Special Issue "Novel Synthesis Strategies and Phenomena in Low-Dimensional Structures Like Nanowires and Thin Films"

A special issue of Nanomaterials (ISSN 2079-4991).

Deadline for manuscript submissions: closed (15 September 2019).

Special Issue Editor

Prof. Usha Philipose
E-Mail Website
Guest Editor
Department of Physics, University of North Texas, Denton, United States
Interests: The predicted limits to continued miniaturization of electronic devices have motivated intensive research efforts to develop novel strategies for synthesizing and characterizing nanoscale structures. Of special interest are one-dimensional (1D) nanostructures —nanowires. My research group works on the synthesis and characterization of semiconductor nanowires and nanocomposites. We are interested in understanding the fundamentals of electron, photon and phonon transport in 1D nanostructures and how size effects that cause strong confinement of carriers in these nanostructures can be exploited to engineer their intrinsic properties.
Research in my lab is geared towards increasing the complexity of the 1D structures by fabricating core-shell heterostructures, engineering surface roughness and creating well-defined heterojunctions along the length of the nanowires. We are interested in studying the effects of such complexities on certain functionalities such as its optoelectronic and energy conversion capabilities.

Special Issue Information

Dear Colleagues,

This Special Issue will cover topics highlighting advancements in low-dimensional material synthesis and characterization. The nanostructures could be one-dimensional structures like nanotubes/nanowires or atomically thin films of metal-dichacolgenides. Novel phenomena could include electronic effects like Coulomb blockade, single-electron tunneling or promising linear/non-linear optical and phonon-related effects. This Special Issue welcomes all submissions from studies dealing with novel synthesis and characterization strategies of 1D nanostructures, including heterostructures and nanocomposites. Research on the design of nanoscale devices based on new principles related to size effects are strongly encouraged.

Prof. Usha Philipose
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Nanomaterials is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • nanostructures
  • synthesis
  • novel phenomena
  • monolayers
  • metal tri-chalcogenides
  • nanowires
  • atomic thickness
  • thin films
  • semiconductors

Published Papers (10 papers)

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Research

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Open AccessArticle
Direct Growth of Two Dimensional Molybdenum Disulfide on Flexible Ceramic Substrate
Nanomaterials 2019, 9(10), 1456; https://doi.org/10.3390/nano9101456 - 14 Oct 2019
Abstract
In this paper, we report the first successful demonstration of the direct growth of high-quality two-dimensional (2D) MoS2 semiconductors on a flexible substrate using a 25-μm-thick Yttria-stabilized zirconia ceramic substrate. Few-layered MoS2 crystals grown at 800 °C showed a uniform crystal [...] Read more.
In this paper, we report the first successful demonstration of the direct growth of high-quality two-dimensional (2D) MoS2 semiconductors on a flexible substrate using a 25-μm-thick Yttria-stabilized zirconia ceramic substrate. Few-layered MoS2 crystals grown at 800 °C showed a uniform crystal size of approximately 50 μm, which consisted of about 10 MoS2 layers. MoS2 crystals were characterized using energy-dispersive X-ray spectroscopy. Raman spectroscopy was performed to investigate the crystal quality under bending conditions. The Raman mapping revealed a good uniformity with a stable chemical composition of the MoS2 crystals. Our approach offers a simple and effective route to realize various flexible electronics based on MoS2. Our approach can be applied for MoS2 growth and for other 2D materials. Therefore, it offers a new opportunity that allows us to demonstrate high-performance flexible electronic/optoelectronic applications in a less expensive, simpler, and faster manner without sacrificing the intrinsic performance of 2D materials. Full article
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Open AccessArticle
The Stability of Metallic MoS2 Nanosheets and Their Property Change by Annealing
Nanomaterials 2019, 9(10), 1366; https://doi.org/10.3390/nano9101366 - 24 Sep 2019
Abstract
Highly pure 1T MoS2 nanosheets were grown at 200 °C by a hydrothermal process. The effects of mild annealing on the structural and physical properties of the MoS2 were studied by heating the nanosheets in air and vacuum up to 350 [...] Read more.
Highly pure 1T MoS2 nanosheets were grown at 200 °C by a hydrothermal process. The effects of mild annealing on the structural and physical properties of the MoS2 were studied by heating the nanosheets in air and vacuum up to 350 °C. It was found that the annealing leads to an increase in resistivity for the nanosheets by 3 orders of magnitude, the appearance of two absorption bands in the visible range, and a hydrophilic to hydrophobic change in the surface wetting properties. Monitoring of the annealing process by Raman spectroscopy indicates that the material property changes are associated with a 1T to 2H MoS2 phase transition, with activation energies of 517 meV in air and 260 meV in vacuum. This study provides another way to control the electrical, optical, and surface properties of MoS2 nanosheets for fulfilling the needs of various applications. Full article
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Open AccessArticle
Strain-Mediated Bending of InP Nanowires through the Growth of an Asymmetric InAs Shell
Nanomaterials 2019, 9(9), 1327; https://doi.org/10.3390/nano9091327 - 16 Sep 2019
Abstract
Controlling nanomaterial shape beyond its basic dimensionality is a concurrent challenge tackled by several growth and processing avenues. One of these is strain engineering of nanowires, implemented through the growth of asymmetrical heterostructures. Here, we report metal–organic molecular beam epitaxy of bent InP/InAs [...] Read more.
Controlling nanomaterial shape beyond its basic dimensionality is a concurrent challenge tackled by several growth and processing avenues. One of these is strain engineering of nanowires, implemented through the growth of asymmetrical heterostructures. Here, we report metal–organic molecular beam epitaxy of bent InP/InAs core/shell nanowires brought by precursor flow directionality in the growth chamber. We observe the increase of bending with decreased core diameter. We further analyze the composition of a single nanowire and show through supporting finite element simulations that strain accommodation following the lattice mismatch between InP and InAs dominates nanowire bending. The simulations show the interplay between material composition, shell thickness, and tapering in determining the bending. The simulation results are in good agreement with the experimental bending curvature, reproducing the radius of 4.3 µm (±10%), for the 2.3 µm long nanowire. The InP core of the bent heterostructure was found to be compressed at about 2%. This report provides evidence of shape control and strain engineering in nanostructures, specifically through the exchange of group-V materials in III–V nanowire growth. Full article
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Open AccessArticle
Structure and Electronic Properties of InSb Nanowires Grown in Flexible Polycarbonate Membranes
Nanomaterials 2019, 9(9), 1260; https://doi.org/10.3390/nano9091260 - 05 Sep 2019
Abstract
A dense array of vertically aligned indium antimonide (InSb) nanowires with high aspect ratio (diameter 150 nm, length 20 μ m) were grown in the pores of a track-etched polycarbonate membrane via a one-step electrochemical method. There are several reports on InSb nanowire [...] Read more.
A dense array of vertically aligned indium antimonide (InSb) nanowires with high aspect ratio (diameter 150 nm, length 20 μ m) were grown in the pores of a track-etched polycarbonate membrane via a one-step electrochemical method. There are several reports on InSb nanowire growth in the pores of a mechanically rigid, nano-channel alumina template (NCA), where nanowire growth occurs in the pores of the NCA. This work on InSb nanowire growth in pores of track-etched polycarbonate (PC) membrane sheds light on the various factors that affect nucleation and nanowire growth. The average length and diameter of the as-grown nanowires was about 10 μ m and 150 nm, respectively. Two possible mechanisms accounting for two different morphologies of the as-grown nanowires are proposed. The polycrystallinity observed in some of the nanowires is explained using the 3D ‘nucleation-coalescence’ mechanism. On the other hand, single crystal nanowires with a high density of twin defects and stacking faults grow epitaxially by a two-dimensional (2D) nucleation/growth mechanism. To assess the electrical quality of the nanowires, two- and four-terminal devices were fabricated using a single InSb nanowire contacted by two Ni electrodes. It was found that, at low bias, the ohmic current is controlled by charge diffusion from the bulk contacts. On the other hand, at high bias, the effects of space charge limited current (SCLC) are evident in the current–voltage behavior, characteristic of transport through structures with reduced electrostatic screening. A cross-over from ohmic to SCLC occurs at about 0.14 V, yielding a free carrier concentration of the order of 10 14 cm 3 . Full article
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Open AccessArticle
Formation of Fe-Te Nanostructures during in Situ Fe Heavy Doping of Bi2Te3
Nanomaterials 2019, 9(5), 782; https://doi.org/10.3390/nano9050782 - 22 May 2019
Abstract
To study the in situ doping effect upon monotonically increasing dopant concentration, a Bi2Te3 layer doped with Fe up to ~6.9% along the growth direction was fabricated by the molecular beam epitaxy (MBE) technique. Its resistance versus temperature curve displays [...] Read more.
To study the in situ doping effect upon monotonically increasing dopant concentration, a Bi2Te3 layer doped with Fe up to ~6.9% along the growth direction was fabricated by the molecular beam epitaxy (MBE) technique. Its resistance versus temperature curve displays a superconductivity transition at about 12.3 K. Detailed structural and chemical analysis via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS) reveal that this layer consists of two types of unexpected Fe-Te nanostructures: one is FeTe thin layer formed near the surface, and the other is FeTe2 nanorod embedded in the Bi2Te3 layer. Based on the results of further electrical and magnetotransport studies, it is likely that the observed superconductivity originates from the interface between the FeTe nanostructure and the neighboring Bi2Te3 layer. We have addressed the formation mechanisms of the observed nanostructures, which is attributed to the strong reaction between Fe and Te atoms during the growth process. The findings of this study also provide an unusual approach to synthesizing nanostructures via heavy doping if the dopant element is strongly reactive with an element in the host matrix. Full article
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Open AccessArticle
Design and Regulation of Novel MnFe2O4@C Nanowires as High Performance Electrode for Supercapacitor
Nanomaterials 2019, 9(5), 777; https://doi.org/10.3390/nano9050777 - 21 May 2019
Cited by 1
Abstract
Bimetallic oxides have been considered as potential candidates for supercapacitors due to their relatively high electric conductivity, abundant redox reactions and cheapness. However, nanoparticle aggregation and huge volume variation during charging-discharging procedures make it hard for them to be applied widely. In this [...] Read more.
Bimetallic oxides have been considered as potential candidates for supercapacitors due to their relatively high electric conductivity, abundant redox reactions and cheapness. However, nanoparticle aggregation and huge volume variation during charging-discharging procedures make it hard for them to be applied widely. In this work, one-dimensional (1D) MnFe2O4@C nanowires were in-situ synthesized via a simply modified micro-emulsion technique, followed by thermal treatment. The novel 1D and core-shell architecture, and in-situ carbon coating promote its electric conductivity and porous feature. Due to these advantages, the MnFe2O4@C electrode exhibits a high specific capacitance of 824 F·g−1 at 0.1 A·g−1 and remains 476 F·g−1 at 5 A·g−1. After 10,000 cycles, the capacitance retention of the MnFe2O4@C electrode is up to 93.9%, suggesting its excellent long-term cycling stability. After assembling with activated carbon (AC) to form a MnFe2O4@C//AC device, the energy density of this MnFe2O4@C//AC device is 27 W·h·kg−1 at a power density of 290 W·kg−1, and remains at a 10 W·h·kg−1 energy density at a high power density of 9300 W·kg−1. Full article
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Open AccessArticle
A Ferroelectric-Photovoltaic Effect in SbSI Nanowires
Nanomaterials 2019, 9(4), 580; https://doi.org/10.3390/nano9040580 - 09 Apr 2019
Cited by 2
Abstract
A ferroelectric-photovoltaic effect in nanowires of antimony sulfoiodide (SbSI) is presented for the first time. Sonochemically prepared SbSI nanowires have been characterized using high-resolution transmission electron microscopy (HRTEM) and optical diffuse reflection spectroscopy (DRS). The temperature dependences of electrical properties of the fabricated [...] Read more.
A ferroelectric-photovoltaic effect in nanowires of antimony sulfoiodide (SbSI) is presented for the first time. Sonochemically prepared SbSI nanowires have been characterized using high-resolution transmission electron microscopy (HRTEM) and optical diffuse reflection spectroscopy (DRS). The temperature dependences of electrical properties of the fabricated SbSI nanowires have been investigated too. The indirect forbidden energy gap EgIf = 1.862 (1) eV and Curie temperature TC = 291 (2) K of SbSI nanowires have been determined. Aligned SbSI nanowires have been deposited in an electric field between Pt electrodes on alumina substrate. The photoelectrical response of such a prepared ferroelectric-photovoltaic (FE-PV) device can be switched using a poling electric field and depends on light intensity. The photovoltage, generated under λ = 488 nm illumination of Popt = 127 mW/cm2 optical power density, has reached UOC = 0.119 (2) V. The presented SbSI FE-PV device is promising for solar energy harvesting as well as for application in non-volatile memories based on the photovoltaic effect. Full article
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Open AccessArticle
Applied Stress-Assisted Growth of Single Crystal γ-Fe2O3 Nanowires
Nanomaterials 2018, 8(12), 1037; https://doi.org/10.3390/nano8121037 - 12 Dec 2018
Abstract
It is difficult to obtain γ-Fe2O3 nanostructures by heating iron substrate in ambient conditions because γ-Fe2O3 is less thermodynamically stable than α-Fe2O3. In this work, we synthesize γ-Fe2O3 nanowires by [...] Read more.
It is difficult to obtain γ-Fe2O3 nanostructures by heating iron substrate in ambient conditions because γ-Fe2O3 is less thermodynamically stable than α-Fe2O3. In this work, we synthesize γ-Fe2O3 nanowires by heating iron particles under an external force. The stacking style of iron and oxygen ions under a strong shearing stress tends to adopt the γ-Fe2O3 structure regardless of the thermodynamic restriction. These γ-Fe2O3 nanowires exhibit a clear ferromagnetic property. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurements confirm that γ-phase structure appears only under the applied external force during the heating period. A window of the magnitude of the external force is found to help the nanowire growth on iron particles. The growth mechanism of γ-Fe2O3 nanowires other than α-Fe2O3 under the external force is discussed and an applied stress-assisted growth model is proposed. This work presents an easy approach to produce ferromagnetic iron oxide nanowires on a large scale. Full article
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Open AccessArticle
Synthesis of Amorphous InSb Nanowires and a Study of the Effects of Laser Radiation and Thermal Annealing on Nanowire Crystallinity
Nanomaterials 2018, 8(8), 607; https://doi.org/10.3390/nano8080607 - 09 Aug 2018
Cited by 3
Abstract
Although various synthesis and characterization strategies have been employed for the synthesis of crystalline nanowires, there is very little work done on development of low-dimensional amorphous semiconductors. This paper presents a simple strategy to grow amorphous InSb (a- [...] Read more.
Although various synthesis and characterization strategies have been employed for the synthesis of crystalline nanowires, there is very little work done on development of low-dimensional amorphous semiconductors. This paper presents a simple strategy to grow amorphous InSb (a-InSb) nanowires (NWs) in a chemical vapor deposition (CVD) system. The NWs were grown on Si substrate coated with indium film and the lack of crystallinity in the as-grown stoichiometric NWs was ascertained by Raman spectroscopy and electron transport measurements. A model proposed to explain the amorphous NW growth mechanism takes into account the fact that NW growth was carried out at the high temperature ramp-up rate of 75 C/min. This high rate is believed to affect the growth kinematics and determine the arrangement of atoms in the growing NW. Raman spectrum of the as-grown sample shows a broad peak around 155 cm1, indicative of the presence of high density of homopolar Sb-Sb bonds in the amorphous matrix. It was also found that high intensity laser light induces localized crystallization of the NW, most likely due to radiation-stimulated diffusion of defects in a-InSb. The nonlinear trend of the current-voltage characteristics for individually contacted a-InSb NWs was analyzed to prove that the non-linearity is not induced by Schottky contacts. At high bias fields, space charge limited conduction was the proposed electron transport mechanism. Post-growth annealing of the as-grown a-InSb NWs was found to be very effective in causing the NWs to undergo a phase transition from amorphous to crystalline. Full article
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Review

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Open AccessReview
Review on Quasi One-Dimensional CdSe Nanomaterials: Synthesis and Application in Photodetectors
Nanomaterials 2019, 9(10), 1359; https://doi.org/10.3390/nano9101359 - 23 Sep 2019
Abstract
During the past 15 years, quasi one-dimensional (1D) Cadmium Selenide (CdSe) nanomaterials have been widely investigated for high-performance electronic and optoelectronic devices, due to the unique geometrical and physical properties. In this review, recent advancements on diverse synthesis methods of 1D CdSe nanomaterials [...] Read more.
During the past 15 years, quasi one-dimensional (1D) Cadmium Selenide (CdSe) nanomaterials have been widely investigated for high-performance electronic and optoelectronic devices, due to the unique geometrical and physical properties. In this review, recent advancements on diverse synthesis methods of 1D CdSe nanomaterials and the application in photodetectors have been illustrated in detail. First, several bottom-up synthesis methods of 1D CdSe nanomaterials have been introduced, including the vapor-liquid-solid method, the solution-liquid-solid method, and electrochemical deposition, etc. Second, the discussion on photodetectors based on 1D CdSe nanomaterials has been divided into three parts, including photodiodes, photoconductors, and phototransistors. Besides, some new mechanisms (such as enhancement effect of localized surface plasmon, optical quenching effect of photoconductivity, and piezo-phototronic effect), which can be utilized to enhance the performance of photodetectors, have also been elaborated. Finally, some major challenges and opportunities towards the practical integration and application of 1D CdSe nanomaterials in photodetectors have been discussed, which need to be further investigated in the future. Full article
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