Special Issue "Advances in Functional Materials and Devices for Semiconductor and Energy Applications"

A special issue of Coatings (ISSN 2079-6412).

Deadline for manuscript submissions: closed (30 September 2020).

Special Issue Editor

Prof. Dr. You Seung Rim
Website
Guest Editor
School of Intelligent Mechatronics Engineering, Sejong University
Interests: printed electronics; biosensors; oxide semiconductors; thin-film transistors; power semiconductor
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Recently, new concept-based sensor platforms, such as non-invasive monitoring of body fluids, electric-skin-based pressure-sensitive and stretchable stimulation, particle matter detection, and highly-selective gas detection, have been attracting attention. These sensing platforms can be produced by applying unconventional structures with high strechability, 1D–3D nanomaterials for high sensitivity, and the immobilization of specific receptors for selective reactions. Of course, there are no restrictions in terms of materials, structures, and hybrid components, so many different approaches can be pursued with these platforms irrespective of whether the systems involve organic or inorganic materials.

Another key issue in the processing of sensor materials, such as spray pyrolysis, the ultrathin coating process via a solution process, or ink-jet printing, is the need for high sensitivity and selectivity with a reasonably low cost.

The use of sensor devices can be expanded to diverse applications, such as energy conversion with photocatalytic activity, photovoltaics, and triboelectrics regarding energy harvesting for the best decision of a certain situation through the acquistion of big data. 

This aim of this Special Issue is to focus the research on multidisciplinary material synthesis, processing, and characterization of functional metal oxides, organic/inorganic hybrids, organic semiconductors, and their applications in various devices on the following topics, among others:

  • Synthesis and processing of inorganic materials for highly efficient energy conversion systems;
  • Device performance of nano/micro sensor platforms for biological and environmental conditions;
  • Synthesis and characterization of 1D/2D/3D nanomaterials for highly-sensitive sensors;
  • New materials for highly-sensitive and selective sensors;
  • Structural studies of stretchable and flexible sensors;
  • Printable sensing materials and devices.

Prof. Dr. You Seung Rim
Guest Editor

Manuscript Submission Information

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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. Coatings 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 1800 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

  • nanomaterials
  • printing process
  • inorganic semiconductors
  • organic semiconductors
  • inorganic/organic hybrid
  • sensor devices
  • stretchable electronics

Published Papers (11 papers)

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Research

Open AccessArticle
Preparation and Characterization of Quinoxaline-Pyrene-Based Conjugated Copolymers for Organic Photovoltaic Devices
Coatings 2020, 10(11), 1098; https://doi.org/10.3390/coatings10111098 - 16 Nov 2020
Viewed by 456
Abstract
In this study, two novel conjugated polymers, poly(4,5,9,10-tetrakis((2-ethylhexyl)oxy]pyrene-alt-2,3-bis(3-(octyloxy)phenyl)-5,8-di(2-thienyl)-6,7-difluoroquinoxaline) (PPyQxff) and poly(4,5,9,10-tetrakis((2-ethylhexyl)oxy)pyren-alt-2,3-bis(3-(octyloxy)phenyl)-5,8-di(2-thienyl)quinoxaline) (PPyQx), consisting of quinoxaline units with and without fluorine substituents, as electron-accepting moieties and pyrene flanked with dithienyl units as electron-donating moieties were prepared via Stille polymerization reactions for use as electron [...] Read more.
In this study, two novel conjugated polymers, poly(4,5,9,10-tetrakis((2-ethylhexyl)oxy]pyrene-alt-2,3-bis(3-(octyloxy)phenyl)-5,8-di(2-thienyl)-6,7-difluoroquinoxaline) (PPyQxff) and poly(4,5,9,10-tetrakis((2-ethylhexyl)oxy)pyren-alt-2,3-bis(3-(octyloxy)phenyl)-5,8-di(2-thienyl)quinoxaline) (PPyQx), consisting of quinoxaline units with and without fluorine substituents, as electron-accepting moieties and pyrene flanked with dithienyl units as electron-donating moieties were prepared via Stille polymerization reactions for use as electron donor materials in bulk heterojunction (BHJ) solar cells. PPyQxff and PPyQx were characterized by X-ray powder diffraction (XRD), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), cyclic voltammetry (CV), UV−VIS absorption, and nuclear magnetic resonance (NMR) spectroscopy. PPyQxff and PPyQx revealed excellent solution processability in common organic solvents. PPyQxff and PPyQx presented decomposition temperatures above 300 °C. The inclusion of F atoms to the quinoxaline moiety made a slight reduction in the highest occupied molecular orbital (HOMO) level, relative to the unfluorinated polymer, but had no impact on the lowest unoccupied molecular orbital (LUMO) level. PPyQxff and PPyQx exhibited similar physical properties with strong and broad absorbance from 400 to 700 nm and an optical band-gap energy of 1.77 eV. The X-ray powder diffraction study indicated that PPyQxff possessed a reduced π–π stacking distance relative to PPyQx. Full article
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Open AccessArticle
Zn-Al Layered Double Hydroxide Thin Film Fabricated by the Sputtering Method and Aqueous Solution Treatment
Coatings 2020, 10(7), 669; https://doi.org/10.3390/coatings10070669 - 13 Jul 2020
Cited by 1 | Viewed by 739
Abstract
Zn-Al layered double hydroxides (LDHs) were synthesized herein via a simple process. First, Al-doped ZnO film was deposited onto a glass substrate using the facing target sputtering system. Successful synthesis of the Zn–Al LDH was achieved via a treatment process using an aqueous [...] Read more.
Zn-Al layered double hydroxides (LDHs) were synthesized herein via a simple process. First, Al-doped ZnO film was deposited onto a glass substrate using the facing target sputtering system. Successful synthesis of the Zn–Al LDH was achieved via a treatment process using an aqueous solution which contains NO3 anions. X-ray diffraction analysis confirmed that it was consistent with the previous Zn–Al LDH synthesis experiment data, and the calculated d-value was 9.1 Å. Scanning electron microscopy observations revealed that the as-synthesized sample had a plate-like structure. Full article
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Open AccessArticle
Synergistic Design of Anatase–Rutile TiO2 Nanostructured Heterophase Junctions toward Efficient Photoelectrochemical Water Oxidation
Coatings 2020, 10(6), 557; https://doi.org/10.3390/coatings10060557 - 11 Jun 2020
Cited by 1 | Viewed by 966
Abstract
Synergistically designing porous nanostructures and appropriate band alignment for TiO2 heterophase junctions is key to efficient charge transfer, which is crucial in enhancing photoelectrochemical (PEC) water splitting for hydrogen production. Here, we investigate the efficiency of PEC water oxidation in anatase–rutile TiO [...] Read more.
Synergistically designing porous nanostructures and appropriate band alignment for TiO2 heterophase junctions is key to efficient charge transfer, which is crucial in enhancing photoelectrochemical (PEC) water splitting for hydrogen production. Here, we investigate the efficiency of PEC water oxidation in anatase–rutile TiO2 nanostructured heterophase junctions that present the type-II band alignment. We specifically prove the importance of a phase alignment in heterophase junction for effective charge separation. The TiO2 heterophase junctions were prepared by transferring TiO2 nanotube (TNT) arrays onto FTO substrate with the help of a TiO2 nanoparticle (TNP) glue layer. The PEC characterization reveals that the rutile (R)-TNT/anatase (A)-TNP heterophase junction has a higher photocurrent density than those of A-TNT/R-TNP junction and anatase or rutile single phase, corresponding to twofold enhanced efficiency. This type-II band alignment of R-TNT/A-TNP for water oxidation, in which photogenerated electrons (holes) will flow from rutile (anatase) to anatase (rutile), enables to facilitate efficient electron-hole separation as well as lower the effective bandgap of heterophase junctions. This work provides insight into the functional role of heterophase junction for boosting the PEC performances of TiO2 nanostructures. Full article
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Open AccessArticle
Effect of Magnetic Field Arrangement of Facing Targets Sputtering (FTS) System on Controlling Plasma Confinement
Coatings 2020, 10(4), 321; https://doi.org/10.3390/coatings10040321 - 28 Mar 2020
Cited by 3 | Viewed by 777
Abstract
Conventional sputtering method uses a single cathode with a permanent magnet. Facing targets sputtering (FTS) methods consists of two cathodes. Because of a unique structure, FTS can prepare high quality films with low temperature and low plasma damage. During the film sputtering process, [...] Read more.
Conventional sputtering method uses a single cathode with a permanent magnet. Facing targets sputtering (FTS) methods consists of two cathodes. Because of a unique structure, FTS can prepare high quality films with low temperature and low plasma damage. During the film sputtering process, density and confinement of discharged plasma depend on the arrangement of a permanent magnet in the cathode. In this study, we designed two types of permanent magnet arrangements in the FTS system and the designed permanent magnet was inserted into two cathodes in the FTS system. The system was operated in different permanent magnet conditions, and their discharge voltage and properties of as-grown films were recorded. In the designed FTS, compared to a conventional magnetron sputtering method, the substrate temperature increased to a value under 80 °C, which is relatively low, even though the films’ sputtering process was completed. Full article
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Open AccessFeature PaperArticle
Electrical Defect State Distribution in Single Crystal ZnO Schottky Barrier Diodes
Coatings 2020, 10(3), 206; https://doi.org/10.3390/coatings10030206 - 27 Feb 2020
Cited by 1 | Viewed by 767
Abstract
The characterization of defect states in a hydrothermally grown single crystal of ZnO was performed using deep-level transient spectroscopy in the temperature range of 77–340 K. The native intrinsic defect energy level within the ZnO band gap occurred in the depletion region of [...] Read more.
The characterization of defect states in a hydrothermally grown single crystal of ZnO was performed using deep-level transient spectroscopy in the temperature range of 77–340 K. The native intrinsic defect energy level within the ZnO band gap occurred in the depletion region of ZnO Schottky barrier diodes. A major defect level was observed, with a thermal activation energy of 0.27 eV (E3) within the defect state distribution from 0.1 to 0.57 eV below the conduction band minimum. We confirmed the maximum defect concentration to be 3.66 × 1016 cm−3 at 0.27 eV (E3). As a result, we clearly confirmed the distribution of density of defect states in the ZnO band gap. Full article
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Open AccessArticle
A New Alternative Electrochemical Process for a Pre-Deposited UPD-Mn Mediated the Growth of Cu(Mn) Film by Controlling the Time during the Cu-SLRR
Coatings 2020, 10(2), 164; https://doi.org/10.3390/coatings10020164 - 11 Feb 2020
Viewed by 573
Abstract
A layer-by-layer deposition is essential for fabricating the Cu interconnects in a nanoscale-sized microelectronics because the gap-filling capability limits the film deposition step coverage on trenches/vias. Conventional layer-by-layer electrochemical deposition of Cu typically works by using two electrolytes, i.e., a sacrificial Pb electrolyte [...] Read more.
A layer-by-layer deposition is essential for fabricating the Cu interconnects in a nanoscale-sized microelectronics because the gap-filling capability limits the film deposition step coverage on trenches/vias. Conventional layer-by-layer electrochemical deposition of Cu typically works by using two electrolytes, i.e., a sacrificial Pb electrolyte and a Cu electrolyte. However, the use of a Pb electrolyte is known to cause environmental issues. This study presents an Mn monolayer, which mediated the electrochemical growth of Cu(Mn) film through a sequence of alternating an underpotential deposition (UPD) of Mn, replacing the conventionally used UPD-Pb, with a surface-limited redox replacement (SLRR) of Cu. The use of the sacrificial Mn monolayer uniquely provides redox replacement by Cu2+ owing to the standard reductive potential differences. Repeating the sequence of the UPD-Mn followed by the SLRR-Cu enables Cu(Mn) film growth in an atomic layer growth manner. Further, controlling the time of open circuit potential (OCP) during the Cu-SLRR yields a technique to control the content of the resultant Cu(Mn) film. A longer OCP time caused more replacement of the UPD-Mn by the Cu2+, thus resulting in a Cu(Mn) film with a higher Cu concentration. The proposed layer-by-layer growth method offers a wet, chemistry-based deposition capable of fabricating Cu interconnects without the use of the barrier layer and can be of interest in microelectronics. Full article
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Open AccessFeature PaperArticle
Improvement of Electrical Performance by Neutron Irradiation Treatment on IGZO Thin Film Transistors
Coatings 2020, 10(2), 147; https://doi.org/10.3390/coatings10020147 - 06 Feb 2020
Viewed by 730
Abstract
The effects of the neutron irradiation treatment on indium-gallium-zinc oxide (IGZO) are investigated as a function of the neutron irradiation time. With an increase in neutron irradiation time, the oxygen vacancies associated the oxygen deficient states increase, and both shallow and deep band [...] Read more.
The effects of the neutron irradiation treatment on indium-gallium-zinc oxide (IGZO) are investigated as a function of the neutron irradiation time. With an increase in neutron irradiation time, the oxygen vacancies associated the oxygen deficient states increase, and both shallow and deep band edge states below the conduction band also increase. Moreover, the conduction band offset continuously decreases because of the increase in the oxygen vacancies with increasing the neutron irradiation time. In IGZO TFTs with the neutron irradiation time for 10 s, superior device performance demonstrates such as the lower threshold voltage, higher field effect mobility, smaller sub-threshold gate swing, larger on-off current ratio, and improved bias stability, comparing those of other IGZO TFTs. Full article
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Open AccessArticle
The Effect of the Indium(III) Phthalocyanine Chloride Films on the Behavior of Flexible Devices of Flat and Disperse Heterojunction
Coatings 2019, 9(10), 673; https://doi.org/10.3390/coatings9100673 - 17 Oct 2019
Cited by 1 | Viewed by 1496
Abstract
By means of flat-heterojunction structures based on small semiconductor molecules (MSCs), an analysis of the indium(III) phthalocyanine chloride (In(III)PcCl) film as a constituent of optoelectronic devices was performed. The study included the behavior of In(III)PcCl playing three different roles: a donor species, an [...] Read more.
By means of flat-heterojunction structures based on small semiconductor molecules (MSCs), an analysis of the indium(III) phthalocyanine chloride (In(III)PcCl) film as a constituent of optoelectronic devices was performed. The study included the behavior of In(III)PcCl playing three different roles: a donor species, an electronic acceptor, and a hole layer carrier. The flat-heterojunction structures were prepared by vacuum deposition method that permits a controlled layer-by-layer growth of high purity films. The investigated structures were characterized by scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), UV-vis spectroscopy and optical bandgaps were obtained by Tauc’s and Cody’s methods. As the structures exhibit a large spectral absorption in the visible range, they were incorporated into flat-heterojunction devices based on flexible and rigid substrates. However, during the synthesis of those structures, the disperse heterojunction arrangement was found and indeed it showed to be more efficient than the initial flat-heterojunction. In order to complement these results, disperse heterojunction arrangement structure as well as its bandgap value were obtained by DFT calculations. Finally, the electronic behavior of both fabricated devices, disperse heterojunction and flat-heterojunction were compared. Full article
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Open AccessArticle
Boron and Nitrogen Co-Doped Porous Carbons Synthesized from Polybenzoxazines for High-Performance Supercapacitors
Coatings 2019, 9(10), 657; https://doi.org/10.3390/coatings9100657 - 11 Oct 2019
Cited by 6 | Viewed by 757
Abstract
Boron and nitrogen co-doped porous carbons (BNPC-X) were synthesized from boron-containing polybenzoxazines through carbonization and chemical activation, where X represents the weight ratio of boric acid to benzoxazine resin. The as-prepared BNPC-X were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, [...] Read more.
Boron and nitrogen co-doped porous carbons (BNPC-X) were synthesized from boron-containing polybenzoxazines through carbonization and chemical activation, where X represents the weight ratio of boric acid to benzoxazine resin. The as-prepared BNPC-X were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, element analysis and electrochemical measurements. The results show that the BNPC-0.15 possesses relatively high weight fractions of boron (2.97 wt %) and nitrogen (2.43 wt %), a homogeneous pore distribution, and remarkable electrochemical capacitive performance. It exhibits high specific capacitance (286 F·g−1 at 0.05 A·g−1), excellent rate capability (at A·g−1), and good charge–discharge stability (>92% capacitance retention after 1,000 cycles at 1.0 A·g−1) in 6 M KOH aqueous solution. Full article
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Open AccessFeature PaperArticle
Cost-Effective and High-Throughput Plasmonic Interference Coupled Nanostructures by Using Quasi-Uniform Anodic Aluminum Oxide
Coatings 2019, 9(7), 420; https://doi.org/10.3390/coatings9070420 - 30 Jun 2019
Cited by 1 | Viewed by 1376
Abstract
Large-area and uniform plasmonic nanostructures have often been fabricated by simply evaporating noble metals such as gold and silver on a variety of nanotemplates such as nanopores, nanotubes, and nanorods. However, some highly uniform nanotemplates are limited to be utilized by long, complex, [...] Read more.
Large-area and uniform plasmonic nanostructures have often been fabricated by simply evaporating noble metals such as gold and silver on a variety of nanotemplates such as nanopores, nanotubes, and nanorods. However, some highly uniform nanotemplates are limited to be utilized by long, complex, and expensive fabrication. Here, we introduce a cost-effective and high-throughput fabrication method for plasmonic interference coupled nanostructures based on quasi-uniform anodic aluminum oxide (QU-AAO) nanotemplates. Industrial aluminum, with a purity of 99.5%, and copper were used as a base template and a plasmonic material, respectively. The combination of these modifications saves more than 18 h of fabrication time and reduces the cost of fabrication 30-fold. From optical reflectance data, we found that QU-AAO based plasmonic nanostructures exhibit similar optical behaviors to highly ordered (HO) AAO-based nanostructures. By adjusting the thickness of the AAO layer and its pore size, we could easily control the optical properties of the nanostructures. Thus, we expect that QU-AAO might be effectively utilized for commercial plasmonic applications. Full article
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Open AccessArticle
Rectifying Characteristics of Thermally Treated Mo/SiC Schottky Contact
Coatings 2019, 9(6), 388; https://doi.org/10.3390/coatings9060388 - 15 Jun 2019
Viewed by 1285
Abstract
The rectifying characteristics of a Mo/SiC Schottky contact fabricated by facing targets sputtering system were investigated through current–voltage measurement. The Schottky diode parameters were extracted from the forward current–voltage characteristic curve by the Cheung and Cheung method and the Norde method. The as-deposited [...] Read more.
The rectifying characteristics of a Mo/SiC Schottky contact fabricated by facing targets sputtering system were investigated through current–voltage measurement. The Schottky diode parameters were extracted from the forward current–voltage characteristic curve by the Cheung and Cheung method and the Norde method. The as-deposited Mo/SiC Schottky contacts possessed Schottky barrier heights of 1.17 and 1.22 eV, respectively. The Schottky barrier heights of the diodes were decreased to 1.01 and 0.91 eV after annealing at 400 °C for 30 min. The ideality factor was increased from 1.14 and 1.08 to 1.51 and 1.41, respectively. This implies the presence of non-ideal behaviors due to a current transport mechanism other than ideal thermionic emission, and the non-ideal behaviors increased as a result of excessive thermal annealing. In contrast, only a negligible change was observed in the crystallographic characteristics. This result suggests that the reason for the deviation from the ideal rectifying characteristics of the Mo/SiC Schottky contact through the annealing process was the variation in the current transport mechanism, including recombination, tunneling, and/or minority carrier injection. Full article
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