Surface-shift low-energy photoelectron diffraction: Clean and hydrogenated GaAs(110) surface-structure relaxation (original) (raw)
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Physical Review B, 1995
Metastable deexcitation spectroscopy was applied to study the surface valence electronic structure of clean cleaved GaAs(110). Metastable deexcitation spectroscopy was flanked by angle-resolved photoemission. An effective surface density of states was derived from the experimental spectrum through deconvolution. Two groups of states were observed in the 0 -4 and 5 -8 eV range of binding energy, respectively. These features were ascribed to emission from surface states. A plane-by-plane tight-binding density-of-states calculation was performed. More quantitative insights were obtained by comparing experimental and theoretical results. The most prominent feature of the first group of states of deconvolution was assigned to surface state As. Contributions from states A4, A3 A1, and A2 were also observed. The doublet of the second group of features was identified with Cq and C1. Relative amplitudes of effective surface density of states were related to surface charge density.
Theoretical Study of the Surface Optical Properties of Clean and Hydrogenated GaAs(110)
physica status solidi (a), 1999
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Surface Science, 1996
The valence and core electronic structure of the sputtered and annealed 1 × 1 periodic GaAs(311)A surface has been studied by angle-resolved photoelectron spectroscopy. Five surface bands are identified and their dispersions along high symmetry lines in the surface Brillouin zone are mapped out. While electron-counting indicates a metallic surface, the experiment show no evidence for partly occupied surface bands. Analysis of the core level spectra reveals one As and two Ga surface shifted components. The results are discussed in terms of surface geometry models.
The morphology of high-index GaAs surfaces
Applied Surface Science, 2000
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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. #
Physical Review B, 1992
We present a comprehensive study of epitaxially grown and As-coated GaAs(100) surfaces as a function of As desorption temperature and background pressure. We have used low-energy electron diffraction to determine surface reconstruction, and core-level and valence-band soft-x-ray photoemission spectroscopy to perform chemical and electronic characterization of these surfaces. We find gradual changes in surface geometry and composition, and a limited (-120 meV) Fermi-level movement over numerous reconstructions in the 250-650'C annealing temperature range. The surface ionization potential and work function exhibit large changes between different surface reconstructions. In conjunction with other techniques, work-function measurements present evidence of surface inhomogeneity for many of the desorption temperatures and surface reconstructions. This inhomogeneity appears related to the existence of differently reconstructed patches on the surface. Our results emphasize the complexity of reconstructed GaAs(100) surfaces and the advantages of a multiple-technique approach for their characterization.
Structure and energetics of Ga-rich GaAs() surfaces
Surface Science, 2002
The atomic structures and energies of Ga-rich GaAs(0 0 1) surface reconstructions are examined by means of firstprinciples total-energy calculations based on a real-space multigrid method. Our calculations confirm the existence of the novel f(4 Â 2) structure suggested by Lee et al. [Phys. Rev. Lett. 85 (2000) 3890]. (4 Â 6) surface reconstructions suggested to explain STM experiments are found to be unstable. The calculations indicate that the adsorption of Ga adatoms in the trenches of the f(4 Â 2) surface could possibly explain the observed structures. The diffusion of Ga/As adatoms on the Ga-rich GaAs surface is predicted to be anisotropic and should preferably take place parallel to the [1 1 0]/[1 1 1 0] direction, respectively. Ó