共查询到20条相似文献,搜索用时 46 毫秒
1.
Room-temperature attenuation measurements are made between lambda=0.8 and 10.0 microm on three GaAs epitaxial samples containing layers of ErAs nanoparticles. An asymmetric attenuation peak is observed around 2.5 microm that increases in strength with ErAs density, and is modeled well by a Maxwell-Garnett formulation and semiclassical transport theory. The nanoparticles are assigned a distribution function of oblate spheroids having a minimum volume corresponding to a 1.0-nm sphere. This is consistent with the self-organizing tendency of ErAs in GaAs, and explains the sharp attenuation peak as a spherical-particle surface-plasmon (i.e., Fr?hlich) resonance. 相似文献
2.
Ville Arpiainen 《Surface science》2005,584(1):27-34
The electronic structure of GaAs(1 1 0) surface is analyzed using Density Functional Theory (DFT-GGA) in atomic orbital basis (LCAO). The surface orbitals and the corresponding local density of electronic states (LDOS) are calculated for purposes of interpreting STM images. We show how local atomic orbitals of surface atoms are related to tunneling channels for electrons in STM imaging. A destructive interference between orbitals of two neighbouring atoms increases the contrast between the two atoms, and this is reflected in directionality of STM patterns of GaAs(1 1 0) surfaces. We also discuss how the basic formalism of Tersoff-Hamann approach to STM simulation can be reformulated to reveal the role of phase difference between tunneling channels. 相似文献
3.
Masahiko Nishida 《Surface science》1981,109(3):557-566
The interface states of Ge-GaAs(111) and () heterojunctions are calculated by applying extended Hückel theory to a superlattice with alternating Ge and GaAs atomic layers. The band-edge discontinuity, interface bands, and local densities of states are presented. It is found that no interface states are revealed in the fundamental gaps of Ge and GaAs and that there is an appreciable difference in electronic structure between both kinds of interface. 相似文献
4.
《Superlattices and Microstructures》1996,20(1):117-123
The atomic and electronic structures of semiconductor heterostructures are investigated by using the tight-binding (TB) electronic theory, taking into account the realistic atomic irregularities, such as steps and misfit dislocations at the interface. Particular attention has been paid to the 1/2〈110〉(001) misfit dislocation of the wide gap II-VI semiconductor heterostructures, like ZnSe/GaAs(001) systems. It is shown that steps at the interface do not produce deep gap states, but they influence significantly the deep states associated with the misfit dislocations. The stability and degradation of II-VI semiconductor heterostructures are discussed in terms of the introduction of the misfit dislocations. 相似文献
5.
A. Dorn M. Peter S. Kicin T. Ihn K. Ensslin D. Driscoll A. C. Gossard 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):426
Self-assembled ErAs islands were grown on GaAs between a two-dimensional electron gas (2DEG) and a backgate electrode by molecular-beam epitaxy. The islands have overlapping Schottky barriers that form an insulating potential barrier. A TiAu topgate was added by shadow mask evaporation. Thermal activation and charging experiments were employed to gain insight into the electronic properties of the ErAs island systems. In addition the 2DEG was characterized as a function of topgate and backgate voltage. 相似文献
6.
We present the spin and orbitally resolved local density of states (LDOS) for a single Mn impurity and for two nearby Mn impurities in GaAs. The GaAs host is described by a sp(3) tight-binding Hamiltonian, and the Mn impurity is described by a local p-d hybridization and on-site potential. Local spin-polarized resonances within the valence bands significantly enhance the LDOS near the band edge. For two nearby parallel Mn moments the acceptor states hybridize and split in energy. Thus scanning tunneling spectroscopy can directly measure the Mn-Mn interaction as a function of distance. 相似文献
7.
Klaus Halterman Oriol T. Valls 《Physica C: Superconductivity and its Applications》2005,420(3-4):111-124
We analyze the local density of states (LDOS) of heterostructures consisting of alternating ferromagnet, F, and superconductor, S, layers. We consider structures of the SFS and SFSFSFS type, with thin nanometer scale F and S layers, within the ballistic regime. The spin-splitting effects of the ferromagnet and the mutual coupling between the S regions, yield several nontrivial stable and metastable pair amplitude configurations, and we find that the details of the spatial behavior of the pair amplitude govern the calculated electronic spectra. These are reflected in discernible signatures of the LDOS. The roles that the magnetic exchange energy, interface scattering strength, and the Fermi wavevector mismatch each have on the LDOS for the different allowed junction configurations, are systematically investigated. 相似文献
8.
The local density of states (LDOS) at the epitaxially grown InAs surface on a GaAs(111) A substrate were characterized using low-temperature scanning tunneling microscopy. Using dI/dV signal mapping, LDOS standing waves were clearly imaged at point defects and within nanostructures. Measurement of the wavelength as a function of bias voltage showed a nonparabolic dispersion relation for the conduction band. The observed wave features originate from the Friedel oscillations of the two-dimensional electron gas in the semiconductor surface accumulation layer. 相似文献
9.
Chanchal Ghosh 《Journal of Physics and Chemistry of Solids》2009,70(6):1024-1029
Results of theoretical investigation on the structural and electronic properties of GaAs/AlAs and AlAs/GaAs core/shell nanoparticles are presented. We have considered relaxed structures of essentially spherical parts of the zinc-blende crystal structure. The electronic properties and the total energy were calculated using density-functional tight-binding method. Our results include the charge distribution, density of states (DOSs), electronic energy levels (in particular HOMO and LUMO), HOMO-LUMO gap, excitation spectra and their variation with shell thickness for both GaAs/AlAs and AlAs/GaAs core/shell systems. 相似文献
10.
Ultrafast optical switching of terahertz metamaterials fabricated on ErAs/GaAs nanoisland superlattices 总被引:1,自引:0,他引:1
Chen HT Padilla WJ Zide JM Bank SR Gossard AC Taylor AJ Averitt RD 《Optics letters》2007,32(12):1620-1622
We demonstrate optical switching of electrically resonant terahertz planar metamaterials fabricated on ErAs/GaAs nanoisland superlattice substrates. Photoexcited charge carriers in the superlattice shunt the capacitive regions of the constituent elements, thereby modulating the resonant response of the metamaterials. A switching recovery time of 20 ps results from fast carrier recombination in the ErAs/GaAs superlattice substrates. 相似文献
11.
Suzuki K Kanisawa K Janer C Perraud S Takashina K Fujisawa T Hirayama Y 《Physical review letters》2007,98(13):136802
We measure the spatial distribution of the local density of states (LDOS) at cleaved surfaces of InAs/GaSb isolated quantum wells and double quantum wells (DQWs) by low-temperature scanning tunneling spectroscopy. Distinct standing wave patterns of LDOS corresponding to subbands are observed. These LDOS patterns and subband energies agree remarkably well with simple calculations with tip-induced band bending. Furthermore, for the DQWs, coupling of electronic states between the quantum wells is also clearly observed. 相似文献
12.
The electronic properties of the interface of Fe/GaAs(001) have been investigated by using first-principles and molecular-dynamics techniques. While the ground state is ferromagnetic for all structures considered, a ferrimagnetic spin structure is found to be very close in energy (<1 meV). The observed lowering of the magnetic moments when relaxing the atomic positions is believed to be connected to this close in energy lying metamagnetic state. On the other hand, the magnetic moments of the Fe atoms at the interface are large, which can be explained by the bulk-like behavior of the density ot states of interface atoms. 相似文献
13.
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
14.
15.
16.
We have implemented first-principles relativistic pseudopotential calculations within general gradient approximation to investigate the structural and electronic properties of quaternary InAs/GaSb superlattices with an InSb or GaAs type of interface. Because of the complexity and low symmetry of the quaternary interfaces, the interface energy and strain in the InAs/GaSb superlattice system have been calculated to determine the equilibrium interface structural parameters. The band structures of InAs/GaSb superlattices with InSb and GaAs interfaces have been calculated with respect to the lattice constant and atomic position relaxations of the superlattice interfaces. The calculation of the relativistic Hartree–Fock pseudopotential in local density approximation has also been performed to verify the calculated band structure results that have been predicted in other empirical theories. The calculated band structures of InAs/GaSb superlattices with different types of interface (InSb or GaAs) have been systematically compared. We find that the virtual–crystal approximation fails to properly describe the quaternary InAs/GaSb superlattice system, and the chemical bonding and ionicity of anion atoms are essential in determining the interface and electronic structures of InAs/GaSb superlattice system. 相似文献
17.
《Physica E: Low-dimensional Systems and Nanostructures》2011,43(10):2841-2845
An attempt to control surface electronics of III–V semiconductor using wet chemical processes has been performed. Here, we report results on the use of self-assembled monolayers (SAMs) of organic molecules on (0 0 1) GaAs surface. Octadecanethiol (ODT) and benzenethiol (BT) have been the choice in the present study.GaAs wafers were modified by thiol molecules on the flat surface after the native oxide layers are removed by chemical etching under optimized conditions. The change in the electronic properties was measured in terms of transport properties via the SAM layer by conductive probe atomic force microscopy. The current–voltage characteristics thus obtained show that ODT functions as a tunnel barrier while BT is conductive due to the presence of π-electrons. As a result, we can control the electronic states of GaAs–molecule interface for realizing novel device structures by the selection of functional molecules. 相似文献
18.
Summary This work reports the electronic structure of GaInAsSb quaternary alloy by recursion method. A five-orbital sp3s* per atom model was used in the tight-binding representation of the Hamiltonian. The local density of states (LDOS), integrated
density of states (IDOS) and structural energy (ST.E) were calculated for Ga, In, As and Sb sites in Ga0.5 In0.5 As0.5 Sb0.5 and GaInAsSb lattice matched to GaAs and the same alloy lattice matched to GaSb. There are 216 atoms in our cluster arranged
in a zincblend structure. The results are in good agreement with available information about the alloy. 相似文献
19.
The formation of the interface between the GaAs(100) single-crystal surface and PTCDA and NTCDA organic semiconductors is
investigated. The method of total current spectroscopy makes it possible to trace the formation of the interfacial electronic
structure. The two organic materials and the GaAs substrate are bonded together when the π electron cloud of an aromatic ring
spreads toward the substrate. This modifies the electronic states of interfacial organic molecules and generates a dipole
at the interface. 相似文献
20.
通过广义梯度近似的第一原理全电子相对论计算, 研究了不同界面类型InAs/GaSb超晶格的界面结构、电子和光吸收特性. 由于四原子界面的复杂性和低对称性, 通过对InAs/GaSb超晶格进行电子总能量和应力最小化来确定弛豫界面的结构参数. 计算了InSb, GaAs型界面和非特殊界面(二者交替)超晶格的能带结构和光吸收谱, 考察了超晶格界面层原子发生弛豫的影响.为了证实能带结构的计算结果, 用局域密度近似和Hartree-Fock泛函的平面波方法进行了计算. 对不同界面类型InAs/GaSb超晶格的能带结构计算结果进行了比较, 发现界面Sb原子的化学键和离子性对InAs/GaSb超晶格的界面结构、 能带结构和光学特性起着至关重要的作用. 相似文献