Kinetics in Surface Reconstructions on GaAs(001)

Ohtake, Akihiro; Kocán, Pavel; Nakamura, Jun; Natori, Akiko; Koguchi, Nobuyuki

doi:10.1103/physrevlett.92.236105

Cited by 80 publications

(66 citation statements)

References 27 publications

(21 reference statements)

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“…Here, the density of the droplets (and consequently that of the GaAs crystals) is 2 × 10 8 cm −2 ; a low density is desired in order to obtain the photoluminescence (PL) from a single structure. The supplied Ga is less than the well known As coverage of a c(4 × 4) surface (1.75ML) [15]; yet, Ga droplet formation with 1.5 MLs of Ga is possible, depending on the surface reconstruction (the As coverage is 1.0 ML for a c(4×4)-α surface [16]). Next, the Ga droplets are crystallized into GaAs The average base size and height of each QD is 45 (± 3) nm and 10 (± 2) nm, respectively, and are separated by an average distance of 39 (± 2) nm between their apexes, as estimated from AFM measurements.…”

mentioning

confidence: 99%

Self-assembly of laterally aligned GaAs quantum dot pairs

Yamagiwa

Mano

Kuroda

et al. 2006

Applied Physics Letters

115

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We report the fabrication of self-assembled, strain-free GaAs/Al0.27Ga0.73As quantum dot pairs which are laterally aligned in the growth plane, utilizing the droplet epitaxy technique and the anisotropic surface potentials of the GaAs (100) surface for the migration of Ga adatoms. Photoluminescence spectra from a single quantum dot pair, consisting of a doublet, have been observed. Finite element energy level calculations of a model quantum dot pair are also presented.When two semiconductor quantum dots (QDs), which can each spatially confine an individual carrier in a discrete energy level, are in close proximity to each other, these carriers begin to interact with each other. Specifically, the wavefunctions of the carriers confined in each QD of the QD pair (QDP) begin to overlap, resulting in an efficient carrier tunneling [1,2], and the wavefunctions may become admixed to form molecular orbital states. Moreover, resonance in the optical transition energies leads to the formation of a coupled QDP via dipole-dipole interactions [3,4,5]. Proposals for using such a coupling in quantum information processing have been brought forth [6,7]. To this end, various semiconductor QDPs have been fabricated and studied, such as coupled QDs grown by cleaved edge quantum well overgrowth [1], vertically-aligned QDs grown by StranskiKrastanow epitaxy incorporating an indium-flush procedure [2,4], and interface QDs formed in a quantum well [3]. In this work we demonstrate the fabrication of self-assembled, laterally aligned GaAs/Al 0.27 Ga 0.73 As QDP structures by droplet epitaxy: Droplet epitaxy is a nonconventional growth technique for the self-assembly of high quality nanostructures with lattice-matched materials, making possible the growth of nanostructures with various structural characteristics, such as QDs [8,9,10], quantum rings (QRs) [11], and concentric double QRs [12,13]. Here we observe the formation of laterally aligned GaAs QDPs by accurately selecting the As 4 flux during crystallization. Within relevant conditions, the nanocrystals show a remarkable shape like a double summit, reflecting the anisotropic surface potentials of the GaAs (100) surface. To gain insight into the interactions between the carriers confined in such a structure, we study the QDP single-structure optical properties. We further consider the electronic structure of a model QDP via energy level calculations requiring no inclusion of strain.The samples are grown by droplet epitaxy using a molecular beam epitaxy system with elemental sources and a valved As source, which enables the accurate control of the As 4 flux.

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confidence: 99%

Self-assembly of laterally aligned GaAs quantum dot pairs

Yamagiwa

Mano

Kuroda

et al. 2006

Applied Physics Letters

115

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“…This produces a moiré pattern of the hexagonal systems in the graphene/Ir(111) system, which corresponds to a 2D superstructure having a supercell with a (10 × 10) graphene lattice resting on top of a (9 × 9) Ir structure [390]. When about 0.01 ML of Ir is deposited on the graphene/Ir(111), Ir nanoclusters are formed on the graphene sheet at the locations where carbon atoms in the graphene sheet are in the atop positions, and sp 2 -sp 3 rehybridization occurs simultaneously on the carbon atoms covered by the Ir clusters [366]. Upon sp 2 -sp 3 rehybridization, the carbon atoms under an Ir cluster become sp 3 -coordinated, and they are sp 3 chemically bonded alternately with an Ir atom above in the cluster and below in the Ir surface.…”

Section: Structural Transformation From An Epitaxial Thin Film To a 3mentioning

confidence: 99%

“…• C under As-rich conditions, epitaxial growth of an InAs film usually starts from the bare GaAs(001) surface reconstructed in c(4 × 4) symmetry [279,280,364,365], which is characterized by blocks of three As ad-dimers sitting on top of a complete surface As layer [366,367]. These As ad-dimers at the topmost layer place the surface under tensile strain in both the [110] and [110] crystalline directions [279,280] because of stretching of the back-bonds of these ad-dimers, as well as the significantly short bond length between the two atoms in the ad-dimers.…”

Section: Formation Of Inas Wl On Gaas(001)mentioning

confidence: 99%

Self-assembly of InAs quantum dots on GaAs(001) by molecular beam epitaxy

Jin

2015

Front. Phys.

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Currently, the nature of self-assembly of three-dimensional epitaxial islands or quantum dots (QDs) in a lattice-mismatched heteroepitaxial growth system, such as InAs/GaAs(001) and Ge/Si(001) as fabricated by molecular beam epitaxy (MBE), is still puzzling. The purpose of this article is to discuss how the self-assembly of InAs QDs in MBE InAs/GaAs(001) should be properly understood in atomic scale. First, the conventional kinetic theories that have traditionally been used to interpret QD self-assembly in heteroepitaxial growth with a significant lattice mismatch are reviewed briefly by examining the literature of the past two decades. Second, based on their own experimental data, the authors point out that InAs QD self-assembly can proceed in distinctly different kinetic ways depending on the growth conditions and so cannot be framed within a universal kinetic theory, and, furthermore, that the process may be transient, or the time required for a QD to grow to maturity may be significantly short, which is obviously inconsistent with conventional kinetic theories. Third, the authors point out that, in all of these conventional theories, two well-established experimental observations have been overlooked: i) A large number of “floating” indium atoms are present on the growing surface in MBE InAs/GaAs(001); ii) an elastically strained InAs film on the GaAs(001) substrate should be mechanically unstable. These two well-established experimental facts may be highly relevant and should be taken into account in interpreting InAs QD formation. Finally, the authors speculate that the formation of an InAs QD is more likely to be a collective event involving a large number of both indium and arsenic atoms simultaneously or, alternatively, a morphological/structural transformation in which a single atomic InAs sheet is transformed into a three-dimensional InAs island, accompanied by the rehybridization from the sp 2-bonded to sp 3-bonded atomic configuration of both indium and arsenic elements in the heteroepitaxial growth system.

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“…14,[16][17][18][19][20] The structure models of the three reconstructions investigated here and their respective nucleophilic and/or electrophilic surface sites are depicted in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

“…1. Structure model of pyrrole and structure models of the different GaAs(001) reconstructions according to Schmidt et al 28 and Ohtake et al 14,18 The c(4 × 4) surface provides only nucleophilic surface sites while the (4 × 2) and the (6 × 6) surfaces exhibit both nucleophilic and electrophilic surface sites.…”

Section: Introductionmentioning

confidence: 99%

Electrophilic surface sites as precondition for the chemisorption of pyrrole on GaAs(001) surfaces

Bruhn

Fimland

Vogt

2015

The Journal of Chemical Physics

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Originally published as:Bruhn, T., Fimland, B.-O., Vogt, P. (2015): Electrophilic surface sites as precondition for the chemisorption of pyrrole on GaAs (001) We report how the presence of electrophilic surface sites influences the adsorption mechanism of pyrrole on GaAs(001) surfaces. For this purpose, we have investigated the adsorption behavior of pyrrole on different GaAs(001) reconstructions with different stoichiometries and thus different surface chemistries. The interfaces were characterized by x-ray photoelectron spectroscopy, scanning tunneling microscopy, and by reflectance anisotropy spectroscopy in a spectral range between 1.5 and 5 eV. On the As-rich c(4 × 4) reconstruction that exhibits only nucleophilic surface sites, pyrrole was found to physisorb on the surface without any significant modification of the structural and electronic properties of the surface. On the Ga-rich GaAs(001)-(4 × 2)/(6 × 6) reconstructions which exhibit nucleophilic as well as electrophilic surface sites, pyrrole was found to form stable covalent bonds mainly to the electrophilic (charge deficient) Ga atoms of the surface. These results clearly demonstrate that the existence of electrophilic surface sites is a crucial precondition for the chemisorption of pyrrole on GaAs(001) surfaces. C 2015 AIP Publishing LLC. [http://dx

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Kinetics in Surface Reconstructions on GaAs(001)

Cited by 80 publications

References 27 publications

Self-assembly of laterally aligned GaAs quantum dot pairs

Self-assembly of laterally aligned GaAs quantum dot pairs

Self-assembly of InAs quantum dots on GaAs(001) by molecular beam epitaxy

Electrophilic surface sites as precondition for the chemisorption of pyrrole on GaAs(001) surfaces

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