Coupled evolution of composition and morphology in a faceted three-dimensional quantum dot

Vastola, G.; Shenoy, Vivek B.; Guo, Junyan; Zhang, Yong‐Wei

doi:10.1103/physrevb.84.035432

Cited by 18 publications

(19 citation statements)

References 29 publications

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“…Admittedly, these constitute the two extremes, and intermediate cases like partially segregated alloy realizations are not addressed in this work. The uniform alloy composition considered here is expected under high growth rate conditions, where the landing atoms on the surface do not have time to segregate into binary compounds, as they quickly get covered by the next layer [41]. The rationale behind the selection of these two cases is based on their distinct strain, and hence quadrupolar characteristics [20].…”

Section: A Test Qdsmentioning

confidence: 99%

Nuclear magnetic resonance inverse spectra of InGaAs quantum dots: Atomistic level structural information

2014

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A wealth of atomistic information is contained within a self-assembled quantum dot (QD), associated with its chemical composition and the growth history. In the presence of quadrupolar nuclei, as in InGaAs QDs, much of this is inherited to nuclear spins via the coupling between the strain within the polar lattice and the electric quadrupole moments of the nuclei. Here, we present a computational study of the recently introduced inverse spectra nuclear magnetic resonance technique to assess its suitability for extracting such structural information. We observe marked spectral differences between the compound InAs and alloy InGaAs QDs. These are linked to the local biaxial and shear strains, and the local bonding configurations. The cation alloying plays a crucial role especially for the arsenic nuclei. The isotopic line profiles also largely differ among nuclear species: While the central transition of the gallium isotopes have a narrow linewidth, those of arsenic and indium are much broader and oppositely skewed with respect to each other. The statistical distributions of electric field gradient (EFG) parameters of the nuclei within the QD are analyzed. The consequences of various EFG axial orientation characteristics are discussed. Finally, the possibility of suppressing the first-order quadrupolar shifts is demonstrated by simply tilting the sample with respect to the static magnetic field. © 2014 American Physical Society

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Section: A Test Qdsmentioning

confidence: 99%

Nuclear magnetic resonance inverse spectra of InGaAs quantum dots: Atomistic level structural information

2014

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“…Moreover, since GaAs/AlGaAs nanowire system is a coherent system without lattice misfit strain, only surface energy is considered in our model. However, if the system is strained, elastic energy has to be taken into account (see also Shenoy (2011), Vastola (2011)). In addition, as mentioned in Heiss et al (2013), in the experiments, the GaAs core is first obtained at a given temperature.…”

Section: Introductionmentioning

confidence: 99%

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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“…27 For the case of d, our numerical estimation is in agreement with the previous work. 20,28 Starting from the value of b that best fits the experiments, and considering the experimental growth rate of 0:02 nm=s, 19 we estimate the value of K to be K ¼ 2 Á 10 À4 nm=s. Since strain does not play a key role in the growth of nanowires, as com-pared with thin films, 29 the numerical value for K is reliable through a wide range of compositions.…”

Section: Resultsmentioning

confidence: 99%

Controlling the interface composition of core-shell and axial heterojunction nanowires

Vastola

Shenoy

Zhang

2012

Journal of Applied Physics

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Composition profile across an interface in a core/shell or axial heterojunction nanowire often plays an important role in dictating its electronic, optical and magnetic properties. The control of composition profiles to achieve optimal performance still remains a challenge. In the present work, we formulate a theoretical model which accounts for three key factors that completely control the interface composition profile: the deposition flux of individual components, the atomic exchange rate between the surface and its sub-surface layer, and the thermodynamic driving force for surface segregation. We validate the model by matching its predictions with the experimental results for thin film growth. We then apply the model to the growth of core/shell and axial heterojunction nanowires and show that both abrupt and diffuse interface composition profiles can be achieved by tuning the growth parameters, providing a predictive approach for controlling interface composition distribution. V C 2012 American Institute of Physics. [http://dx.

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Coupled evolution of composition and morphology in a faceted three-dimensional quantum dot

Cited by 18 publications

References 29 publications

Nuclear magnetic resonance inverse spectra of InGaAs quantum dots: Atomistic level structural information

Nuclear magnetic resonance inverse spectra of InGaAs quantum dots: Atomistic level structural information

Mechanisms of morphological evolution on faceted core–shell nanowire surfaces

Controlling the interface composition of core-shell and axial heterojunction nanowires

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