Research

11 pages, 2502 KiB

Open AccessArticle

Reconsideration of Nanowire Growth Theory at Low Temperatures

by Vladimir G. Dubrovskii

Nanomaterials 2021, 11(9), 2378; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11092378 - 13 Sep 2021

Cited by 3 | Viewed by 1446

We present a growth model that describes the nanowire length and radius versus time in the absence of evaporation or scattering of semiconductor atoms (group III atoms in the case of III-V NWs) from the substrate, nanowire sidewalls or catalyst nanoparticle. The model [...] Read more.

We present a growth model that describes the nanowire length and radius versus time in the absence of evaporation or scattering of semiconductor atoms (group III atoms in the case of III-V NWs) from the substrate, nanowire sidewalls or catalyst nanoparticle. The model applies equally well to low-temperature metal-catalyzed or selective area growth of elemental or III-V nanowires on patterned substrates. Surface diffusion transport and radial growth on the nanowire sidewalls are carefully considered under the constraint of the total material balance, yielding some new effects. The nanowire growth process is shown to proceed in two steps. In the first step, the nanowire length increases linearly with time and is inversely proportional to the nanowire radius squared and the nanowire surface density, without radial growth. In the second step, the nanowire length obeys the Chini equation, resulting in a non-linear increase in length with time and radial growth. The nanowire radii converge to a stationary value in the large time limit, showing a kind of size-narrowing effect. The model fits the data on the growth kinetics of a single self-catalyzed GaAs nanowire on a Si substrate well. Full article

(This article belongs to the Special Issue Preparation and Application of Nanowires)

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7 pages, 1283 KiB

Open AccessEditor’s ChoiceArticle

Dynamics of Monolayer Growth in Vapor–Liquid–Solid GaAs Nanowires Based on Surface Energy Minimization

by Hadi Hijazi and Vladimir G. Dubrovskii

Nanomaterials 2021, 11(7), 1681; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11071681 - 26 Jun 2021

Viewed by 1472

Abstract

The vapor–liquid–solid growth of III-V nanowires proceeds via the mononuclear regime, where only one island nucleates in each nanowire monolayer. The expansion of the monolayer is governed by the surface energetics depending on the monolayer size. Here, we study theoretically the role of [...] Read more.

The vapor–liquid–solid growth of III-V nanowires proceeds via the mononuclear regime, where only one island nucleates in each nanowire monolayer. The expansion of the monolayer is governed by the surface energetics depending on the monolayer size. Here, we study theoretically the role of surface energy in determining the monolayer morphology at a given coverage. The optimal monolayer configuration is obtained by minimizing the surface energy at different coverages for a set of energetic constants relevant for GaAs nanowires. In contrast to what has been assumed so far in the growth modeling of III-V nanowires, we find that the monolayer expansion may not be a continuous process. Rather, some portions of the already formed monolayer may dissolve on one of its sides, with simultaneous growth proceeding on the other side. These results are important for fundamental understanding of vapor–liquid–solid growth at the atomic level and have potential impacts on the statistics within the nanowire ensembles, crystal phase, and doping properties of III-V nanowires. Full article

(This article belongs to the Special Issue Preparation and Application of Nanowires)

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12 pages, 4097 KiB

Open AccessArticle

Tailoring the Geometry of Bottom-Up Nanowires: Application to High Efficiency Single Photon Sources

by Dan Dalacu, Philip J. Poole and Robin L. Williams

Nanomaterials 2021, 11(5), 1201; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11051201 - 01 May 2021

Cited by 8 | Viewed by 2058

Abstract

For nanowire-based sources of non-classical light, the rate at which photons are generated and the ability to efficiently collect them are determined by the nanowire geometry. Using selective-area vapour-liquid-solid epitaxy, we show how it is possible to control the nanowire geometry and tailor [...] Read more.

For nanowire-based sources of non-classical light, the rate at which photons are generated and the ability to efficiently collect them are determined by the nanowire geometry. Using selective-area vapour-liquid-solid epitaxy, we show how it is possible to control the nanowire geometry and tailor it to optimise device performance. High efficiency single photon generation with negligible multi-photon emission is demonstrated using a quantum dot embedded in a nanowire having a geometry tailored to optimise both collection efficiency and emission rate. Full article

(This article belongs to the Special Issue Preparation and Application of Nanowires)

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9 pages, 3189 KiB

Open AccessEditor’s ChoiceArticle

Kinetics of Guided Growth of Horizontal GaN Nanowires on Flat and Faceted Sapphire Surfaces

by Amnon Rothman, Jaroslav Maniš, Vladimir G. Dubrovskii, Tomáš Šikola, Jindřich Mach and Ernesto Joselevich

Nanomaterials 2021, 11(3), 624; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11030624 - 03 Mar 2021

Cited by 3 | Viewed by 2142

Abstract

The bottom-up assembly of nanowires facilitates the control of their dimensions, structure, orientation and physical properties. Surface-guided growth of planar nanowires has been shown to enable their assembly and alignment on substrates during growth, thus eliminating the need for additional post-growth processes. However, [...] Read more.

The bottom-up assembly of nanowires facilitates the control of their dimensions, structure, orientation and physical properties. Surface-guided growth of planar nanowires has been shown to enable their assembly and alignment on substrates during growth, thus eliminating the need for additional post-growth processes. However, accurate control and understanding of the growth of the planar nanowires were achieved only recently, and only for ZnSe and ZnS nanowires. Here, we study the growth kinetics of surface-guided planar GaN nanowires on flat and faceted sapphire surfaces, based on the previous growth model. The data are fully consistent with the same model, presenting two limiting regimes—either the Gibbs–Thomson effect controlling the growth of the thinner nanowires or surface diffusion controlling the growth of thicker ones. The results are qualitatively compared with other semiconductors surface-guided planar nanowires materials, demonstrating the generality of the growth mechanism. The rational approach enabled by this general model provides better control of the nanowire (NW) dimensions and expands the range of materials systems and possible application of NW-based devices in nanotechnology. Full article

(This article belongs to the Special Issue Preparation and Application of Nanowires)

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13 pages, 2710 KiB

Open AccessEditor’s ChoiceArticle

Self-Catalyzed InSb/InAs Quantum Dot Nanowires

by Omer Arif, Valentina Zannier, Francesca Rossi, Daniele Ercolani, Fabio Beltram and Lucia Sorba

Nanomaterials 2021, 11(1), 179; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11010179 - 13 Jan 2021

Cited by 5 | Viewed by 2368

Abstract

The nanowire platform offers great opportunities for improving the quality and range of applications of semiconductor quantum wells and dots. Here, we present the self-catalyzed growth of InAs/InSb/InAs axial heterostructured nanowires with a single defect-free InSb quantum dot, on Si substrates, by chemical [...] Read more.

The nanowire platform offers great opportunities for improving the quality and range of applications of semiconductor quantum wells and dots. Here, we present the self-catalyzed growth of InAs/InSb/InAs axial heterostructured nanowires with a single defect-free InSb quantum dot, on Si substrates, by chemical beam epitaxy. A systematic variation of the growth parameters for the InAs top segment has been investigated and the resulting nanowire morphology analyzed. We found that the growth temperature strongly influences the axial and radial growth rates of the top InAs segment. As a consequence, we can reduce the InAs shell thickness around the InSb quantum dot by increasing the InAs growth temperature. Moreover, we observed that both axial and radial growth rates are enhanced by the As line pressure as long as the In droplet on the top of the nanowire is preserved. Finally, the time evolution of the diameter along the entire length of the nanowires allowed us to understand that there are two In diffusion paths contributing to the radial InAs growth and that the interplay of these two mechanisms together with the total length of the nanowires determine the final shape of the nanowires. This study provides insights in understanding the growth mechanisms of self-catalyzed InSb/InAs quantum dot nanowires, and our results can be extended also to the growth of other self-catalyzed heterostructured nanowires, providing useful guidelines for the realization of quantum structures with the desired morphology and properties. Full article

(This article belongs to the Special Issue Preparation and Application of Nanowires)

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8 pages, 5399 KiB

Open AccessEditor’s ChoiceArticle

Thermodynamics of the Vapor–Liquid–Solid Growth of Ternary III–V Nanowires in the Presence of Silicon

by Hadi Hijazi, Mohammed Zeghouane and Vladimir G. Dubrovskii

Nanomaterials 2021, 11(1), 83; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11010083 - 02 Jan 2021

Viewed by 2242

Abstract

Based on a thermodynamic model, we quantify the impact of adding silicon atoms to a catalyst droplet on the nucleation and growth of ternary III–V nanowires grown via the self-catalyzed vapor–liquid–solid process. Three technologically relevant ternaries are studied: InGaAs, AlGaAs and InGaN. For [...] Read more.

Based on a thermodynamic model, we quantify the impact of adding silicon atoms to a catalyst droplet on the nucleation and growth of ternary III–V nanowires grown via the self-catalyzed vapor–liquid–solid process. Three technologically relevant ternaries are studied: InGaAs, AlGaAs and InGaN. For As-based alloys, it is shown that adding silicon atoms to the droplet increases the nanowire nucleation probability, which can increase by several orders magnitude depending on the initial chemical composition of the catalyst. Conversely, silicon atoms are found to suppress the nucleation rate of InGaN nanowires of different compositions. These results can be useful for understanding and controlling the vapor–liquid–solid growth of ternary III–V nanowires on silicon substrates as well as their intentional doping with Si. Full article

(This article belongs to the Special Issue Preparation and Application of Nanowires)

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15 pages, 4408 KiB

Open AccessArticle

Role of Thermodynamics and Kinetics in the Composition of Ternary III-V Nanowires

by Egor D. Leshchenko and Jonas Johansson

Nanomaterials 2020, 10(12), 2553; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10122553 - 18 Dec 2020

Cited by 10 | Viewed by 1852

Abstract

We explain the composition of ternary nanowires nucleating from a quaternary liquid melt. The model we derive describes the evolution of the solid composition from the nucleated-limited composition to the kinetic one. The effect of the growth temperature, group V concentration and Au/III [...] Read more.

We explain the composition of ternary nanowires nucleating from a quaternary liquid melt. The model we derive describes the evolution of the solid composition from the nucleated-limited composition to the kinetic one. The effect of the growth temperature, group V concentration and Au/III concentration ratio on the solid-liquid dependence is studied. It has been shown that the solid composition increases with increasing temperature and Au concentration in the droplet at the fixed In/Ga concentration ratio. The model does not depend on the site of nucleation and the geometry of monolayer growth and is applicable for nucleation and growth on a facet with finite radius. The case of a steady-state (or final) solid composition is considered and discussed separately. While the nucleation-limited liquid-solid composition dependence contains the miscibility gap at relevant temperatures for growth of In_xGa_1−xAs NWs, the miscibility gap may be suppressed completely in the steady-state growth regime at high supersaturation. The theoretical results are compared with available experimental data via the combination of the here described solid-liquid and a simple kinetic liquid-vapor model. Full article

(This article belongs to the Special Issue Preparation and Application of Nanowires)

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12 pages, 2028 KiB

Open AccessEditor’s ChoiceArticle

Calculation of Hole Concentrations in Zn Doped GaAs Nanowires

by Jonas Johansson, Masoomeh Ghasemi, Sudhakar Sivakumar, Kilian Mergenthaler, Axel R. Persson, Wondwosen Metaferia and Martin H. Magnusson

Nanomaterials 2020, 10(12), 2524; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10122524 - 16 Dec 2020

Cited by 2 | Viewed by 2109

Abstract

We have previously demonstrated that we can grow p-type GaAs nanowires using Zn doping during gold catalyzed growth with aerotaxy. In this investigation, we show how to calculate the hole concentrations in such nanowires. We base the calculations on the Zhang–Northrup defect formation [...] Read more.

We have previously demonstrated that we can grow p-type GaAs nanowires using Zn doping during gold catalyzed growth with aerotaxy. In this investigation, we show how to calculate the hole concentrations in such nanowires. We base the calculations on the Zhang–Northrup defect formation energy. Using density functional theory, we calculate the energy of the defect, a Zn atom on a Ga site, using a supercell approach. The chemical potentials of Zn and Ga in the liquid catalyst particle are calculated from a thermodynamically assessed database including Au, Zn, Ga, and As. These quantities together with the chemical potential of the carriers enable us to calculate the hole concentration in the nanowires self-consistently. We validate our theoretical results against aerotaxy grown GaAs nanowires where we have varied the hole concentration by varying the Zn/Ga ratio in the aerotaxy growth. Full article

(This article belongs to the Special Issue Preparation and Application of Nanowires)

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10 pages, 1587 KiB

Open AccessArticle

Heat Dissipation in Flexible Nitride Nanowire Light-Emitting Diodes

by Nan Guan, Nuño Amador-Mendez, Arup Kunti, Andrey Babichev, Subrata Das, Akanksha Kapoor, Noëlle Gogneau, Joël Eymery, François Henri Julien, Christophe Durand and Maria Tchernycheva

Nanomaterials 2020, 10(11), 2271; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10112271 - 16 Nov 2020

Cited by 4 | Viewed by 2678

Abstract

We analyze the thermal behavior of a flexible nanowire (NW) light-emitting diode (LED) operated under different injection conditions. The LED is based on metal–organic vapor-phase deposition (MOCVD)-grown self-assembled InGaN/GaN NWs in a polydimethylsiloxane (PDMS) matrix. Despite the poor thermal conductivity of the polymer, [...] Read more.

We analyze the thermal behavior of a flexible nanowire (NW) light-emitting diode (LED) operated under different injection conditions. The LED is based on metal–organic vapor-phase deposition (MOCVD)-grown self-assembled InGaN/GaN NWs in a polydimethylsiloxane (PDMS) matrix. Despite the poor thermal conductivity of the polymer, active nitride NWs effectively dissipate heat to the substrate. Therefore, the flexible LED mounted on a copper heat sink can operate under high injection without significant overheating, while the device mounted on a plastic holder showed a 25% higher temperature for the same injected current. The efficiency of the heat dissipation by nitride NWs was further confirmed with finite-element modeling of the temperature distribution in a NW/polymer composite membrane. Full article

(This article belongs to the Special Issue Preparation and Application of Nanowires)

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15 pages, 19931 KiB

Open AccessArticle

Structural and Optical Properties of Self-Catalyzed Axially Heterostructured GaPN/GaP Nanowires Embedded into a Flexible Silicone Membrane

by Olga Yu. Koval, Vladimir V. Fedorov, Alexey D. Bolshakov, Sergey V. Fedina, Fedor M. Kochetkov, Vladimir Neplokh, Georgiy A. Sapunov, Liliia N. Dvoretckaia, Demid A. Kirilenko, Igor V. Shtrom, Regina M. Islamova, George E. Cirlin, Maria Tchernycheva, Alexey Yu. Serov and Ivan S. Mukhin

Nanomaterials 2020, 10(11), 2110; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10112110 - 23 Oct 2020

Cited by 19 | Viewed by 2633

Abstract

Controlled growth of heterostructured nanowires and mechanisms of their formation have been actively studied during the last decades due to perspectives of their implementation. Here, we report on the self-catalyzed growth of axially heterostructured GaPN/GaP nanowires on Si(111) by plasma-assisted molecular beam epitaxy. [...] Read more.

Controlled growth of heterostructured nanowires and mechanisms of their formation have been actively studied during the last decades due to perspectives of their implementation. Here, we report on the self-catalyzed growth of axially heterostructured GaPN/GaP nanowires on Si(111) by plasma-assisted molecular beam epitaxy. Nanowire composition and structural properties were examined by means of Raman microspectroscopy and transmission electron microscopy. To study the optical properties of the synthesized nanoheterostructures, the nanowire array was embedded into the silicone rubber membrane and further released from the growth substrate. The reported approach allows us to study the nanowire optical properties avoiding the response from the parasitically grown island layer. Photoluminescence and Raman studies reveal different nitrogen content in nanowires and parasitic island layer. The effect is discussed in terms of the difference in vapor solid and vapor liquid solid growth mechanisms. Photoluminescence studies at low temperature (5K) demonstrate the transition to the quasi-direct gap in the nanowires typical for diluted nitrides with low N-content. The bright room temperature photoluminescent response demonstrates the potential application of nanowire/polymer matrix in flexible optoelectronic devices. Full article

(This article belongs to the Special Issue Preparation and Application of Nanowires)

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