New Advances in Nanowires and Quantum Dots

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Synthesis, Interfaces and Nanostructures".

Deadline for manuscript submissions: closed (31 August 2023) | Viewed by 3082

Special Issue Editors


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Guest Editor
Department of Physics, Alferov University, Khlopina 8/3, 194021 St. Petersburg, Russia
Interests: molecular beam epitaxy; quantum dots; nanowires; semiconductor lasers; nanostructured devices
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Guest Editor
1. Faculty of Physics, St. Petersburg State University, Universitetskaya Emb. 13B, 199034 St. Petersburg, Russia
2. Russian Academy of Sciences, Ioffe Institute, Polytechnicheskaya 26, 194021 St. Petersburg, Russia
Interests: modeling, synthesis, and properties of semiconductor nanowires; semiconductor nanostructures; nucleation theory with applications
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Nanostructured materials such as quantum dots (zero-dimensional objects) and nanowires (exhibiting in extreme cases one-dimensional quantum behavior) attract great attention due to their intrinsic properties. A combination of one-dimensional and zero-dimensional semiconductor nanostructures may open new horizons in solid state physics and in various applications. In the frame of this Special Issue, different topics will be highlighted. For quantum dots, papers on the Stranski–Krastanow growth mechanism as well as droplet epitaxy fabrication methods are welcomed. Nanowires of different semiconductor materials grown by both top–down and bottom–up approaches will form a significant part of the issue. New types of the hybrid structures such as “quantum dot-in-a-nanowire” or “quantum well-in-a-nanowire” will also be covered. Finally, we will consider the recent progress in fabrication and properties of the so-called “crystal phase quantum dots”, where the charge confinement is defined by a crystal phase change in chemically homogeneous nanowire.

Dr. George Cirlin
Prof. Dr. Vladimir G. Dubrovskii
Guest Editors

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Keywords

  • quantum dots
  • nanowires
  • epitaxy
  • hybrid structures
  • crystal phase

Published Papers (3 papers)

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Research

12 pages, 2663 KiB  
Article
Can Nanowires Coalesce?
by Vladimir G. Dubrovskii
Nanomaterials 2023, 13(20), 2768; https://doi.org/10.3390/nano13202768 - 16 Oct 2023
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Abstract
Coalescence of nanowires and other three-dimensional structures into continuous film is desirable for growing low-dislocation-density III-nitride and III-V materials on lattice-mismatched substrates; this is also interesting from a fundamental viewpoint. Here, we develop a growth model for vertical nanowires which, under rather general [...] Read more.
Coalescence of nanowires and other three-dimensional structures into continuous film is desirable for growing low-dislocation-density III-nitride and III-V materials on lattice-mismatched substrates; this is also interesting from a fundamental viewpoint. Here, we develop a growth model for vertical nanowires which, under rather general assumptions on the solid-like coalescence process within the Kolmogorov crystallization theory, results in a morphological diagram for the asymptotic coverage of a substrate surface. The coverage is presented as a function of two variables: the material collection efficiency on the top nanowire facet a and the normalized surface diffusion flux of adatoms from the NW sidewalls b. The full coalescence of nanowires is possible only when a=1, regardless of b. At a>1, which often holds for vapor–liquid–solid growth with a catalyst droplet, nanowires can only partly merge but never coalesce into continuous film. In vapor phase epitaxy techniques, the NWs can partly merge but never fully coalesce, while in the directional molecular beam epitaxy the NWs can fully coalesce for small enough contact angles of their droplets corresponding to a=1. The growth kinetics of nanowires and evolution of the coverage in the pre-coalescence stage is also considered. These results can be used for predicting and controlling the degree of surface coverage by nanowires and three-dimensional islands by tuning the surface density, droplet size, adatoms diffusivity, and geometry of the initial structures in the vapor–liquid–solid, selective area, or self-induced growth by different epitaxy techniques. Full article
(This article belongs to the Special Issue New Advances in Nanowires and Quantum Dots)
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11 pages, 4405 KiB  
Article
Geometrical Selection of GaN Nanowires Grown by Plasma-Assisted MBE on Polycrystalline ZrN Layers
by Karol Olszewski, Marta Sobanska, Vladimir G. Dubrovskii, Egor D. Leshchenko, Aleksandra Wierzbicka and Zbigniew R. Zytkiewicz
Nanomaterials 2023, 13(18), 2587; https://doi.org/10.3390/nano13182587 - 19 Sep 2023
Viewed by 922
Abstract
GaN nanowires grown on metal substrates have attracted increasing interest for a wide range of applications. Herein, we report GaN nanowires grown by plasma-assisted molecular beam epitaxy on thin polycrystalline ZrN buffer layers, sputtered onto Si(111) substrates. The nanowire orientation was studied by [...] Read more.
GaN nanowires grown on metal substrates have attracted increasing interest for a wide range of applications. Herein, we report GaN nanowires grown by plasma-assisted molecular beam epitaxy on thin polycrystalline ZrN buffer layers, sputtered onto Si(111) substrates. The nanowire orientation was studied by X-ray diffraction and scanning electron microscopy, and then described within a model as a function of the Ga beam angle, nanowire tilt angle, and substrate rotation. We show that vertically aligned nanowires grow faster than inclined nanowires, which leads to an interesting effect of geometrical selection of the nanowire orientation in the directional molecular beam epitaxy technique. After a given growth time, this effect depends on the nanowire surface density. At low density, the nanowires continue to grow with random orientations as nucleated. At high density, the effect of preferential growth induced by the unidirectional supply of the material in MBE starts to dominate. Faster growing nanowires with smaller tilt angles shadow more inclined nanowires that grow slower. This helps to obtain more regular ensembles of vertically oriented GaN nanowires despite their random position induced by the metallic grains at nucleation. The obtained dense ensembles of vertically aligned GaN nanowires on ZrN/Si(111) surfaces are highly relevant for device applications. Importantly, our results are not specific for GaN nanowires on ZrN buffers, and should be relevant for any nanowires that are epitaxially linked to the randomly oriented surface grains in the directional molecular beam epitaxy. Full article
(This article belongs to the Special Issue New Advances in Nanowires and Quantum Dots)
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11 pages, 3236 KiB  
Article
Synthesis under Normal Conditions and Morphology and Composition of AlF3 Nanowires
by Albert Dautov, Kotstantin Kotlyar, Denis Butusov, Ivan Novikov, Aliya Khafizova and Artur Karimov
Nanomaterials 2023, 13(17), 2413; https://doi.org/10.3390/nano13172413 - 25 Aug 2023
Viewed by 1042
Abstract
AlF3 has interesting electrophysical properties, due to which the material is promising for applications in supercapacitors, UV coatings with low refractive index, excimer laser mirrors, and photolithography. The formation of AlF3-based nano- and micro-wires can bring new functionalities to AlF [...] Read more.
AlF3 has interesting electrophysical properties, due to which the material is promising for applications in supercapacitors, UV coatings with low refractive index, excimer laser mirrors, and photolithography. The formation of AlF3-based nano- and micro-wires can bring new functionalities to AlF3 material. AlF3 nanowires are used, for example, in functionally modified microprobes for a scanning probe microscope. In this work, we investigate the AlF3 samples obtained by the reaction of initial aluminum with an aqueous hydrofluoric acid solution of different concentrations. The peculiarity of our work is that the presented method for the synthesis of AlF3 and one-dimensional structures based on AlF3 is simple to perform and does not require any additional precursors or costs related to the additional source materials. All the samples were obtained under normal conditions. The morphology of the nanowire samples is studied using scanning electron microscopy. We performed an intermediate atomic force microscope analysis of dissolved Al samples to analyze the reactions occurring on the metal surface. The surface of the obtained samples was analyzed using a scanning electron microscope. During the analysis, it was found that under the given conditions, whiskers were synthesized. The scale of one-dimensional structures varies depending on the given parameters in the system. Quantitative energy-dispersive x-ray spectroscopy spectra are obtained and analyzed with respect to the feedstock and each other. Full article
(This article belongs to the Special Issue New Advances in Nanowires and Quantum Dots)
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