Research

13 pages, 3120 KiB

Open AccessArticle

Photoluminescence Redistribution of InGaN Nanowires Induced by Plasmonic Silver Nanoparticles

by Talgat Shugabaev, Vladislav O. Gridchin, Sergey D. Komarov, Demid A. Kirilenko, Natalia V. Kryzhanovskaya, Konstantin P. Kotlyar, Rodion R. Reznik, Yelizaveta I. Girshova, Valentin V. Nikolaev, Michael A. Kaliteevski and George E. Cirlin

Nanomaterials 2023, 13(6), 1069; https://doi.org/10.3390/nano13061069 - 16 Mar 2023

Cited by 3 | Viewed by 1456

Abstract

Hybrid nanostructures based on InGaN nanowires with decorated plasmonic silver nanoparticles are investigated in the present study. It is shown that plasmonic nanoparticles induce the redistribution of room temperature photoluminescence between short-wavelength and long-wavelength peaks of InGaN nanowires. It is defined that short-wavelength [...] Read more.

Hybrid nanostructures based on InGaN nanowires with decorated plasmonic silver nanoparticles are investigated in the present study. It is shown that plasmonic nanoparticles induce the redistribution of room temperature photoluminescence between short-wavelength and long-wavelength peaks of InGaN nanowires. It is defined that short-wavelength maxima decreased by 20%, whereas the long-wavelength maxima increased by 19%. We attribute this phenomenon to the energy transfer and enhancement between the coalesced part of the NWs with 10–13% In content and the tips above with an In content of about 20–23%. A proposed Fröhlich resonance model for silver NPs surrounded by a medium with refractive index of 2.45 and spread 0.1 explains the enhancement effect, whereas the decreasing of the short-wavelength peak is associated with the diffusion of charge carriers between the coalesced part of the NWs and the tips above. Full article

(This article belongs to the Special Issue One-Dimensional Nanostructures: Synthesis, Characterization and Applications)

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16 pages, 14850 KiB

Open AccessArticle

Tuning the Liquid–Vapour Interface of VLS Epitaxy for Creating Novel Semiconductor Nanostructures

by Galih R. Suwito, Vladimir G. Dubrovskii, Zixiao Zhang, Weizhen Wang, Sofiane Haffouz, Dan Dalacu, Philip J. Poole, Peter Grutter and Nathaniel J. Quitoriano

Nanomaterials 2023, 13(5), 894; https://doi.org/10.3390/nano13050894 - 27 Feb 2023

Viewed by 1190

Abstract

Controlling the morphology and composition of semiconductor nano- and micro-structures is crucial for fundamental studies and applications. Here, Si-Ge semiconductor nanostructures were fabricated using photolithographically defined micro-crucibles on Si substrates. Interestingly, the nanostructure morphology and composition of these structures are strongly dependent on [...] Read more.

Controlling the morphology and composition of semiconductor nano- and micro-structures is crucial for fundamental studies and applications. Here, Si-Ge semiconductor nanostructures were fabricated using photolithographically defined micro-crucibles on Si substrates. Interestingly, the nanostructure morphology and composition of these structures are strongly dependent on the size of the liquid–vapour interface (i.e., the opening of the micro-crucible) in the CVD deposition step of Ge. In particular, Ge crystallites nucleate in micro-crucibles with larger opening sizes (3.74–4.73 μm²), while no such crystallites are found in micro-crucibles with smaller openings of 1.15 μm². This interface area tuning also results in the formation of unique semiconductor nanostructures: lateral nano-trees (for smaller openings) and nano-rods (for larger openings). Further TEM imaging reveals that these nanostructures have an epitaxial relationship with the underlying Si substrate. This geometrical dependence on the micro-scale vapour–liquid–solid (VLS) nucleation and growth is explained within a dedicated model, where the incubation time for the VLS Ge nucleation is inversely proportional to the opening size. The geometric effect on the VLS nucleation can be used for the fine tuning of the morphology and composition of different lateral nano- and micro-structures by simply changing the area of the liquid–vapour interface. Full article

(This article belongs to the Special Issue One-Dimensional Nanostructures: Synthesis, Characterization and Applications)

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12 pages, 7693 KiB

Open AccessEditor’s ChoiceArticle

Transverse Magnetic Surface Plasmons in Graphene Nanoribbon Qubits: The Influence of a VO₂ Substrate

by Mousa Bahrami and Panagiotis Vasilopoulos

Nanomaterials 2023, 13(4), 718; https://doi.org/10.3390/nano13040718 - 13 Feb 2023

Viewed by 1682

Abstract

We study the influence of the phase-change material VO₂ on transverse magnetic (TM) surface plasmon (SP) modes in metallic arm-chair graphene nanoribbon (AGNR) qubits in the Lindhard approximation. We assess the effects of temperature as a dynamic knob for the transition from [...] Read more.

We study the influence of the phase-change material VO₂ on transverse magnetic (TM) surface plasmon (SP) modes in metallic arm-chair graphene nanoribbon (AGNR) qubits in the Lindhard approximation. We assess the effects of temperature as a dynamic knob for the transition from the insulating to the metallic phase on the TM SP modes in single-band (SB) and two-band (TB) transitions. We show that a VO₂ substrate leads to TM SP modes in both SB and TB transitions. In addition, we observe that the SP modes have a lower frequency than those for a substrate of constant permittivity. In addition, we study the influence of the substrate-induced band gap

Δ^{'}

on SP modes in TB transitions for the insulating and metallic phases of VO₂. Full article

(This article belongs to the Special Issue One-Dimensional Nanostructures: Synthesis, Characterization and Applications)

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13 pages, 3876 KiB

Open AccessArticle

Controllable Connection of Fe₂Se₃ Double Chains and Fe(dien)₂ Complexes for Organic–Inorganic Hybrid Ferrimagnet with a Large Coercivity

by Xiaolei Shang, Xiaoling Men, Qifeng Kuang, Shaojie Li, Da Li and Zhidong Zhang

Nanomaterials 2023, 13(3), 487; https://doi.org/10.3390/nano13030487 - 25 Jan 2023

Cited by 1 | Viewed by 1231

Abstract

Organic–inorganic hybrid materials built by inorganic and organic building units have attracted intensive interest in the past decades due to unique chemical and physical properties. However, rare organic–inorganic hybrid materials show excellent permanent magnetic properties. Here, we develop a facile chemical solution method [...] Read more.

Organic–inorganic hybrid materials built by inorganic and organic building units have attracted intensive interest in the past decades due to unique chemical and physical properties. However, rare organic–inorganic hybrid materials show excellent permanent magnetic properties. Here, we develop a facile chemical solution method to bottom-up synthesize a new hybrid (Fe₂Se₃)₂[Fe(dien)₂]_0.9. This hybrid phase with the space group P2₁/c (14) possesses a rodlike shape with a diameter of 100–2000 nm and a length of 5–50 µm. The hybrid rods are ferrimagnetic with a Curie temperature (T_C) of 11 K. They show a high coercivity (H_C) of 4.67 kOe and a saturation magnetization (M_S) of 13.5 emu/g at 2 K. Compared with orthorhombic (FeSe₂)₂Fe(dien)₂, the excellent magnetic performance of the hybrid rods is ascribed to the monoclinic hybrid structure built by Fe(dien)₂ complexes and Fe₂Se₃ double chains. Our study provides guidance for connecting inorganic fragments of FeSe₂ single chains, Fe₂Se₃ double chains or β-Fe₃Se₄ layers with Fe(dien)₂ complexes for organic–inorganic hybrid phases with varied crystal structures and magnetic properties. Full article

(This article belongs to the Special Issue One-Dimensional Nanostructures: Synthesis, Characterization and Applications)

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13 pages, 531 KiB

Open AccessArticle

Totally Spin-Polarized Currents in an Interferometer with Spin–Orbit Coupling and the Absence of Magnetic Field Effects

by Victor Lopes, Guillermo Chiappe, Laercio C. Ribeiro and Enrique V. Anda

Nanomaterials 2022, 12(22), 4082; https://doi.org/10.3390/nano12224082 - 20 Nov 2022

Viewed by 1367

Abstract

The paper studies the electronic current in a one-dimensional lead under the effect of spin–orbit coupling and its injection into a metallic conductor through two contacts, forming a closed loop. When an external potential is applied, the time reversal symmetry is broken and [...] Read more.

The paper studies the electronic current in a one-dimensional lead under the effect of spin–orbit coupling and its injection into a metallic conductor through two contacts, forming a closed loop. When an external potential is applied, the time reversal symmetry is broken and the wave vector k of the circulating electrons that contribute to the current is spin-dependent. As the wave function phase depends upon the vector k, the closed path in the circuit produces spin-dependent current interference. This creates a physical scenario in which a spin-polarized current emerges, even in the absence of external magnetic fields or magnetic materials. It is possible to find points in the system’s parameter space and, depending upon its geometry, the value of the Fermi energy and the spin–orbit intensities, for which the electronic states participating in the current have only one spin, creating a high and totally spin-polarized conductance. For a potential of a few tens of meV, it is possible to obtain a spin-polarized current of the order of

μ

A. The properties of the obtained electronic current qualify the proposed device as a potentially important tool for spintronics applications. Full article

(This article belongs to the Special Issue One-Dimensional Nanostructures: Synthesis, Characterization and Applications)

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13 pages, 3519 KiB

Open AccessArticle

Criterion for Selective Area Growth of III-V Nanowires

by Vladimir G. Dubrovskii

Nanomaterials 2022, 12(20), 3698; https://doi.org/10.3390/nano12203698 - 21 Oct 2022

Cited by 1 | Viewed by 1276

Abstract

A model for the nucleation of vertical or planar III-V nanowires (NWs) in selective area growth (SAG) on masked substrates with regular arrays of openings is developed. The optimal SAG zone, with NW nucleation within the openings and the absence of parasitic III-V [...] Read more.

A model for the nucleation of vertical or planar III-V nanowires (NWs) in selective area growth (SAG) on masked substrates with regular arrays of openings is developed. The optimal SAG zone, with NW nucleation within the openings and the absence of parasitic III-V crystallites or group III droplets on the mask, is established, taking into account the minimum chemical potential of the III-V pairs required for nucleation on different surfaces, and the surface diffusion of the group III adatoms. The SAG maps are plotted in terms of the material fluxes versus the temperature. The non-trivial behavior of the SAG window, with the opening size and pitch, is analyzed, depending on the direction of the diffusion flux of the group III adatoms into or from the openings. A good correlation of the model with the data on the SAG of vertical GaN NWs and planar GaAs and InAs NWs by molecular beam epitaxy (MBE) is demonstrated. Full article

(This article belongs to the Special Issue One-Dimensional Nanostructures: Synthesis, Characterization and Applications)

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13 pages, 2208 KiB

Open AccessEditor’s ChoiceArticle

Elucidation of Strain-Dependent, Zinc Oxide Nanorod Response for Nanorod-Guided Fluorescence Intensity

by Johnson Truong, Andrew Stoner, Marion Ryan C. Sytu, T Rizana Tatlock, David H. Cho and Jong-in Hahm

Nanomaterials 2022, 12(20), 3558; https://doi.org/10.3390/nano12203558 - 11 Oct 2022

Cited by 1 | Viewed by 1193

Abstract

In this work, we examine how strain exerted on individual ZnO nanorods (NRs) can influence the fluorescence signals that are emitted from fluorophore molecules and subsequently coupled into and guided along the NR. We elucidate the relationships between the incremental levels of compressive [...] Read more.

In this work, we examine how strain exerted on individual ZnO nanorods (NRs) can influence the fluorescence signals that are emitted from fluorophore molecules and subsequently coupled into and guided along the NR. We elucidate the relationships between the incremental levels of compressive and tensile strain on the NRs and measured fluorescence intensity of a model fluorophore, rhodamine 6G (R6G), as a function of the position on the NRs. We reveal that compressive strain on the NRs leads to a decrease in the guided fluorescence signal, while tensile strain leads to an increase in the fluorescence intensity. Compared to an unstrained state, approximately 35% decrease (increase) in R6G fluorescence intensity was observed from ZnO NRs when they were under compressive strain of −14% (tensile strain of +10%). Further, our systematic acquisition of the incremental addition of uniaxial strain result in a linear relationship of the coupled fluorescence signal and the amount of applied strain. The degree of fluorescence intensification on nanorod ends (DoF), which is a quantitative indicator for the amount of R6G signals coupled into and waveguided to the NR ends compared to those on the main body, also exhibits a linear relationship with strain. These outcomes, in turn, demonstrate that strain alters the waveguiding capabilities of ZnO NRs in a predictable manner, which can be exploited to modulate and optimize fluorescence and other light signals emitted by a nearby source. Considering the wide utility of ZnO NRs in photonics, optoelectronics, and sensors, insights from our study may be highly valuable to effectively controlling and enhancing optical signals from chemical and biological analytes through strain. Full article

(This article belongs to the Special Issue One-Dimensional Nanostructures: Synthesis, Characterization and Applications)

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13 pages, 2466 KiB

Open AccessArticle

Theory of MOCVD Growth of III-V Nanowires on Patterned Substrates

by Vladimir G. Dubrovskii

Nanomaterials 2022, 12(15), 2632; https://doi.org/10.3390/nano12152632 - 30 Jul 2022

Cited by 4 | Viewed by 1198

Abstract

An analytic model for III-V nanowire growth by metal organic chemical vapor deposition (MOCVD) in regular arrays on patterned substrates is presented. The model accounts for some new features that, to the author’s knowledge, have not yet been considered. It is shown that [...] Read more.

An analytic model for III-V nanowire growth by metal organic chemical vapor deposition (MOCVD) in regular arrays on patterned substrates is presented. The model accounts for some new features that, to the author’s knowledge, have not yet been considered. It is shown that MOCVD growth is influenced by an additional current into the nanowires originating from group III atoms reflected from an inert substrate and the upper limit for the group III current per nanowire given by the total group III flow and the array pitch. The model fits the data on the growth kinetics of Au-catalyzed and catalyst-free III-V nanowires quite well and should be useful for understanding and controlling the MOCVD nanowire growth in general. Full article

(This article belongs to the Special Issue One-Dimensional Nanostructures: Synthesis, Characterization and Applications)

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11 pages, 2442 KiB

Open AccessArticle

Modeling the Radial Growth of Self-Catalyzed III-V Nanowires

by Vladimir G. Dubrovskii and Egor D. Leshchenko

Nanomaterials 2022, 12(10), 1698; https://doi.org/10.3390/nano12101698 - 16 May 2022

Cited by 2 | Viewed by 1215

Abstract

A new model for the radial growth of self-catalyzed III-V nanowires on different substrates is presented, which describes the nanowire morphological evolution without any free parameters. The model takes into account the re-emission of group III atoms from a mask surface and the [...] Read more.

A new model for the radial growth of self-catalyzed III-V nanowires on different substrates is presented, which describes the nanowire morphological evolution without any free parameters. The model takes into account the re-emission of group III atoms from a mask surface and the shadowing effect in directional deposition techniques such as molecular beam epitaxy. It is shown that radial growth is faster for larger pitches of regular nanowire arrays or lower surface density, and can be suppressed by increasing the V/III flux ratio or decreasing re-emission. The model describes quite well the data on the morphological evolution of Ga-catalyzed GaP and GaAs nanowires on different substrates, where the nanowire length increases linearly and the radius enlarges sub-linearly with time. The obtained analytical expressions and numerical data should be useful for morphological control over different III-V nanowires in a wide range of growth conditions. Full article

(This article belongs to the Special Issue One-Dimensional Nanostructures: Synthesis, Characterization and Applications)

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15 pages, 2216 KiB

Open AccessEditor’s ChoiceArticle

Thermal Conductivity of GaAs Nanowire Arrays Measured by the 3ω Method

by Ara Ghukasyan, Pedro Oliveira, Nebile Isik Goktas and Ray LaPierre

Nanomaterials 2022, 12(8), 1288; https://doi.org/10.3390/nano12081288 - 10 Apr 2022

Cited by 4 | Viewed by 1999

Abstract

Vertical nanowire (NW) arrays are the basis for a variety of nanoscale devices. Understanding heat transport in these devices is an important concern, especially for prospective thermoelectric applications. To facilitate thermal conductivity measurements on as-grown NW arrays, a common NW-composite device architecture was [...] Read more.

Vertical nanowire (NW) arrays are the basis for a variety of nanoscale devices. Understanding heat transport in these devices is an important concern, especially for prospective thermoelectric applications. To facilitate thermal conductivity measurements on as-grown NW arrays, a common NW-composite device architecture was adapted for use with the 3ω method. We describe the application of this technique to obtain thermal conductivity measurements on two GaAs NW arrays featuring ~130 nm diameter NWs with a twinning superlattice (TSL) and a polytypic (zincblende/wurtzite) crystal structure, respectively. Our results indicate NW thermal conductivities of 5.2 ± 1.0 W/m-K and 8.4 ± 1.6 W/m-K in the two samples, respectively, showing a significant reduction in the former, which is the first such measurements on TSL NWs. Nearly an order of magnitude difference from the bulk thermal conductivity (~50 W/m-K) is observed for the TSL NW sample, one of the lowest values measured to date for GaAs NWs. Full article

(This article belongs to the Special Issue One-Dimensional Nanostructures: Synthesis, Characterization and Applications)

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