. These reconstructions have been studied during growth by reflection high-energy electron diffraction (RHEED) and reflectance difference spectroscopy (RDS). A feature sensitive to the surface structure was identified in the RD spectra. After growth, the (1×2) and (1×1) reconstructions were cooled down to room temperature and imaged in ultrahigh vacuum with a conventional scanning tunneling microscope (STM). Atomic-scale images of these surfaces are presented. 相似文献
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In experiments on the adsorption and thermal desorption of Cs on GaAs(001) surfaces with various atomic reconstructions and
compositions including those enriched in the cation (gallium) and in the anions (arsenic and antimony), the correlation in
the behavior of the atomic structure and the surface electronic states, which determine the band bending, has been established.
The cesium adsorption on the anion-rich surfaces results in both the similar disordering of the atomic structure and in the
close dose dependences of the band bending, while the adsorption on the Ga-rich surface is ordered and results in the qualitatively
different dose dependence, which has several maxima and minima. In the Cs desorption and the subsequent adsorption-desorption
cycles, the stabilizing effect of Sb on the atomic structure and the electronic states of the Cs/Sb/GaAs(001) surface has
been revealed. 相似文献
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X. Ding Kh. Moumanis J.J. Dubowski E.H. Frost E. Escher 《Applied Physics A: Materials Science & Processing》2006,83(3):357-360
To reliably immobilize different biomoieties on surfaces of III-V semiconductors is one of the most critical issues in the
development of biodetector devices based on the optical/electronic properties of these materials. Herein we demonstrate the
successful immobilization of avidin, a robust and well-studied protein, on a (001) GaAs surface. The immobilization was investigated
via specific binding to biotin, which was connected to the GaAs surface through commercially available long- or short-chain
amino group terminated alkanethiols (HS(CH2)11NH2 or HS(CH2)2NH2), or through a biotinylated thiol synthesized in our laboratory. The immobilization performance was evaluated by photoluminescence
and fluorescence microscopy measurements. We found that the biotinylated thiol mixed with a diluent thiol provides the highest
avidin immobilization efficiency.
PACS 81.05.Ea; 82.65.+r; 87.14.Ee 相似文献
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Using the pseudopotential method and the local density approximation of density functional theory we have investigated the stability, atomic geometry, and electronic states for low-coverage Ca adsorbates on the Si(001) surface within the (2 × n) reconstructions with n = 2, 3, 4, 5. Our total energy calculations suggest that the (2 × 4) phase represents the most energetically stable structure with the Ca coverage of 0.375 ML. Within this structural model, each Ca atom is found to form a bridge with the inner two Si–Si dimers. The inner Si–Si dimers become elongated and symmetric (untilted). The band structure calculation indicates that the system is semiconducting with a small band gap. Significant amount of charge transfer from the Ca atoms to neighbouring Si atoms has been concluded by analysing the electronic charge density and simulation of scanning tunnelling microscopy images. The highest occupied and lowest unoccupied electronic states are found to arise from the inner and outer Si–Si dimer components, respectively. 相似文献
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The surface structure of the As-stabilized GaAs(001)-c(4 x 4) surface has been studied. We show that the seemingly established three As-dimer model is incompatible with experimental data and propose here a new structure model which has three Ga-As dimers per c(4 x 4) unit cell. This mixed dimer model, confirmed by the rocking-curve analysis of reflection high-energy electron diffraction and first-principles calculations, resolves disagreements in the interpretation of several previous experiments. A good agreement between the observed scanning tunneling microscopy image and the simulated one further confirms the newly proposed model. 相似文献
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The (111)B surface of GaAs has been investigated using scanning tunneling microscopy (STM) and a number of different reconstructions have been found at different surface stoichiometries. In accordance with electron diffraction studies, we find the series (2 × 2), (1 × 1)LT, (
) and (1 × 1)HT with increasing annealing temperature, corresponding to decreasing surface As concentration. The (1 × 1)LT is of particular interest, since it only occurs in a narrow temperature window between the two more established reconstructions, the (2 × 2) and the (
). We find the (1 × 1)LT to take the form of a mixture of the local structures of both the (2 × 2) and (
) phases, rather than having a distinct structure. This is behaviour consistent with a kinetically limited system, dominated by the supply of As adatoms to the surface, and may be an example of a continuous phase transition. Above the (1 × 1)LT transition, atomic resolution images of the (
) surface reveal only a three-fold symmetry of the hexagonal structural units, brought about by inequivalent surface bonding due to the 23.4° rotation of the surface unit cell relative to the substrate. This is responsible for the disorder found in the (
) reconstruction, since the structure may form in one of two domains. At lower surface As concentration, the (1 × 1)HT surface adopts a structure combining small domains of a
19.1° structure and random disorder. There is no apparent similarity between the (1 × 1)LT and (1 × 1)HT structures, which may be due to our measurements being conducted at room temperature and without an As flux to control the surface As concentration. 相似文献
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通过第一性原理计算,系统地研究了Mn/GaAs(001)表面的各种再构和相应的局域电子态密度分布,以及表面上Mn的磁矩与各种再构间的对应关系.结果发现,Mn的行为类似电荷施主,将向GaAs表面提供电子,数量依表面的需求而定;直接与Mn的磁矩相联系的d轨道,既可以向GaAs表面施予电子,以弥补Mn的s电子的不足,又可以吸纳因GaAs表面饱和而富余的s电子.这些概念可有效地简化对金属引起的半导体表面再构的理论描述.
关键词:
表面再构
Mn/GaAs(001)
第一性原理计算 相似文献
13.
Shibin Li Jiang Wu Zhiming Wang Zhenhua Li Yuanjie Su Zhiming Wu Yadong Jiang Gregory J. Salamo 《固体物理学:研究快报》2012,6(1):25-27
When a GaAs(001) substrate is heated up to 650 °C in a scanning electron microscope (SEM) vacuum chamber with vacuum range from 10–4 Torr to 10–5 Torr, real‐time SEM observation reveals microscale pits on GaAs substrate surface. The annealing process of GaAs substrate in vacuum causes excess evaporation of arsenic and accumulation of gallium as liquid droplets on the surface. As the function of electrochemical drills, the gallium droplets etch away GaAs beneath the surface to make microscale holes on GaAs substrate. With small amount of oxygen in the chamber acting as etching catalyst, gallium droplets etch GaAs much faster than in ultra‐high vacuum (UHV) MBE chamber. This process provides an easy technique to fabricate microscale pits on GaAs(001) surface.
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We demonstrate fourth-harmonic generation from a GaAs(001) surface by using femtosecond pulses well below damage threshold. Our data reveal a strong fourfold anisotropic surface-specific polarization that is not present in second-harmonic generation and is nearly as strong as the bulk polarization. 相似文献
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S. E. Kulkova S. V. Eremeev A. V. Postnikov D. I. Bazhanov B. V. Potapkin 《Russian Physics Journal》2006,49(10):1088-1096
The atomic and electronic structures of α, β, β2, and ζ reconstructions for the Ga-terminated GaAs (001)-(4×2) surface are investigated in the framework of the pseudopotential approach. Total, surface, and local densities
of electron states, electron-energy spectra, and relative surface energies of the structures under consideration are calculated.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 44–52, October, 2006. 相似文献
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The adsorption of Li and K atoms on the (001) surface of tungsten is found to exhibit remarkable differences in the surface core-level shifts (SCLS) of the W 4f level and in adsorbate-induced changes of the transition temperature of the substrate surface reconstruction. Density-functional theory calculations suggest that these results reflect mainly the different bonding geometry of the adatoms, and, for example, the adsorption of potassium is largely affected by an adsorbate-induced reconstruction of the substrate (dimerization of W atoms). 相似文献
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W.G. Schmidt 《Applied Physics A: Materials Science & Processing》1997,65(6):581-586
Received: 21 March 1997/Accepted: 12 August 1997 相似文献
20.
The microscopic nature of the selective interaction of iodine with an As- and Ga-stabilized GaAs(001) surface has been investigated
by the photoelectron emission and ab initio calculations. The adsorption of iodine on the Ga-stabilized (4 × 2)/c(8 × 2) surface leads to the formation of the prevailing chemical bond with gallium atoms; to a significant redistribution
of the electron density between the surface Ga and As atoms; and, as a result, to a decrease in their binding energy. Iodine
on the As-stabilized (2 × 4)/c(2 × 8) surface forms a bond predominantly with surface arsenic atoms. Such a selective interaction of iodine with the reconstructed
surfaces gives rise to the etching of the Ga-stabilized surface and the passivation of the As-stabilized surface; this explains
the layer-by-layer (“digital”) etching of GaAs(001) controlled by the reconstruction transitions on this surface. 相似文献