Advances in Nanostructured Semiconductors and Heterojunctions

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 May 2023) | Viewed by 31591

Special Issue Editors

Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB T6G 2V4, Canada
Interests: semiconductor heterojunctions; 2D materials; halide perovskites; plasmonics; hot carrier photocatalysts; electrochemical anodization; nanotubes and nanowires; tubulin dimers and microtubules; CO2 photoreduction; sunlight-driven water splitting; microwave-nanomaterial interactions; thin film transistors
1. Nanotechnology Research Centre, National Research Council Canada, Edmonton, AB T6G 2M9, Canada
2. Future Energy Systems (FES) Research Institute, University of Alberta, Edmonton, AB T6G 1K4, Canada
Interests: spintronics; organic optoelectronics; plasmonic catalysis; photoelectrochemistry; chalcogenides; metal oxides; carbon nitrides; graphene; luminescence sensors

Special Issue Information

Dear Colleagues,

The structuring of semiconductors into nanospheres, nanowires, nanotubes, nanoshells, etc., such that at least one dimension is below 100 nm, is undertaken to engineer desired optoelectronic properties and achieve superior performance in devices such as sensors, photocatalysts, photovoltaics, thermoelectrics, light-emitting devices, transistors, electromagnetic interference shields. Such nanostructuring of semiconductors can be achieved either through bottom-up solution-based synthetic protocols or through top-down nanofabrication techniques. Likewise, the formation of nanostructured heterojunctions between two different semiconductor materials or between semiconductors and metals is also motivated by the opportunity to enhance material and device performance through mechanisms such as surface passivation, charge separation, carrier transport, carrier recombination, access to reaction sites and reactants, metamaterial effects, waveguiding effects, modulation doping. Researchers in semiconductor nanomaterials and heterojunction devices are invited to contribute original research articles or comprehensive review articles covering the most recent progress in material and device performance and/or new concepts in nanostructured semiconductors and heterojunctions relevant to applications in optoelectronics, nanophotonics, microwave engineering, sensing, or energy harvesting.  This Special Issue has a strong preference for experimental research articles, although submissions combining modeling and experimentation will also be considered. Potential topics include, but are not limited to:

  1. Core-shell chalcogenide nanoparticles, nanorods, and nanotubes
  2. Heterojunctions of 2D materials with other 2D materials (Van der Waals heterostructures)
  3. Heterojunctions of 2D materials with plasmonic nanoparticles
  4. Metal organic frameworks (MOFs) with semiconducting properties
  5. Nanostructures of relatively new or less studied compound semiconductors
  6. Nanostructured spintronic heterojunctions

Prof. Dr. Karthik Shankar
Dr. Kazi M. Alam
Guest Editors

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 submissions that pass pre-check are 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 semimonthly 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 2900 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

  • Quantum dots
  • Schottky junctions
  • Radial concentric heterojunctions
  • Hot carrier harvesting
  • Ultrafast photodetectors
  • Metamaterials
  • Purcell effect
  • Heterogeneous catalysis
  • Electron-phonon coupling
  • Spin-polarized transport

Published Papers (10 papers)

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Research

Jump to: Review

19 pages, 5048 KiB  
Article
Radial Nano-Heterojunctions Consisting of CdS Nanorods Wrapped by 2D CN:PDI Polymer with Deep HOMO for Photo-Oxidative Water Splitting, Dye Degradation and Alcohol Oxidation
Nanomaterials 2023, 13(9), 1481; https://doi.org/10.3390/nano13091481 - 26 Apr 2023
Cited by 3 | Viewed by 1764
Abstract
Solar energy harvesting using semiconductor photocatalysis offers an enticing solution to two of the biggest societal challenges, energy scarcity and environmental pollution. After decades of effort, no photocatalyst exists which can simultaneously meet the demand for excellent absorption, high quantum efficiency and photochemical [...] Read more.
Solar energy harvesting using semiconductor photocatalysis offers an enticing solution to two of the biggest societal challenges, energy scarcity and environmental pollution. After decades of effort, no photocatalyst exists which can simultaneously meet the demand for excellent absorption, high quantum efficiency and photochemical resilience/durability. While CdS is an excellent photocatalyst for hydrogen evolution, pollutant degradation and organic synthesis, photocorrosion of CdS leads to the deactivation of the catalyst. Surface passivation of CdS with 2D graphitic carbon nitrides (CN) such as g-C3N4 and C3N5 has been shown to mitigate the photocorrosion problem but the poor oxidizing power of photogenerated holes in CN limits the utility of this approach for photooxidation reactions. We report the synthesis of exfoliated 2D nanosheets of a modified carbon nitride constituted of tris-s-triazine (C6N7) linked pyromellitic dianhydride polydiimide (CN:PDI) with a deep oxidative highest occupied molecular orbital (HOMO) position, which ensures sufficient oxidizing power for photogenerated holes in CN. The heterojunction formed by the wrapping of mono-/few layered CN:PDI on CdS nanorods (CdS/CN:PDI) was determined to be an excellent photocatalyst for oxidation reactions including photoelectrochemical water splitting, dye decolorization and the photocatalytic conversion of benzyl alcohol to benzaldehyde. Extensive structural characterization using HR-TEM, Raman, XPS, etc., confirmed wrapping of few-layered CN:PDI on CdS nanorods. The increased photoactivity in CdS/CN:PDI catalyst was ascribed to facile electron transfer from CdS to CN:PDI in comparison to CdS/g-C3N4, leading to an increased electron density on the surface of the photocatalyst to drive chemical reactions. Full article
(This article belongs to the Special Issue Advances in Nanostructured Semiconductors and Heterojunctions)
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13 pages, 6565 KiB  
Article
Interface Engineering Modulated Valley Polarization in MoS2/hBN Heterostructure
Nanomaterials 2023, 13(5), 861; https://doi.org/10.3390/nano13050861 - 25 Feb 2023
Cited by 1 | Viewed by 1337
Abstract
Layered transition metal dichalcogenides (TMDs) provide a favorable research platform for the advancement of spintronics and valleytronics because of their unique spin-valley coupling effect, which is attributed to the absence of inversion symmetry coupled with the presence of time-reversal symmetry. To maneuver the [...] Read more.
Layered transition metal dichalcogenides (TMDs) provide a favorable research platform for the advancement of spintronics and valleytronics because of their unique spin-valley coupling effect, which is attributed to the absence of inversion symmetry coupled with the presence of time-reversal symmetry. To maneuver the valley pseudospin efficiently is of great importance for the fabrication of conceptual devices in microelectronics. Here, we propose a straightforward way to modulate valley pseudospin with interface engineering. An underlying negative correlation between the quantum yield of photoluminescence and the degree of valley polarization was discovered. Enhanced luminous intensities were observed in the MoS2/hBN heterostructure but with a low value of valley polarization, which was in stark contrast to those observed in the MoS2/SiO2 heterostructure. Based on the steady-state and time-resolved optical measurements, we reveal the correlation between exciton lifetime, luminous efficiency, and valley polarization. Our results emphasize the significance of interface engineering for tailoring valley pseudospin in two-dimensional systems and probably advance the progression of the conceptual devices based on TMDs in spintronics and valleytronics. Full article
(This article belongs to the Special Issue Advances in Nanostructured Semiconductors and Heterojunctions)
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16 pages, 5060 KiB  
Article
Photodetection Properties of MoS2, WS2 and MoxW1-xS2 Heterostructure: A Comparative Study
Nanomaterials 2023, 13(1), 24; https://doi.org/10.3390/nano13010024 - 21 Dec 2022
Cited by 4 | Viewed by 2482
Abstract
Layered transition metals dichalcogenides such as MoS2 and WS2 have shown a tunable bandgap, making them highly desirable for optoelectronic applications. Here, we report on one-step chemical vapor deposited MoS2, WS2 and MoxW1-xS2 [...] Read more.
Layered transition metals dichalcogenides such as MoS2 and WS2 have shown a tunable bandgap, making them highly desirable for optoelectronic applications. Here, we report on one-step chemical vapor deposited MoS2, WS2 and MoxW1-xS2 heterostructures incorporated into photoconductive devices to be examined and compared in view of their use as potential photodetectors. Vertically aligned MoS2 nanosheets and horizontally stacked WS2 layers, and their heterostructure form MoxW1-xS2, exhibit direct and indirect bandgap, respectively. To analyze these structures, various characterization methods were used to elucidate their properties including Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectrometry and high-resolution transmission electron microscopy. While all the investigated samples show a photoresponse in a broad wavelength range between 400 nm and 700 nm, the vertical MoS2 nanosheets sample exhibits the highest performances at a low bias voltage of 5 V. Our findings demonstrate a responsivity and a specific detectivity of 47.4 mA W−1 and 1.4 × 1011 Jones, respectively, achieved by MoxW1-xS2. This study offers insights into the use of a facile elaboration technique for tuning the performance of MoxW1-xS2 heterostructure-based photodetectors. Full article
(This article belongs to the Special Issue Advances in Nanostructured Semiconductors and Heterojunctions)
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11 pages, 2647 KiB  
Article
Study of Defects and Nano-patterned Substrate Regulation Mechanism in AlN Epilayers
Nanomaterials 2022, 12(22), 3937; https://doi.org/10.3390/nano12223937 - 08 Nov 2022
Cited by 2 | Viewed by 1178
Abstract
The high crystal quality and low dislocation densities of aluminum nitride (AlN) grown on flat and nano-patterned sapphire substrate that are synthesized by the metal-organic chemical vapor deposition (MOCVD) method are essential for the realization of high-efficiency deep ultraviolet light-emitting diodes. The micro-strains [...] Read more.
The high crystal quality and low dislocation densities of aluminum nitride (AlN) grown on flat and nano-patterned sapphire substrate that are synthesized by the metal-organic chemical vapor deposition (MOCVD) method are essential for the realization of high-efficiency deep ultraviolet light-emitting diodes. The micro-strains of 0.18 × 10−3 cm−2 for flat substrate AlN and 0.11 × 10−3 cm−2 for nano-patterned substrate AlN are obtained by X-ray diffractometer (XRD). The screw and edge dislocation densities of samples are determined by XRD and transmission electron microscope (TEM), and the results indicate that the nano-patterned substrates are effective in reducing the threading dislocation density. The mechanism of the variation of the threading dislocation in AlN films grown on flat and nano-patterned substrates is investigated comparatively. The etch pit density (EPD) determined by preferential chemical etching is about 1.04 × 108 cm−2 for AlN grown on a nano-patterned substrate, which is slightly smaller than the results obtained by XRD and TEM investigation. Three types of etch pits with different sizes are all revealed on the AlN surface using the hot KOH etching method. Full article
(This article belongs to the Special Issue Advances in Nanostructured Semiconductors and Heterojunctions)
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13 pages, 3824 KiB  
Article
Efficient Diode Performance with Improved Effective Carrier Lifetime and Absorption Using Bismuth Nanoparticles Passivated Silicon Nanowires
Nanomaterials 2022, 12(21), 3729; https://doi.org/10.3390/nano12213729 - 24 Oct 2022
Cited by 2 | Viewed by 1241
Abstract
In this paper, we report a novel design of bismuth nanoparticle-passivated silicon nanowire (Bi@SiNW) heterojunction composites for high diode performances and improved effective carrier lifetime and absorption properties. High-density vertically aligned SiNWs were fabricated using a simple and cost-effective silver-assisted chemical etching method. [...] Read more.
In this paper, we report a novel design of bismuth nanoparticle-passivated silicon nanowire (Bi@SiNW) heterojunction composites for high diode performances and improved effective carrier lifetime and absorption properties. High-density vertically aligned SiNWs were fabricated using a simple and cost-effective silver-assisted chemical etching method. Bi nanoparticles (BiNPs) were then anchored in these nanowires by a straightforward thermal evaporation technique. The systematic study of the morphology, elemental composition, structure, and crystallinity provided evidence for the synergistic effect between SiNWs and BiNPs. Bi@SiNWs exhibited an eight-fold enhancement of the first-order Raman scattering compared to bare silicon. Current–voltage characteristics highlighted that bismuth treatment dramatically improved the rectifying behavior and diode parameters for Bi-passivated devices over Bi-free devices. Significantly, Bi wire-filling effectively increased the minority carrier lifetime and consequently reduced the surface recombination velocity, further indicating the benign role of Bi as a surface passivation coating. Furthermore, the near-perfect absorption property of up to 97% was achieved. The findings showed that a judicious amount of Bi coating is required. In this study the reasons behind the superior improvement in Bi@SiNW’s overall properties were elucidated thoroughly. Thus, Bi@SiNW heterojunction nanocomposites could be introduced as a promising and versatile candidate for nanoelectronics, photovoltaics and optoelectronics. Full article
(This article belongs to the Special Issue Advances in Nanostructured Semiconductors and Heterojunctions)
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8 pages, 3488 KiB  
Communication
Slow-Relaxation Behavior of a Mononuclear Co(II) Complex Featuring Long Axial Co-O Bond
Nanomaterials 2022, 12(4), 707; https://doi.org/10.3390/nano12040707 - 21 Feb 2022
Cited by 1 | Viewed by 1479
Abstract
Co(II) mononuclear complex with different coordination geometry would display various of field-induced single-ion magnet (SIM) behaviors. Here, we identify a field-induced single-ion magnet in a mononuclear complex Co(H2DPA)2·H2O (H2DPA = 2,6-pyridine-dicarboxylic acid) by the hydrothermal [...] Read more.
Co(II) mononuclear complex with different coordination geometry would display various of field-induced single-ion magnet (SIM) behaviors. Here, we identify a field-induced single-ion magnet in a mononuclear complex Co(H2DPA)2·H2O (H2DPA = 2,6-pyridine-dicarboxylic acid) by the hydrothermal method. The long axial Co-O coordination bond (Co1‧‧‧O3) can be formed by Co1 and O3. Therefore, Co(II) ion is six-coordinated in a distorted elongated octahedron. AC magnetization susceptibilities show that the effective energy barrier is up to 43.28 K. This is much larger than most mononuclear Co(II). The distorted elongated octahedron caused by the axial Co-O coordination bond is responsible for the high effective energy barrier. The distribution of electron density in Co1 and O3 atoms in the long axial bond would influence the magnetic relaxation process in turn. Our work deepens the relationship between the effective energy barrier and the weak change of ligand field by long axial bonds, which would facilitate constructing SIM with high energy temperature. Full article
(This article belongs to the Special Issue Advances in Nanostructured Semiconductors and Heterojunctions)
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18 pages, 3968 KiB  
Article
Muon Irradiation of ZnO Rods: Superparamagnetic Nature Induced by Defects
Nanomaterials 2022, 12(2), 184; https://doi.org/10.3390/nano12020184 - 06 Jan 2022
Cited by 1 | Viewed by 1375
Abstract
In this work, through a combination of photoluminescence spectroscopy, X-ray powder diffraction and magnetic measurements, it is determined that ZnO rods, made hydrothermally using a combination of magnetic field with respect to the force of gravity, exhibit superparamagnetic properties which emerge from Zn [...] Read more.
In this work, through a combination of photoluminescence spectroscopy, X-ray powder diffraction and magnetic measurements, it is determined that ZnO rods, made hydrothermally using a combination of magnetic field with respect to the force of gravity, exhibit superparamagnetic properties which emerge from Zn defects. These Zn defects result in a size-dependent superparamagnetic property of the rods. Red emissions, characteristic of Zn vacancies, and magnetic susceptibility both increased with decreasing rod size. The ZnO rods have significantly larger superparamagnetic cluster sizes (one order of magnitude) and lower fluctuation rates when compared to other superparamagnetic particles. Full article
(This article belongs to the Special Issue Advances in Nanostructured Semiconductors and Heterojunctions)
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Review

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73 pages, 10240 KiB  
Review
A Comprehensive Review of Graphitic Carbon Nitride (g-C3N4)–Metal Oxide-Based Nanocomposites: Potential for Photocatalysis and Sensing
Nanomaterials 2022, 12(2), 294; https://doi.org/10.3390/nano12020294 - 17 Jan 2022
Cited by 124 | Viewed by 11416
Abstract
g-C3N4 has drawn lots of attention due to its photocatalytic activity, low-cost and facile synthesis, and interesting layered structure. However, to improve some of the properties of g-C3N4, such as photochemical stability, electrical band structure, and [...] Read more.
g-C3N4 has drawn lots of attention due to its photocatalytic activity, low-cost and facile synthesis, and interesting layered structure. However, to improve some of the properties of g-C3N4, such as photochemical stability, electrical band structure, and to decrease charge recombination rate, and towards effective light-harvesting, g-C3N4–metal oxide-based heterojunctions have been introduced. In this review, we initially discussed the preparation, modification, and physical properties of the g-C3N4 and then, we discussed the combination of g-C3N4 with various metal oxides such as TiO2, ZnO, FeO, Fe2O3, Fe3O4, WO3, SnO, SnO2, etc. We summarized some of their characteristic properties of these heterojunctions, their optical features, photocatalytic performance, and electrical band edge positions. This review covers recent advances, including applications in water splitting, CO2 reduction, and photodegradation of organic pollutants, sensors, bacterial disinfection, and supercapacitors. We show that metal oxides can improve the efficiency of the bare g-C3N4 to make the composites suitable for a wide range of applications. Finally, this review provides some perspectives, limitations, and challenges in investigation of g-C3N4–metal-oxide-based heterojunctions. Full article
(This article belongs to the Special Issue Advances in Nanostructured Semiconductors and Heterojunctions)
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24 pages, 2103 KiB  
Review
The Impact of the Surface Modification on Tin-Doped Indium Oxide Nanocomposite Properties
Nanomaterials 2022, 12(1), 155; https://doi.org/10.3390/nano12010155 - 03 Jan 2022
Cited by 2 | Viewed by 2703
Abstract
This review provides an analysis of the theoretical methods to study the effects of surface modification on structural properties of nanostructured indium tin oxide (ITO), mainly by organic compounds. The computational data are compared with experimental data such as X-ray diffraction (XRD), atomic [...] Read more.
This review provides an analysis of the theoretical methods to study the effects of surface modification on structural properties of nanostructured indium tin oxide (ITO), mainly by organic compounds. The computational data are compared with experimental data such as X-ray diffraction (XRD), atomic force microscopy (AFM) and energy-dispersive X-ray spectroscopy (EDS) data with the focus on optoelectronic and electrocatalytic properties of the surface to investigate potential relations of these properties and applications of ITO in fields such as biosensing and electronic device fabrication. Our analysis shows that the change in optoelectronic properties of the surface is mainly due to functionalizing the surface with organic molecules and that the electrocatalytic properties vary as a function of size. Full article
(This article belongs to the Special Issue Advances in Nanostructured Semiconductors and Heterojunctions)
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55 pages, 12892 KiB  
Review
Hot Electrons in TiO2–Noble Metal Nano-Heterojunctions: Fundamental Science and Applications in Photocatalysis
Nanomaterials 2021, 11(5), 1249; https://doi.org/10.3390/nano11051249 - 10 May 2021
Cited by 38 | Viewed by 5299
Abstract
Plasmonic photocatalysis enables innovation by harnessing photonic energy across a broad swathe of the solar spectrum to drive chemical reactions. This review provides a comprehensive summary of the latest developments and issues for advanced research in plasmonic hot electron driven photocatalytic technologies focusing [...] Read more.
Plasmonic photocatalysis enables innovation by harnessing photonic energy across a broad swathe of the solar spectrum to drive chemical reactions. This review provides a comprehensive summary of the latest developments and issues for advanced research in plasmonic hot electron driven photocatalytic technologies focusing on TiO2–noble metal nanoparticle heterojunctions. In-depth discussions on fundamental hot electron phenomena in plasmonic photocatalysis is the focal point of this review. We summarize hot electron dynamics, elaborate on techniques to probe and measure said phenomena, and provide perspective on potential applications—photocatalytic degradation of organic pollutants, CO2 photoreduction, and photoelectrochemical water splitting—that benefit from this technology. A contentious and hitherto unexplained phenomenon is the wavelength dependence of plasmonic photocatalysis. Many published reports on noble metal-metal oxide nanostructures show action spectra where quantum yields closely follow the absorption corresponding to higher energy interband transitions, while an equal number also show quantum efficiencies that follow the optical response corresponding to the localized surface plasmon resonance (LSPR). We have provided a working hypothesis for the first time to reconcile these contradictory results and explain why photocatalytic action in certain plasmonic systems is mediated by interband transitions and in others by hot electrons produced by the decay of particle plasmons. Full article
(This article belongs to the Special Issue Advances in Nanostructured Semiconductors and Heterojunctions)
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