A UNION OF THE REAL-SPACE AND RECIPROCAL-SPACE VIEW OF THE GaAs(001) SURFACE (original) (raw)
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New Ga-enriched reconstructions on the GaAs(001) surface
JETP Letters, 2009
To prepare structure-ordered GaAs(001) surfaces at low temperatures, GaAs(001) surfaces coated with native oxides were exposed in an atomic hydrogen flow in the temperature range 280-450 ° C. The new Ga-enriched GaAs(001) surfaces with the (4 × 4) and (2 × 4)/c(2 × 8) reconstructions were prepared and studied by the methods of X-ray photoelectron spectroscopy, low-energy electron diffraction, and high-resolution characteristic electron energy loss spectroscopy. For the GaAs(001)-(2 × 4) surface, the structure of the Ga-stabilized surface has been proposed and ab initio computed within the (2 × 4) Ga-trimer unit cell model.
Atomic and electronic structures of GaAs (001) surface
Russian Physics Journal, 2006
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.
Theory of the (3×2) reconstruction of the GaAs(001) surface
Materials Science and Engineering: B, 1999
We discuss an ab initio density functional theory investigation of a (3 ×2) reconstruction of the Ga-rich GaAs(001) surface. Recent experiments identified this new reconstruction as a stable surface of epitaxially grown GaAs doped with indium or carbon (L. Li, et al., Appl. Phys. A 66 (1998) S501; L. Li, et al., Ultramicroscopy 73 (1998) 229). Using our recently developed real-space pseudopotential density functional code, we investigate this (3 × 2) reconstruction and evaluate stabilization mechanisms for the model proposed by the experimentalists, which does not satisfy the electron counting rule. In order to study the effect of In substitution, we consider the dependence of the surface energies of competing reconstructions on surface strain and relative chemical potentials. The effects of carbon substitution are modeled using a charged (3 ×2) reconstruction. These studies support and clarify the proposed structure and stabilization mechanisms. We provide a simple physical explanation for the behavior of the surface energy of the (3 ×2) reconstruction.
GaAs(001) surface reconstructions: geometries, chemical bonding and optical properties
Applied Surface Science, 2002
We re-examine the GaAs(0 0 1) surface by means of first-principles calculations based on a real-space multigrid method. The cð4 Â 4Þ; ð2 Â 4Þ and ð4 Â 2Þ surface reconstructions minimize the surface energy for anion-rich, stoichiometric and cation-rich surfaces, respectively. Structural models proposed in the literature to explain the Ga-rich GaAs(0 0 1) ð4 Â 6Þ surface are dismissed on energetic grounds. The electronic properties of the novel zð4 Â 2Þ structure are discussed in detail. We calculate the reflectance anisotropy of the energetically most favoured surfaces. A strong influence of the surface geometry on the optical anisotropy is found. #
2002
Ga-rich GaAs (001) surfaces are successfully observed during high-temperature annealing by scanning tunneling microscopy (STM). With a substrate temperature of 550 C, reflection high-energy diffraction patterns and reflectance anisotropy spectra confirm a (4x2) Ga-stabilized surface. STM images clearly show alteration of the surface reconstructions while scanning. It is postulated that detaching and attaching of Ga adatoms may be the cause
Surface phase diagram of (2×4) and (4×2) reconstructions of GaAs(001)
Physical Review B, 2000
Total-energy calculations for a series of (2ϫ4) and (4ϫ2) reconstructed GaAs͑001͒ surfaces not included in previous theoretical studies are presented. A (2ϫ4) surface model containing single anion dimers in the first and third atomic layers is predicted for a balanced surface stoichiometry. It is more stable than the two-Asdimer ␣ structure assumed previously, due to its lower electrostatic energy. Our results for the (4ϫ2) reconstructed surface confirm the two-Ga-dimer 2 structure suggested by Biegelsen and co-workers. Nearly degenerate in energy, however, are mixed Ga-As dimers adsorbed on a Ga-terminated substrate.
Direct real-space imaging of the c(2×8)∕(2×4) GaAs (001) surface structure
Physical Review B, 2007
We have performed frequency-modulated atomic-force microscopy (FM-AFM) on the c(2×8)/(2×4) GaAs (001) surface obtained from the c(8×2)/(4×6) surface by exposing it to As2 gas and annealing. Highly resolved interaction patterns reflect prevailing surface dimer pairs consistent with a so-called beta2 structure, but more rare motifs characteristic of alpha2 and beta structures are also seen. Atoms of the dimers interact with
GaAs(001) Surface under Conditions of Low As Pressure: Evidence for a Novel Surface Geometry
Physical Review Letters, 2000
Using density-functional theory we identify a new low-energy structure for GaAs(001) in an As-poor environment. The discovered geometry is qualitatively different from the usual surface-dimer based reconstructions of III-V semiconductor (001) surfaces. The stability of the new structure, which has a c͑8 3 2͒ periodicity, is explained in terms of bond saturation and favorable electrostatic interactions between surface atoms. Simulated scanning tunneling microscopy images are in good agreement with experimental data, and a low-energy electron diffraction analysis supports the theoretical prediction. PACS numbers: 68.35.Bs, 61.14.Hg, 68.35.Md, 73.20.At III-V semiconductors play an increasing role in microelectronics, such as light-emitting diodes and high frequency, low noise devices for mobile phones, and are important candidates for the development of devices in the emerging field of spin electronics. The knowledge of the surface atomic structure is a prerequisite to achieve understanding and controlling of the surface or interface electronic properties. As we will show below, however, up to date analyses of surface structures of III-V semiconductors are hindered by some prejudice on the type of structures considered. For an example of the GaAs(001) surface, we show the existence of a new type of surface reconstruction.
STM/nc-AFM investigation of (n×6) reconstructed GaAs(001) surface
Surface Science, 2003
We have investigated the n  6 reconstructed GaAs(0 0 1) surface with scanning tunneling and non-contact atomic force microscopy techniques (STM/nc-AFM). For the first time atomically resolved nc-AFM images of that surface are shown. The images confirm the presence of rows of arsenic dimers in the topmost layer as predicted by the current model of n  6 reconstructed surface. However, in contrast to previous reports we found that postulated As dimer sites are not fully occupied. Moreover, the images suggest that Â6 symmetry is present on the surface even in absence of the dimers. We show that due to probing of different surface properties nc-AFM and STM are complementary tools for complex surfaces investigation.