Simulation of self-assembled compositional core-shell structures in In<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mi>x</mml:mi></mml:msub></mml:math>Ga<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:math>N nanowires

Niu, Xiaobin; Stringfellow, G. B.; Lee, Young Ju; Liu, Feng

doi:10.1103/physrevb.85.165316

Cited by 9 publications

(7 citation statements)

References 34 publications

(50 reference statements)

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“…Also, in this continuous fully faceted model, the behaviour of each facets is counted in average. Thus, influence of different growth modes, such as layer-by-layer and step flow mentioned in Niu et al (2012), on the facet morphology is beyond the discussion in this paper.…”

Section: Introductionmentioning

confidence: 95%

Mechanisms of morphological evolution on faceted core–shell nanowire surfaces

Zhang

Aqua

Voorhees

et al. 2016

Journal of the Mechanics and Physics of Solids

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Core-shell nanowires with radial heterostructures hold great promise in photonic and electronic applications and controlling the formation of these heterostructures in the core-shell configuration remains a challenge. Recently, GaAs nanowires have been used as substrates to create AlGaAs shells. The deposition of the AlGaAs layer leads to the spontaneous formation of Al-rich stripes along certain crystallographic directions and quantum dots/wires near the apexes of the shell. A general two-dimensional model has been developed for the motion of the faceted solid-vapor interfaces for pure materials that accounts for capillarity and deposition. With this model, the growth processes and morphological evolution of shells of nanowires around hexagonal cores (six small facets {112} in the corners of six equivalent facets {110}) are investigated in detail both analytically and numerically. It is found that deposition can yield facets that are not present on the Wulff shape. These small facets can have slowly timevarying sizes that can lead to stripe structures and quantum dots/wires depending on the balances between diffusion and deposition. The effects of deposition rates and polarity (or asymmetry) on planes {112} on the development of the configurations of nanowires are discussed. The numerical results are compared with experimental results giving almost quantitative agreement, despite the fact that only pure materials are treated herein whereas the experiments deal with alloys.

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Section: Introductionmentioning

confidence: 95%

Mechanisms of morphological evolution on faceted core–shell nanowire surfaces

Zhang

Aqua

Voorhees

et al. 2016

Journal of the Mechanics and Physics of Solids

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“…Recently, much attention has been paid to ternary IIIA nitrides, including InGaN, InAlN, and AlGaN nanostructures, because their band gaps and lattice parameters can be engineered by tuning their compositions. − To obtain high crystal quality, nanostructures are often grown at elevated temperatures. However, instead of forming single-phase ternary alloy NRs, a core–shell structure is found in these self-induced NRs. ,− ,− Presently, most studies addressing formation of self-induced NRs depart from stipulating models relying on a thermodynamical equilibrium viewpoint and phase separation due to the immiscibility of a ternary alloy, which, in general, are not capable of explaining the formation of nanostructures of such complexity and diversity. For instance, AlGaN is miscible throughout the entire compositional range while a core–shell structure is still observed in self-indued NRs …”

Section: Introductionmentioning

confidence: 99%

“…However, instead of forming single-phase ternary alloy NRs, a core–shell structure is found in these self-induced NRs. 7 , 11 − 13 , 18 − 20 Presently, most studies addressing formation of self-induced NRs depart from stipulating models relying on a thermodynamical equilibrium viewpoint and phase separation due to the immiscibility of a ternary alloy, which, in general, are not capable of explaining the formation of nanostructures of such complexity and diversity. For instance, AlGaN is miscible throughout the entire compositional range while a core–shell structure is still observed in self-indued NRs.…”

Section: Introductionmentioning

confidence: 99%

Self-Induced Core–Shell InAlN Nanorods: Formation and Stability Unraveled by Ab Initio Simulations

et al. 2022

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By addressing precursor prevalence and energetics using the DFT-based synthetic growth concept (SGC), the formation mechanism of self-induced InAlN core−shell nanorods (NRs) synthesized by reactive magnetron sputter epitaxy (MSE) is explored. The characteristics of In-and Al-containing precursor species are evaluated considering the thermal conditions at a typical NR growth temperature of around 700 °C. The cohesive and dissociation energies of In-containing precursors are consistently lower than those of their Alcontaining counterparts, indicating that In-containing precursors are more weakly bonded and more prone to dissociation. Therefore, Incontaining species are expected to exhibit lower abundance in the NR growth environment. At increased growth temperatures, the depletion of In-based precursors is even more pronounced. A distinctive imbalance in the incorporation of Al-and In-containing precursor species (namely,

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“…In general, it is assumed that the GaN shell is formed by the radial overgrowth of the NWs during the deposition of the GaN barriers. However, some works have suggested that the formation of a narrower island in the center of the NWs can be energetically more favorable, so that the GaN shell is formed by the filling of the remaining lateral free space during the subsequent deposition steps, without any necessary radial growth of the NWs. , Another scenario suggested in the literature to explain the formation of the GaN shell is the possible spontaneous formation of a core–shell structure during the growth of the QDs due to a strain-driven segregation of the constituent binary compounds. , Furthermore, despite control in both, the chemistry (indium content) and shape of the QDs are critical for appropriately tuning the optoelectronic properties of these structures; very often the stacked QDs within the same NW show systematic changes in their shape from one QD to the next, even though they were grown under nominally identical conditions. ,, This change has been reported also for other lattice mismatched material systems such as (Al,Ga)N/GaN NWs or vertically self-aligned InAs quantum dots on GaAs planar substrates …”

mentioning

confidence: 99%

“…11,12 Another scenario suggested in the literature to explain the formation of the GaN shell is the possible spontaneous formation of a core−shell structure during the growth of the QDs due to a strain-driven segregation of the constituent binary compounds. 13,14 Furthermore, despite control in both, the chemistry (indium content) and shape of the QDs are critical for appropriately tuning the optoelectronic properties of these structures; very often the stacked QDs within the same NW show systematic changes in their shape from one QD to the next, even though they were grown under nominally identical conditions. 12,15,16 This change has been reported also for other lattice mismatched material systems such as (Al,Ga)N/GaN NWs 17 or vertically self-aligned InAs quantum dots on GaAs planar substrates.…”

mentioning

confidence: 99%

Strain Driven Shape Evolution of Stacked (In,Ga)N Quantum Disks Embedded in GaN Nanowires

et al. 2017

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The fabrication of nanowires with axial multiquantum wells or disks presenting a homogeneous size and shape distribution along the whole stack is still an unresolved challenge, despite being essential for narrowing their light emission bandwidth. In this work we demonstrate that the commonly observed change in the shape of the disks along the stacking direction proceeds in a systematic, predictable way. High- resolution transmission electron microscopy of stacked (In,Ga)N quantum discs embedded in GaN nanowires with diameters of ∼40 nm and lengths of ∼700 nm and finite element method calculations show that, contrary to what is normally assumed, this change is not related to the radial growth of the nanowires, which is shown to be negligible, but to the strain relaxation of the whole active region. A simple model is proposed to account for the experimental observations. The model assumes that each disk reaches an equilibrium shape that minimizes the overall energy of the system, given by the sum of the surface and strain energies of the disk itself and the barrier below. The strain state of the barrier is affected by the presence of the disk buried directly below in a way that depends on its shape. This gives rise to a cumulative process, which makes the aspect ratio of each quantum disk to be smaller compared to the disk grown just before, in qualitative agreement with the experimental observations. The obtained results imply that strain relaxation is an important factor to bear in mind for the design of multiquantum disks with controlled shape along the stacking direction in any lattice mismatched nanowire system.

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Simulation of self-assembled compositional core-shell structures in InxGa1−xN nanowires

Cited by 9 publications

References 34 publications

Mechanisms of morphological evolution on faceted core–shell nanowire surfaces

Mechanisms of morphological evolution on faceted core–shell nanowire surfaces

Self-Induced Core–Shell InAlN Nanorods: Formation and Stability Unraveled by Ab Initio Simulations

Strain Driven Shape Evolution of Stacked (In,Ga)N Quantum Disks Embedded in GaN Nanowires

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