Optical anisotropy of ordered Sb layers on III-V (110) surfaces

Esser, N.; Richter, Wolfgang; Resch‐Esser, U.; Chiaradia, P.; Goletti, C.; Moretti, Luca

doi:10.1080/01418639408240225

Cited by 14 publications

(3 citation statements)

References 26 publications

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“…Model I is no equilibrium structure, independent of the Sb and Ga chemical potentials.of the optical anisotropy over the entire spectral range which can be understood as the consequence of breaking the surface As dimer bonds upon Sb adsorption. A broad positive anisotropy around 4-4.5 eV develops after deposition of additional Sb (curve c) related to the optical properties of the thin Sb overlayer[24]. New anisotropy features arise with the ordering process induced by annealing: For the intermediate annealing step, a negative anisotropy around 2 eV and a positive feature around 4.2 eV develop(d).…”

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Atomic Structure of the Sb-Stabilized GaAs(100)-(2×4) Surface

et al. 1996

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The microscopic structure of the Sb stabilized GaAs(100)-(2 3 4) surfaces is investigated combining reflectance anisotropy spectroscopy with first-principles total energy minimization and tight-binding calculations of optical properties. We show that the model accepted so far, containing three Sb dimers in the outermost layer, is not a stable surface geometry. Our results reveal a coexistence of Sb and Ga dimers on the Sb-stabilized ͑2 3 4͒ surface. [S0031-9007(96)01679-1] PACS numbers: 68.35.Bs, 68.35.Md, 78.30.Fs, 78.66.Fd Understanding of the surface atomic structures and their modification through deposition of foreign atoms is crucial for both science and technology. In particular, the adsorption of group-V elements on (100) faces of III-V compound semiconductors is technologically important for the III-V heteroepitaxy [1]. Especially the adsorption of Sb on GaAs(100) has attracted interest due to the formation of an exceptionally abrupt interface [1,2] and the possible use of Sb as surfactant for metal growth on GaAs(100) [3,4]. Soft x-ray photoemission spectroscopy (SXPS), Auger electron spectroscopy (AES), and electron diffraction [LEED and reflection high-energy electron diffraction (RHEED), respectively] studies have shown that by Sb deposition on GaAs(100) and subsequent annealing a well-ordered ͑2 3 4͒ reconstruction is formed even at temperatures much higher than for the clean, As-terminated surface, due to stabilization by Sb dimers [1,5,6].Based on SXPS data and on the ͑2 3 4͒ RHEED pattern a first structural model for the Sb-induced reconstruction was suggested [1]. This model, based on three Sb dimers per surface unit cell, was constructed in analogy to the so-called GaAs(100)b͑2 3 4͒ structure, widely used in the past to describe As-terminated GaAs(100)-͑2 3 4͒ surfaces [7,8]. For the clean GaAs(100)-͑2 3 4͒ surface, however, recent experimental and theoretical studies have demonstrated that the equilibrium structure contains only two As dimers per unit cell in the topmost atomic layer, denoted as b2͑2 3 4͒ structure [9-12]. As shown in Ref. [9], the electrostatic interaction between the negatively charged surface As dimers destabilizes the three-dimer compared to the two-dimer structure. The same argument should hold if the As dimers are substituted by another group-V element like Sb, thus questioning the validity of the suggested structure for the Sb-stabilized ͑2 3 4͒ GaAs(100) surface. Meanwhile, x-ray standing wave (XSW) experiments [13] confirmed the existence of Sb dimers on the surface; however, conclusive results about the validity of the three-Sb-dimer model [1] were not obtained.The present study is aimed at the determination of the atomic structure of the Sb-stabilized GaAs(100)-͑2 3 4͒ surface, using a novel approach to investigate microscopic surface properties based on the surface optical response. We apply reflectance anisotropy spectroscopy (RAS), ab initio total-energy minimization (TE), and tightbinding (TB) calculations of optical properties to study the precise surface ge...

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Atomic Structure of the Sb-Stabilized GaAs(100)-(2×4) Surface

et al. 1996

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“…This would be consistent with the fact that the energetic position of the minimum scales with the bulk critical points of the different substrates. This model is supported by the fact that other adsorbates forming chains along the [110] direction (such as Sb) lead to a minimum in the RAS around 2 eV as well [29,30]. On the other hand, it is hard to understand why strain should effect the RAS in a region away from bulk critical points.…”

Section: Comparison Of the Different Substratesmentioning

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Optical anisotropy of Cs nanostructures on III–V(110) surfaces

Fleischer

Bussetti

Goletti

et al. 2004

J. Phys.: Condens. Matter

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We present reflectance anisotropy spectra in the energy range 1.0-5.5 eV, measured for cleaved III-V surfaces after adsorption of caesium. In such a system Cs forms one-dimensional wire-like structures at low Cs coverages ( 1 ML). The formation of these Cs wires leads to characteristic changes in the reflectance anisotropy spectra of the cleaved surface such as a minimum between the E 0 and E 1 bulk critical points of the substrate. For higher coverages the development of a two-dimensional layer can be optically monitored, as can the gradual transition to a three-dimensional disordered layer close to the saturation coverage.

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“…[38][39][40][41][42][43][44][45][46][47] This draws a parallel to the conjugated polymer literature where hole-transporting macromolecules dominated the research landscape; however, it was clear in the conjugated polymer regime previously, and it is clear in the radical polymer community now, that developing preferentially-reduced (i.e., n-type) open-shell macromolecules will be of critical importance in the near future. 3,8,48,49 To address this gap, here we design, synthesize, and characterize the electronic and electrochemical properties of the first low glass transition temperature, n-type (i.e., preferentiallyreduced) radical polymer. Specifically, we synthesized a radical polymer with a flexible polysiloxane backbone bearing galvinoxyl radical moieties, poly [2,6-…”

Section: Introductionmentioning

confidence: 99%