Mechanisms of surface alloy segregation on faceted core-shell nanowire growth

Zhang, Qian; Voorhees, Peter W.; Davis, Stephen H.

doi:10.1016/j.jmps.2016.12.005

Cited by 12 publications

(18 citation statements)

References 15 publications

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“…These problems are solved in [ 7 ] and [ 8 ], respectively. For simplicity, at first a pure material is deposited around the hexagonal core to investigate the mechanisms governing the morphological evolution.…”

Section: Resultsmentioning

confidence: 99%

“…It is obvious that a model assuming pure materials cannot address the mechanisms leading to the non-homogeneous distribution of Al in the shell. A two-dimensional fully faceted model [ 8 ] was developed for the growth of the shell with an A x B 1− x (Al x Ga 1− x As) alloy on a hexagonal core. Surface morphology and composition on the i -th facet evolve as…”

Section: Resultsmentioning

confidence: 99%

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Modeling of the growth of GaAs–AlGaAs core–shell nanowires

Zhang¹,

Voorhees²,

Davis³

2017

Beilstein J. Nanotechnol.

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Heterostructured GaAs–AlGaAs core–shell nanowires with have attracted much attention because of their significant advantages and great potential for creating high performance nanophotonics and nanoelectronics. The spontaneous formation of Al-rich stripes along certain crystallographic directions and quantum dots near the apexes of the shell are observed in AlGaAs shells. Controlling the formation of these core–shell heterostructures remains challenging. A two-dimensional model valid on the wire cross section, that accounts for capillarity in the faceted surface limit and deposition has been developed for the evolution of the shell morphology and concentration in AlxGa1− xAs alloys. The model includes a completely faceted shell–vapor interface. The objective is to understand the mechanisms of the formation of the radial heterostructures (Al-rich stripes and Al-poor quantum dots) in the nanowire shell. There are two issues that need to be understood. One is the mechanism responsible for the morphological evolution of the shells. Analysis and simulation results suggest that deposition introduces facets not present on the equilibrium Wulff shapes. A balance between diffusion and deposition yields the small facets with sizes varying slowly over time, which yield stripe structures, whereas deposition-dominated growth can lead to quantum-dot structures observed in experiments. There is no self-limiting facet size in this case. The other issue is the mechanism responsible for the segregation of Al atoms in the shells. It is found that the mobility difference of the atoms on the {112} and {110} facets together determine the non-uniform concentration of the atoms in the shell. In particular, even though the mobility of Al on {110} facets is smaller than that of Ga, Al-rich stripes are predicted to form along the {112} facets when the difference of the mobilities of Al and Ga atoms is sufficiently large on {112} facets. As the size of the shell increases, deposition becomes more important. The Al-poor dots are obtained at the apices of {112} facets, if the attachment rate of Al atoms is smaller there.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Modeling of the growth of GaAs–AlGaAs core–shell nanowires

Zhang¹,

Voorhees²,

Davis³

2017

Beilstein J. Nanotechnol.

Self Cite

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show abstract

“…[26] after the map onto a planar geometry and the application of SSA, and using a more convenient and standardized notations. Equations (9) and (10) [26], where the right-hand sides are certain functions of the surface orientation angle θ; this, and the inclusion of the anisotropy terms in the chemical potentials µ A and µ B introduce the anisotropy into the model of Ref. [26].…”

Section: A Model Equationsmentioning

confidence: 99%

“…Equations (9) and (10) [26], where the right-hand sides are certain functions of the surface orientation angle θ; this, and the inclusion of the anisotropy terms in the chemical potentials µ A and µ B introduce the anisotropy into the model of Ref. [26]. Due to abundance of other important physical effects and the associated parameters whose role is seldom brought to light and thus remains unclear, in this paper we choose not to study the anisotropy effects, thus γ B are constants.…”

Section: A Model Equationsmentioning

confidence: 99%

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Modeling solid-state dewetting of a single-crystal binary alloy thin films

Khenner

2018

Journal of Applied Physics

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Dewetting of a binary alloy thin film is studied using a continuum many-parameter model that accounts for the surface and bulk diffusion, the bulk phase separation, the surface segregation and the particles formation. Analytical solution is found for the quasistatic equilibrium concentration of a surface-segregated atomic species. This solution is factored into the nonlinear and coupled evolution PDEs for the bulk composition and surface morphology. Stability of a planar film surface with respect to small perturbations of the shape and composition is analyzed, revealing the dependence of the particles size on major physical parameters. Computations show various scenarios of the particles formation and the redistribution of the alloy components inside the particles and on their surface. In most situations, for the alloy film composed initially of 50% A and 50% B atoms, a core-shell particles are formed, and they are located atop a wetting layer that is modestly rich in the B phase. Then the particles shell is the nanometric segregated layer of the A phase, and the core is the alloy that is modestly rich in the A phase.

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Moiré-regulated composition evolution kinetics of bicomponent nanoclusters

Khenner

2024

J Nanopart Res

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Mechanisms of surface alloy segregation on faceted core-shell nanowire growth

Cited by 12 publications

References 15 publications

Modeling of the growth of GaAs–AlGaAs core–shell nanowires

Modeling of the growth of GaAs–AlGaAs core–shell nanowires

Modeling solid-state dewetting of a single-crystal binary alloy thin films

Moiré-regulated composition evolution kinetics of bicomponent nanoclusters

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