Research

15 pages, 6817 KiB

Open AccessEditor’s ChoiceArticle

Solution-Mediated Inversion of SnSe to Sb₂Se₃ Thin-Films

by Svetlana Polivtseva, Julia Kois, Tatiana Kruzhilina, Reelika Kaupmees, Mihhail Klopov, Palanivel Molaiyan, Heleen van Gog, Marijn A. van Huis and Olga Volobujeva

Nanomaterials 2022, 12(17), 2898; https://doi.org/10.3390/nano12172898 - 23 Aug 2022

Viewed by 1799

Abstract

New facile and controllable approaches to fabricating metal chalcogenide thin films with adjustable properties can significantly expand the scope of these materials in numerous optoelectronic and photovoltaic devices. Most traditional and especially wet-chemical synthetic pathways suffer from a sluggish ability to regulate the [...] Read more.

New facile and controllable approaches to fabricating metal chalcogenide thin films with adjustable properties can significantly expand the scope of these materials in numerous optoelectronic and photovoltaic devices. Most traditional and especially wet-chemical synthetic pathways suffer from a sluggish ability to regulate the composition and have difficulty achieving the high-quality structural properties of the sought-after metal chalcogenides, especially at large 2D length scales. In this effort, and for the first time, we illustrated the fast and complete inversion of continuous SnSe thin-films to Sb₂Se₃ using a scalable top-down ion-exchange approach. Processing in dense solution systems yielded the formation of Sb₂Se₃ films with favorable structural characteristics, while oxide phases, which are typically present in most Sb₂Se₃ films regardless of the synthetic protocols used, were eliminated. Density functional theory (DFT) calculations performed on intermediate phases show strong relaxations of the atomic lattice due to the presence of substitutional and vacancy defects, which likely enhances the mobility of cationic species during cation exchange. Our concept can be applied to customize the properties of other metal chalcogenides or manufacture layered structures. Full article

(This article belongs to the Special Issue Nanowires and Quantum Dots)

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9 pages, 1790 KiB

Open AccessArticle

Temperature-Dependent Exciton Dynamics in a Single GaAs Quantum Ring and a Quantum Dot

by Heedae Kim, Jong Su Kim and Jin Dong Song

Nanomaterials 2022, 12(14), 2331; https://doi.org/10.3390/nano12142331 - 07 Jul 2022

Cited by 1 | Viewed by 1336

Abstract

Micro-photoluminescence was observed while increasing the excitation power in a single GaAs quantum ring (QR) at 4 K. Fine structures at the energy levels of the ground (N = 1) and excited (N = 2) state excitons exhibited a blue shift [...] Read more.

Micro-photoluminescence was observed while increasing the excitation power in a single GaAs quantum ring (QR) at 4 K. Fine structures at the energy levels of the ground (N = 1) and excited (N = 2) state excitons exhibited a blue shift when excitation power increased. The excited state exciton had a strong polarization dependence that stemmed from the asymmetric localized state. According to temperature-dependence measurements, strong exciton–phonon interaction (48 meV) was observed from an excited exciton state in comparison with the weak exciton–phonon interaction (27 meV) from the ground exciton state, resulting from enhanced confinement in the excited exciton state. In addition, higher activation energy (by 20 meV) was observed for the confined electrons in a single GaAs QR, where the confinement effect was enhanced by the asymmetric ring structure. Full article

(This article belongs to the Special Issue Nanowires and Quantum Dots)

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14 pages, 5644 KiB

Open AccessArticle

Measuring Non-Destructively the Total Indium Content and Its Lateral Distribution in Very Thin Single Layers or Quantum Dots Deposited onto Gallium Arsenide Substrates Using Energy-Dispersive X-ray Spectroscopy in a Scanning Electron Microscope

by Thomas Walther

Nanomaterials 2022, 12(13), 2220; https://doi.org/10.3390/nano12132220 - 28 Jun 2022

Cited by 2 | Viewed by 1709

Abstract

The epitaxial deposition of a precise number, or even fractions, of monolayers of indium (In)-rich semiconductors onto gallium arsenide (GaAs) substrates enables the creation of quantum dots based on InAs, InGaAs and indium phosphide (InP) for infrared light-emitting and laser diodes and the [...] Read more.

The epitaxial deposition of a precise number, or even fractions, of monolayers of indium (In)-rich semiconductors onto gallium arsenide (GaAs) substrates enables the creation of quantum dots based on InAs, InGaAs and indium phosphide (InP) for infrared light-emitting and laser diodes and the formation of indium antimonide (InSb)/GaAs strained layer superlattices. Here, a facile method based on energy-dispersive X-ray spectroscopy (EDXS) in a scanning electron microscope (SEM) is presented that allows the indium content of a single semiconductor layer deposited on a gallium arsenide substrate to be measured with relatively high accuracy (±0.7 monolayers). As the procedure works in top-down geometry, where any part of a wafer can be inspected, measuring the In content of the surface layer in one location without destroying it can also be used to map the lateral indium distribution during quantum dot formation and is a method suitable as an in-situ quality control tool for epitaxy. Full article

(This article belongs to the Special Issue Nanowires and Quantum Dots)

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9 pages, 3002 KiB

Open AccessArticle

Understanding the Morphological Evolution of InSb Nanoflags Synthesized in Regular Arrays by Chemical Beam Epitaxy

by Isha Verma, Valentina Zannier, Vladimir G. Dubrovskii, Fabio Beltram and Lucia Sorba

Nanomaterials 2022, 12(7), 1090; https://doi.org/10.3390/nano12071090 - 26 Mar 2022

Viewed by 1361

Abstract

InSb nanoflags are grown by chemical beam epitaxy in regular arrays on top of Au-catalyzed InP nanowires synthesized on patterned SiO₂/InP(111)B substrates. Two-dimensional geometry of the nanoflags is achieved by stopping the substrate rotation in the step of the InSb growth. [...] Read more.

InSb nanoflags are grown by chemical beam epitaxy in regular arrays on top of Au-catalyzed InP nanowires synthesized on patterned SiO₂/InP(111)B substrates. Two-dimensional geometry of the nanoflags is achieved by stopping the substrate rotation in the step of the InSb growth. Evolution of the nanoflag length, thickness and width with the growth time is studied for different pitches (distances in one of the two directions of the substrate plane). A model is presented which explains the observed non-linear time dependence of the nanoflag length, saturation of their thickness and gradual increase in the width by the shadowing effect for re-emitted Sb flux. These results might be useful for morphological control of InSb and other III-V nanoflags grown in regular arrays. Full article

(This article belongs to the Special Issue Nanowires and Quantum Dots)

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13 pages, 1755 KiB

Open AccessArticle

Theory of MBE Growth of Nanowires on Adsorbing Substrates: The Role of the Shadowing Effect on the Diffusion Transport

by Vladimir G. Dubrovskii

Nanomaterials 2022, 12(7), 1064; https://doi.org/10.3390/nano12071064 - 24 Mar 2022

Cited by 5 | Viewed by 1783

Abstract

A new model for nanowire growth by molecular beam epitaxy is proposed which extends the earlier approaches treating an isolated nanowire to the case of ensembles of nanowires. I consider an adsorbing substrate on which the arriving growth species (group III adatoms for [...] Read more.

A new model for nanowire growth by molecular beam epitaxy is proposed which extends the earlier approaches treating an isolated nanowire to the case of ensembles of nanowires. I consider an adsorbing substrate on which the arriving growth species (group III adatoms for III-V nanowires) may diffuse to the nanowire base and subsequently to the top without desorption. Analytical solution for the nanowire length evolution at a constant radius shows that the shadowing of the substrate surface is efficient and affects the growth kinetics from the very beginning of growth in dense enough ensembles of nanowires. The model fits quite well the kinetic data on different Au-catalyzed and self-catalyzed III-V nanowires. This approach should work equally well for vapor-liquid-solid and catalyst-free nanowires grown by molecular beam epitaxy and related deposition techniques on unpatterned or masked substrates. Full article

(This article belongs to the Special Issue Nanowires and Quantum Dots)

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14 pages, 2391 KiB

Open AccessFeature PaperArticle

Theory of MBE Growth of Nanowires on Reflecting Substrates

by Vladimir G. Dubrovskii

Nanomaterials 2022, 12(2), 253; https://doi.org/10.3390/nano12020253 - 14 Jan 2022

Cited by 10 | Viewed by 1632

Abstract

Selective area growth (SAG) of III-V nanowires (NWs) by molecular beam epitaxy (MBE) and related epitaxy techniques offer several advantages over growth on unpatterned substrates. Here, an analytic model for the total flux of group III atoms impinging NWs is presented, which accounts [...] Read more.

Selective area growth (SAG) of III-V nanowires (NWs) by molecular beam epitaxy (MBE) and related epitaxy techniques offer several advantages over growth on unpatterned substrates. Here, an analytic model for the total flux of group III atoms impinging NWs is presented, which accounts for specular re-emission from the mask surface and the shadowing effect in the absence of surface diffusion from the substrate. An expression is given for the shadowing length of NWs corresponding to the full shadowing of the mask. Axial and radial NW growths are considered in different stages, including the stage of purely axial growth, intermediate stage with radial growth, and asymptotic stage, where the NWs receive the maximum flux determined by the array pitch. The model provides good fits with the data obtained for different vapor–liquid–solid and catalyst-free III-V NWs. Full article

(This article belongs to the Special Issue Nanowires and Quantum Dots)

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9 pages, 1262 KiB

Open AccessArticle

Purcell Effect and Beaming of Emission in Hybrid AlGaAs Nanowires with GaAs Quantum Dots

by Rodion R. Reznik, George E. Cirlin, Konstantin P. Kotlyar, Igor V. Ilkiv, Nika Akopian, Lorenzo Leandro, Valentin V. Nikolaev, Alexey V. Belonovski and Mikhail A. Kaliteevski

Nanomaterials 2021, 11(11), 2894; https://doi.org/10.3390/nano11112894 - 29 Oct 2021

Cited by 2 | Viewed by 1691

Abstract

Control of directionality of emissions is an important task for the realization of novel nanophotonic devices based on nanowires. Most of the existing approaches providing high directionality of the light emitted from nanowires are based on the utilization of the tapered shape of [...] Read more.

Control of directionality of emissions is an important task for the realization of novel nanophotonic devices based on nanowires. Most of the existing approaches providing high directionality of the light emitted from nanowires are based on the utilization of the tapered shape of nanowires, serving as nanoantenna coupling with the light waveguided in nanowire and the directional output beam. Here we report the beaming of the emitted light with wavelength near 800 nm by naturally formed core-shell AlGaAs NW with multiply GaAs quantum dots (QDs) diameter 30 nm and height 10 nm, while the diameter of NW 130 nm, what does not support efficient emission into waveguided modes, including the mode HE₁₁. Experimental measurements show that intensity of emission for directions in the vicinity of the axis of NW is about two orders of magnitude higher than for perpendicular directions. The developed theoretical approach allowed us to calculate the probability of spontaneous emission for various directions and into waveguided modes and showed that highly directional radiation can be provided by the intrinsic emission properties of cylindrical NW. Our results suggest that for the small diameter of NW, directional emissions are associated with an TM₀ leaky mode (when electric field oriented in axial direction) and therefore manifests in an existence of axial electric dipole transitions in quantum dots. Full article

(This article belongs to the Special Issue Nanowires and Quantum Dots)

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9 pages, 1373 KiB

Open AccessArticle

Influence of TOPO and TOPO-CdSe/ZnS Quantum Dots on Luminescence Photodynamics of InP/InAsP/InPHeterostructure Nanowires

by Artem I. Khrebtov, Vladimir V. Danilov, Anastasia S. Kulagina, Rodion R. Reznik, Ivan D. Skurlov, Alexander P. Litvin, Farrukh M. Safin, Vladislav O. Gridchin, Dmitriy S. Shevchuk, Stanislav V. Shmakov, Artem N. Yablonskiy and George E. Cirlin

Nanomaterials 2021, 11(3), 640; https://doi.org/10.3390/nano11030640 - 05 Mar 2021

Cited by 5 | Viewed by 2240

Abstract

The passivation influence by ligands coverage with trioctylphosphine oxide (TOPO) and TOPO including colloidal CdSe/ZnS quantum dots (QDs) on optical properties of the semiconductor heterostructure, namely an array of InP nanowires (NWs) with InAsP nanoinsertion grown by Au-assisted molecular beam epitaxy on Si [...] Read more.

The passivation influence by ligands coverage with trioctylphosphine oxide (TOPO) and TOPO including colloidal CdSe/ZnS quantum dots (QDs) on optical properties of the semiconductor heterostructure, namely an array of InP nanowires (NWs) with InAsP nanoinsertion grown by Au-assisted molecular beam epitaxy on Si (111) substrates, was investigated. A significant dependence of the photoluminescence (PL) dynamics of the InAsP insertions on the ligand type was shown, which was associated with the changes in the excitation translation channels in the heterostructure. This change was caused by a different interaction of the ligand shells with the surface of InP NWs, which led to the formation of different interfacial low-energy states at the NW-ligand boundary, such as surface-localized antibonding orbitals and hybridized states that were energetically close to the radiating state and participate in the transfer of excitation. It was shown that the quenching of excited states associated with the capture of excitation to interfacial low-energy traps was compensated by the increasing role of the “reverse transfer” mechanism. As a result, the effectiveness of TOPO-CdSe/ZnS QDs as a novel surface passivation coating was demonstrated. Full article

(This article belongs to the Special Issue Nanowires and Quantum Dots)

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