Special Issue "Preparation and Properties of 2D Materials"

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

Deadline for manuscript submissions: 10 November 2019

Special Issue Editors

Guest Editor
Prof. Byungjin Cho

Department of Advanced Material Engineering, Chungbuk National University, Chungbuk 28644, Korea
Website | E-Mail
Interests: brain-inspired neuromorphic synapse devices; nanomaterial-based field effect transistors; high performance chemical sensors; synthesis of diverse 2D layered materials
Guest Editor
Dr. Yonghun Kim

Materials Center for Energy Covergence, Korea Institute of Materials Science, Gyeongsangnam-do 51508, Korea
Website | E-Mail
Interests: synthesis of emerging two-dimensional nanomaterials; semiconductor integrated process; neuromorphic synapse electronic materials and devices; advanced electrical characterization

Special Issue Information

Dear Colleagues,

Since the great success of graphene, atomically thin layered nanomaterials, briefly called 2D materials, have attracted tremendous attention as next-generation materials due to their extraordinary physical properties. Furthermore, van der Waals heterostructured architectures based on a few 2D materials have been proposed as unprecedented platforms for the implementation of versatile devices with a completely novel function or extremely high performance, bringing a paradigm shift in material research and development. Thus, diverse 2D materials beyond existing bulk materials have been widely explored and studied for promising electronic, optoelectronic, sensor, energy, structural, and bio applications. 

Especially, this Special Issue highlights the recent advances in the preparation methods of broad range of 2D materials such as graphene, transition metal dichalcogenides (MoS2, WS2, etc.), nitrides (GaN, BN, and Ca2N), organic materials (covalent frame works and 2D polymers), Mxene (Ti3C2, Ta4C3, etc.), and Xene (B, Si, Ge, and Sn) and also device applications enabling exotic physical, chemical, electrical, and optical properties. More specifically, it covers the recent progress of 2D materials on synthesis, device, analysis, and simulations for diverse applications. 

This Special Issue is open to original research articles, as well as review papers, that help researchers worldwide understand the latest trend and progress in the 2D material research field.

Prof. Byungjin Cho
Dr. Yonghun Kim
Guest Editors

Manuscript Submission Information

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Keywords

  • 2D materials
  • Graphene
  • Transition metal dichalcogenides
  • 2D nitrides
  • 2D organic materials
  • Mxene
  • Xene
  • Synthesis methods
  • Van der Waals heterostructure
  • 2D device applications
  • Properties
  • Analysis
  • Simulations

Published Papers (6 papers)

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Research

Open AccessArticle Direct Observation of Raman Spectra in Black Phosphorus under Uniaxial Strain Conditions
Nanomaterials 2019, 9(4), 566; https://doi.org/10.3390/nano9040566
Received: 22 February 2019 / Revised: 12 March 2019 / Accepted: 25 March 2019 / Published: 8 April 2019
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Abstract
In this paper, we systematically studied the Raman vibration of black phosphorus (BP) transferred onto a germanium (Ge)-coated polydimethylsiloxane (PDMS) substrate, which generates a much higher contrast in BP. This engineered flexible substrate allowed us to directly observe a much thinner BP layer [...] Read more.
In this paper, we systematically studied the Raman vibration of black phosphorus (BP) transferred onto a germanium (Ge)-coated polydimethylsiloxane (PDMS) substrate, which generates a much higher contrast in BP. This engineered flexible substrate allowed us to directly observe a much thinner BP layer on the flexible substrate at the desired location. Therefore, it enabled us to perform Raman spectroscopy immediately after exfoliation. The Raman spectra obtained from several BP layers with different thicknesses revealed that the clear peak shifting rates for the Ag1, B2g, and Ag2 modes were 0.15, 0.11, and 0.11 cm−1/nm, respectively. Using this value to identify a 2–3-layered BP, a study on the strain–Raman spectrum relationship was conducted, with a maximum uniaxial strain of 0.89%. The peak shifting of Ag1, B2g, and Ag2 caused by this uniaxial strain were measured to be 0.86, 0.63, and 0.21 cm−1/Δε, respectively. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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Open AccessArticle Direct Exfoliation of Natural SiO2-Containing Molybdenite in Isopropanol: A Cost Efficient Solution for Large-Scale Production of MoS2 Nanosheetes
Nanomaterials 2018, 8(10), 843; https://doi.org/10.3390/nano8100843
Received: 20 September 2018 / Revised: 8 October 2018 / Accepted: 12 October 2018 / Published: 17 October 2018
Cited by 1 | PDF Full-text (25599 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The cost-effective exfoliation of layered materials such as transition metal dichalcogenides into mono- or few- layers is of significant interest for various applications. This paper reports the preparation of few-layered MoS2 from natural SiO2-containing molybdenite by exfoliation in isopropanol (IPA) [...] Read more.
The cost-effective exfoliation of layered materials such as transition metal dichalcogenides into mono- or few- layers is of significant interest for various applications. This paper reports the preparation of few-layered MoS2 from natural SiO2-containing molybdenite by exfoliation in isopropanol (IPA) under mild ultrasonic conditions. One- to six-layer MoS2 nanosheets with dimensions in the range of 50-200 nm are obtained. By contrast, MoS2 quantum dots along with nanosheets are produced using N-methyl-pyrrolidone (NMP) and an aqueous solution of poly (ethylene glycol)-block-poly (propylene glycol)-block-poly (ethylene glycol) (P123) as exfoliation solutions. Compared with molybdenite, commercial bulk MoS2 cannot be exfoliated to nanosheets under the same experimental conditions. In the exfoliation process of the mineral, SiO2 associated in molybdenite plays the role of similar superfine ball milling, which significantly enhances the exfoliation efficiency. This work demonstrates that isopropanol can be used to exfoliate natural molybdenite under mild conditions to produce nanosheets, which facilitates the preparation of highly concentrated MoS2 dispersions or MoS2 in powder form due to the volatility of the solvent. Such exfoliated MoS2 nanosheets exhibit excellent photoconductivity under visible light. Hence, the direct mild exfoliation method of unrefined natural molybdenite provides a solution for low-cost and convenient production of few-layered MoS2 which is appealing for industrial applications. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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Graphical abstract

Open AccessArticle Operation Mechanism of a MoS2/BP Heterojunction FET
Nanomaterials 2018, 8(10), 797; https://doi.org/10.3390/nano8100797
Received: 20 September 2018 / Revised: 2 October 2018 / Accepted: 4 October 2018 / Published: 7 October 2018
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Abstract
The electrical characteristics and operation mechanism of a molybdenum disulfide/black phosphorus (MoS2/BP) heterojunction device are investigated herein. Even though this device showed a high on-off ratio of over 1 × 107, with a lower subthreshold swing of ~54 mV/dec [...] Read more.
The electrical characteristics and operation mechanism of a molybdenum disulfide/black phosphorus (MoS2/BP) heterojunction device are investigated herein. Even though this device showed a high on-off ratio of over 1 × 107, with a lower subthreshold swing of ~54 mV/dec and a 1fA level off current, its operating mechanism is closer to a junction field-effect transistor (FET) than a tunneling FET. The off-current of this device is governed by the depletion region in the BP layer, and the band-to-band tunneling current does not contribute to the rapid turn-on and extremely low off-current. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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Open AccessCommunication Exfoliation and Characterization of V2Se9 Atomic Crystals
Nanomaterials 2018, 8(9), 737; https://doi.org/10.3390/nano8090737
Received: 31 August 2018 / Revised: 12 September 2018 / Accepted: 18 September 2018 / Published: 18 September 2018
Cited by 1 | PDF Full-text (2316 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Mass production of one-dimensional, V2Se9 crystals, was successfully synthesized using the solid-state reaction of vanadium and selenium. Through the mechanical exfoliation method, the bulk V2Se9 crystal was easily separated to nanoribbon structure and we have confirmed that [...] Read more.
Mass production of one-dimensional, V2Se9 crystals, was successfully synthesized using the solid-state reaction of vanadium and selenium. Through the mechanical exfoliation method, the bulk V2Se9 crystal was easily separated to nanoribbon structure and we have confirmed that as-grown V2Se9 crystals consist of innumerable single V2Se9 chains linked by van der Waals interaction. The exfoliated V2Se9 flakes can be controlled thickness by the repeated-peeling method. In addition, atomic thick nanoribbon structure of V2Se9 was also obtained on a 300 nm SiO2/Si substrate. Scanning Kelvin probe microscopy analysis was used to explore the variation of work function depending on the thickness of V2Se9 flakes. We believe that these observations will be of great help in selecting suitable metal contacts for V2Se9 and that a V2Se9 crystal is expected to have an important role in future nano-electronic devices. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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Open AccessArticle Feasible Route for a Large Area Few-Layer MoS2 with Magnetron Sputtering
Nanomaterials 2018, 8(8), 590; https://doi.org/10.3390/nano8080590
Received: 20 June 2018 / Revised: 30 July 2018 / Accepted: 30 July 2018 / Published: 3 August 2018
Cited by 1 | PDF Full-text (46033 KB) | HTML Full-text | XML Full-text
Abstract
In this article, we report continuous and large-area molybdenum disulfide (MoS2) growth on a SiO2/Si substrate by radio frequency magnetron sputtering (RFMS) combined with sulfurization. The MoS2 film was synthesized using a two-step method. In the first step, [...] Read more.
In this article, we report continuous and large-area molybdenum disulfide (MoS2) growth on a SiO2/Si substrate by radio frequency magnetron sputtering (RFMS) combined with sulfurization. The MoS2 film was synthesized using a two-step method. In the first step, a thin MoS2 film was deposited by radio frequency (RF) magnetron sputtering at 400 °C with different sputtering powers. Following, the as-sputtered MoS2 film was further subjected to the sulfurization process at 600 °C for 60 min. Sputtering combined with sulfurization is a viable route for large-area few-layer MoS2 by controlling the radio-frequency magnetron sputtering power. A relatively simple growth strategy is demonstrated here that simultaneously enhances thin film quality physically and chemically. Few-layers of MoS2 are established using Raman spectroscopy, X-ray diffractometer, high-resolution field emission transmission electron microscope, and X-ray photoelectron spectroscopy measurements. Spectroscopic and microscopic results reveal that these MoS2 layers are of low disorder and well crystallized. Moreover, high quality few-layered MoS2 on a large-area can be achieved by controlling the radio-frequency magnetron sputtering power. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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Open AccessArticle α-MoO3 Crystals with a Multilayer Stack Structure Obtained by Annealing from a Lamellar MoS2/g-C3N4 Nanohybrid
Nanomaterials 2018, 8(7), 559; https://doi.org/10.3390/nano8070559
Received: 7 July 2018 / Revised: 18 July 2018 / Accepted: 20 July 2018 / Published: 22 July 2018
Cited by 1 | PDF Full-text (4998 KB) | HTML Full-text | XML Full-text
Abstract
Transition metal oxides and chalcogenides have recently attracted great attention as the next generation of 2-D materials due to their unique electronic and optical properties. In this study, a new procedure for the obtaining of highly crystalline α-MoO3 is proposed [...] Read more.
Transition metal oxides and chalcogenides have recently attracted great attention as the next generation of 2-D materials due to their unique electronic and optical properties. In this study, a new procedure for the obtaining of highly crystalline α-MoO3 is proposed as an alternative to vapor-phase synthesis. In this approach, a first reaction between molybdate, citrate and thiourea allowed to obtain MoS2, which—upon calcination at a temperature of 650 °C in the presence of g-C3N4—resulted in MoO3 with a definite plate-like shape. The colorless (or greenish) α-MoO3 nanoplates obtained with this procedure featured a multilayer stack structure, with a side-length of 1–2 μm and a thickness of several nanometers viewed along the [010] direction. The nucleation-growth of the crystal can be explained by a two-dimensional layer-by-layer mechanism favored by g-C3N4 lamellar template. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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