Special Issue "2D Materials for Advanced Devices"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Electronic Materials".

Deadline for manuscript submissions: 30 November 2020.

Special Issue Editor

Dr. Rafik Addou
Website
Guest Editor
School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, Oregon 97331, USA
Interests: 2D materials; scanning probe microscopy; XPS, nanofabrication; thin films, interface and surface science

Special Issue Information

Dear Colleagues,

Since the isolation of the first single layer of graphite (graphene) and the revelation of its outstanding optical, electrical, and mechanical properties, increased interests have focused on all existing layered materials and in developing novel 2D nanomaterials. Two-dimensional materials are extensively used in various 2D/flexible technological applications such as nanoelectronics, optoelectronics, energy, composites, sensing, filtration, nanocoating, life science, and medicine. In the last few years, remarkable efforts have been made towards the growth of high-quality, atomically thin, and large domain films, as well as a realizing electronic grade 2D materials. Except for graphene, immature 2D materials requires tremendous work in making a substantial transition from reporting the fundamental properties and the experimental proof-of-concept (feasibility) to the technology development and validation.

The aim of this Special Issue, entitled “2D Materials for Advanced Devices”, is to offer the latest cutting-edge research and development of 2D technology. This issue seeks to publish recent advances in the synthesis of novel and high-quality 2D materials, device fabrication and testing, integration challenges solving, and surface and interface engineering. Both experimental and theoretical articles will be published in this Special Issue, focusing on the state-of-the-art of recent research on the engineering and developments of 2D materials for advanced devices such as graphene and related materials, hexagonal boron nitride, transition metal dichalcogenides, silicene, phosphorene, tellurene, topological insulators, oxides, nitrides, carbides, hydroxides, perovskites, MOFs, MXenes, etc.

As a renowned expert in the field of 2D nanomaterials, I would like to invite you to submit a manuscript to foster the “2D Materials for Advanced Devices Special Issue.

Dr. Rafik Addou
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. Materials 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 2000 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

  • Graphene and its analogs (graphane, graphene oxide, fluorographene, etc.)
  • Monoelement 2D materials: silicene, germanene, borophene, phosphorene, arsenene, stanene, bismuthene, tellurene, etc.
  • 2D chalcogenides: WSe2, MoTe2, TaS2, GaTe, InSe, Sb2Te3, Bi2Se3, etc.
  • 2D oxides, carbides, and nitrides
  • 2D perovskites, hydroxides, MOFs, MAX phases, MXenes, metal halides, and other novel 2D materials.
  • 2D Materials engineering: surfaces, interfaces, heterostructures, alloying, passivation, functionalization, etching, 0D and 1D structures from 2D materials, 2D quantum wells, etc.
  • 2D advanced devices and applications
  • Physics and materials science at 2D limit

Published Papers (8 papers)

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Research

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Open AccessArticle
Ion-Locking in Solid Polymer Electrolytes for Reconfigurable Gateless Lateral Graphene p-n Junctions
Materials 2020, 13(5), 1089; https://doi.org/10.3390/ma13051089 - 01 Mar 2020
Cited by 2
Abstract
A gateless lateral p-n junction with reconfigurability is demonstrated on graphene by ion-locking using solid polymer electrolytes. Ions in the electrolytes are used to configure electric-double-layers (EDLs) that induce p- and n-type regions in graphene. These EDLs are locked in place [...] Read more.
A gateless lateral p-n junction with reconfigurability is demonstrated on graphene by ion-locking using solid polymer electrolytes. Ions in the electrolytes are used to configure electric-double-layers (EDLs) that induce p- and n-type regions in graphene. These EDLs are locked in place by two different electrolytes with distinct mechanisms: (1) a polyethylene oxide (PEO)-based electrolyte, PEO:CsClO4, is locked by thermal quenching (i.e., operating temperature < Tg (glass transition temperature)), and (2) a custom-synthesized, doubly-polymerizable ionic liquid (DPIL) is locked by thermally triggered polymerization that enables room temperature operation. Both approaches are gateless because only the source/drain terminals are required to create the junction, and both show two current minima in the backgated transfer measurements, which is a signature of a graphene p-n junction. The PEO:CsClO4 gated p-n junction is reconfigured to n-p by resetting the device at room temperature, reprogramming, and cooling to T < Tg. These results show an alternate approach to locking EDLs on 2D devices and suggest a path forward to reconfigurable, gateless lateral p-n junctions with potential applications in polymorphic logic circuits. Full article
(This article belongs to the Special Issue 2D Materials for Advanced Devices)
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Open AccessFeature PaperArticle
Monte Carlo Study of Electronic Transport in Monolayer InSe
Materials 2019, 12(24), 4210; https://doi.org/10.3390/ma12244210 - 14 Dec 2019
Cited by 6
Abstract
The absence of a band gap in graphene makes it of minor interest for field-effect transistors. Layered metal chalcogenides have shown great potential in device applications thanks to their wide bandgap and high carrier mobility. Interestingly, in the ever-growing library of two-dimensional (2D) [...] Read more.
The absence of a band gap in graphene makes it of minor interest for field-effect transistors. Layered metal chalcogenides have shown great potential in device applications thanks to their wide bandgap and high carrier mobility. Interestingly, in the ever-growing library of two-dimensional (2D) materials, monolayer InSe appears as one of the new promising candidates, although still in the initial stage of theoretical studies. Here, we present a theoretical study of this material using density functional theory (DFT) to determine the electronic band structure as well as the phonon spectrum and electron-phonon matrix elements. The electron-phonon scattering rates are obtained using Fermi’s Golden Rule and are used in a full-band Monte Carlo computer program to solve the Boltzmann transport equation (BTE) to evaluate the intrinsic low-field mobility and velocity-field characteristic. The electron-phonon matrix elements, accounting for both long- and short-range interactions, are considered to study the contributions of different scattering mechanisms. Since monolayer InSe is a polar piezoelectric material, scattering with optical phonons is dominated by the long-range interaction with longitudinal optical (LO) phonons while scattering with acoustic phonons is dominated by piezoelectric scattering with the longitudinal (LA) branch at room temperature (T = 300 K) due to a lack of a center of inversion symmetry in monolayer InSe. The low-field electron mobility, calculated considering all electron-phonon interactions, is found to be 110 cm2V−1s−1, whereas values of 188 cm2V−1s−1 and 365 cm2V−1s−1 are obtained considering the long-range and short-range interactions separately. Therefore, the calculated electron mobility of monolayer InSe seems to be competitive with other previously studied 2D materials and the piezoelectric properties of monolayer InSe make it a suitable material for a wide range of applications in next generation nanoelectronics. Full article
(This article belongs to the Special Issue 2D Materials for Advanced Devices)
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Open AccessFeature PaperArticle
Electronic Transport Properties of Silicane Determined from First Principles
Materials 2019, 12(18), 2935; https://doi.org/10.3390/ma12182935 - 11 Sep 2019
Cited by 7
Abstract
Silicane, a hydrogenated monolayer of hexagonal silicon, is a candidate material for future complementary metal-oxide-semiconductor technology. We determined the phonon-limited mobility and the velocity-field characteristics for electrons and holes in silicane from first principles, relying on density functional theory. Transport calculations were performed [...] Read more.
Silicane, a hydrogenated monolayer of hexagonal silicon, is a candidate material for future complementary metal-oxide-semiconductor technology. We determined the phonon-limited mobility and the velocity-field characteristics for electrons and holes in silicane from first principles, relying on density functional theory. Transport calculations were performed using a full-band Monte Carlo scheme. Scattering rates were determined from interpolated electron–phonon matrix elements determined from density functional perturbation theory. We found that the main source of scattering for electrons and holes was the ZA phonons. Different cut-off wavelengths ranging from 0.58 nm to 16 nm were used to study the possible suppression of the out-of-plane acoustic (ZA) phonons. The low-field mobility of electrons (holes) was obtained as 5 (10) cm2/(Vs) with a long wavelength ZA phonon cut-off of 16 nm. We showed that higher electron (hole) mobilities of 24 (101) cm2/(Vs) can be achieved with a cut-off wavelength of 4 nm, while completely suppressing ZA phonons results in an even higher electron (hole) mobility of 53 (109) cm2/(Vs). Velocity-field characteristics showed velocity saturation at 3 × 105 V/cm, and negative differential mobility was observed at larger fields. The silicane mobility was competitive with other two-dimensional materials, such as transition-metal dichalcogenides or phosphorene, predicted using similar full-band Monte Carlo calculations. Therefore, silicon in its most extremely scaled form remains a competitive material for future nanoscale transistor technology, provided scattering with out-of-plane acoustic phonons could be suppressed. Full article
(This article belongs to the Special Issue 2D Materials for Advanced Devices)
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Open AccessArticle
New Findings on Multilayer Silicene on Si(111)√3×√3R30°–Ag Template
Materials 2019, 12(14), 2258; https://doi.org/10.3390/ma12142258 - 13 Jul 2019
Cited by 2
Abstract
We report new findings on multilayer silicene grown on Si(111)√3 × √3 R30°–Ag template, after the recent first compelling experimental evidence of its synthesis. Low-energy electron diffraction, reflection high-energy electron diffraction, and energy-dispersive grazing incidence X-ray diffraction measurements were performed to show up [...] Read more.
We report new findings on multilayer silicene grown on Si(111)√3 × √3 R30°–Ag template, after the recent first compelling experimental evidence of its synthesis. Low-energy electron diffraction, reflection high-energy electron diffraction, and energy-dispersive grazing incidence X-ray diffraction measurements were performed to show up the fingerprints of √3 × √3 multilayer silicene. Angle-resolved photoemission spectroscopy displayed new features in the second surface Brillouin zone, attributed to the multilayer silicene on Si(111)√3 × √3 R30°–Ag. Band-structure dispersion theoretical calculations performed on a model of three honeycomb stacked layers, silicene grown on Si(111)√3 × √3 R30°-Ag surface confirm the experimental results. Full article
(This article belongs to the Special Issue 2D Materials for Advanced Devices)
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Open AccessArticle
High-throughput Production of ZnO-MoS2-Graphene Heterostructures for Highly Efficient Photocatalytic Hydrogen Evolution
Materials 2019, 12(14), 2233; https://doi.org/10.3390/ma12142233 - 11 Jul 2019
Cited by 9
Abstract
High-throughput production of highly efficient photocatalysts for hydrogen evolution remains a considerable challenge for materials scientists. Here, we produced extremely uniform high-quality graphene and molybdenum disulfide (MoS2) nanoplatelets through the electrochemical-assisted liquid-phase exfoliation, out of which we subsequently fabricated MoS2 [...] Read more.
High-throughput production of highly efficient photocatalysts for hydrogen evolution remains a considerable challenge for materials scientists. Here, we produced extremely uniform high-quality graphene and molybdenum disulfide (MoS2) nanoplatelets through the electrochemical-assisted liquid-phase exfoliation, out of which we subsequently fabricated MoS2/graphene van der Waals heterostructures. Ultimately, zinc oxide (ZnO) nanoparticles were deposited into these two-dimensional heterostructures to produce an artificial ZnO/MoS2/graphene nanocomposite. This new composite experimentally exhibited an excellent photocatalytic efficiency in hydrogen evolution under the sunlight illumination ( λ > 400   n m ), owing to the extremely high electron mobilities in graphene nanoplatelets and the significant visible-light absorptions of MoS2. Moreover, due to the synergistic effects in MoS2 and graphene, the lifetime of excited carriers increased dramatically, which considerably improved the photocatalytic efficiency of the ZnO/MoS2/graphene heterostructure. We conclude that the novel artificial heterostructure presented here shows great potential for the high-efficient photocatalytic hydrogen generation and the high throughput production of visible-light photocatalysts for industrial applications. Full article
(This article belongs to the Special Issue 2D Materials for Advanced Devices)
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Open AccessArticle
High Optical Response of Niobium-Doped WSe2-Layered Crystals
Materials 2019, 12(7), 1161; https://doi.org/10.3390/ma12071161 - 10 Apr 2019
Cited by 1
Abstract
The optical properties of WSe2-layered crystals doped with 0.5% niobium (Nb) grown by the chemical vapor transport method were characterized by piezoreflectance (PzR), photoconductivity (PC) spectroscopy, frequency-dependent photocurrent, and time-resolved photoresponse. With the incorporation of 0.5% Nb, the WSe2 crystal [...] Read more.
The optical properties of WSe2-layered crystals doped with 0.5% niobium (Nb) grown by the chemical vapor transport method were characterized by piezoreflectance (PzR), photoconductivity (PC) spectroscopy, frequency-dependent photocurrent, and time-resolved photoresponse. With the incorporation of 0.5% Nb, the WSe2 crystal showed slight blue shifts in the near band edge excitonic transitions and exhibited strongly enhanced photoresponsivity. Frequency-dependent photocurrent and time-resolved photoresponse were measured to explore the kinetic decay processes of carriers. Our results show the potential application of layered crystals for photodetection devices based on Nb-doped WSe2-layered crystals. Full article
(This article belongs to the Special Issue 2D Materials for Advanced Devices)
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Open AccessArticle
High-κ Dielectric on ReS2: In-Situ Thermal Versus Plasma-Enhanced Atomic Layer Deposition of Al2O3
Materials 2019, 12(7), 1056; https://doi.org/10.3390/ma12071056 - 30 Mar 2019
Cited by 2
Abstract
We report an excellent growth behavior of a high-κ dielectric on ReS2, a two-dimensional (2D) transition metal dichalcogenide (TMD). The atomic layer deposition (ALD) of an Al2O3 thin film on the UV-Ozone pretreated surface of ReS2 yields [...] Read more.
We report an excellent growth behavior of a high-κ dielectric on ReS2, a two-dimensional (2D) transition metal dichalcogenide (TMD). The atomic layer deposition (ALD) of an Al2O3 thin film on the UV-Ozone pretreated surface of ReS2 yields a pinhole free and conformal growth. In-situ half-cycle X-ray photoelectron spectroscopy (XPS) was used to monitor the interfacial chemistry and ex-situ atomic force microscopy (AFM) was used to evaluate the surface morphology. A significant enhancement in the uniformity of the Al2O3 thin film was deposited via plasma-enhanced atomic layer deposition (PEALD), while pinhole free Al2O3 was achieved using a UV-Ozone pretreatment. The ReS2 substrate stays intact during all different experiments and processes without any formation of the Re oxide. This work demonstrates that a combination of the ALD process and the formation of weak S–O bonds presents an effective route for a uniform and conformal high-κ dielectric for advanced devices based on 2D materials. Full article
(This article belongs to the Special Issue 2D Materials for Advanced Devices)
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Review

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Open AccessFeature PaperReview
Contacts for Molybdenum Disulfide: Interface Chemistry and Thermal Stability
Materials 2020, 13(3), 693; https://doi.org/10.3390/ma13030693 - 04 Feb 2020
Cited by 1
Abstract
In this review on contacts with MoS2, we consider reports on both interface chemistry and device characteristics. We show that there is considerable disagreement between reported properties, at least some of which may be explained by variability in the properties of [...] Read more.
In this review on contacts with MoS2, we consider reports on both interface chemistry and device characteristics. We show that there is considerable disagreement between reported properties, at least some of which may be explained by variability in the properties of geological MoS2. Furthermore, we highlight that while early experiments using photoemission to study the interface behavior of metal-MoS2 showed a lack of Fermi-level pinning, device measurements repeatedly confirm that the interface is indeed pinned. Here we suggest that a parallel conduction mechanism enabled by metallic defects in the MoS2 materials may explain both results. We note that processing conditions during metal depositions on MoS2 can play a critical role in the interface chemistry, with differences between high vacuum and ultra-high vacuum being particularly important for low work function metals. This can be used to engineer the interfaces by using thin metal-oxide interlayers to protect the MoS2 from reactions with the metals. We also report on the changes in the interfaces that can occur at high temperature which include enhanced reactions between Ti or Cr and MoS2, diffusion of Ag into MoS2, and delamination of Fe. What is clear is that there is a dearth of experimental work that investigates both the interface chemistry and device properties in parallel. Full article
(This article belongs to the Special Issue 2D Materials for Advanced Devices)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Author: Rafik Addou
Affiliation: Oregon State University, USA

Author:Stephen McDonnell
Affiliation:The University of Virginia

Author:Massimo V Fischetti
Affiliation:The University of Texas at Dallas

Author:Christopher Hinkle
Affiliation:The University of Texas at Dallas

Author:Chadwin D. Young
Affiliation:The University of Texas at Dallas

Author:Yu-Chuan Lin
Affiliation:Oak Ridge National Laboratory; Penn State University

Author:Santosh KC
Affiliation:Oak Ridge National Laboratory

Author:Lee Walsh
Affiliation:Wesleyan University

Author:William Vandenberghe
Affiliation:The University of Texas at Dallas

Author:Irene Paola De Padova
Affiliation: ISM - CNR - Rome, Italy

Author:Susan Fullerton
Affiliation:University of Pittsburgh

Author:Alan Seabaugh
Affiliation:University of Notre Dame

 

 

 

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