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Nanomaterials
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Preparation and Properties of 2D Materials
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Preparation and Properties of 2D Materials

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

Deadline for manuscript submissions: closed (10 November 2019) | Viewed by 62971

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Byungjin Cho

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Guest Editor
Department of Advanced Material Engineering, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju 28644, Chungbuk, Republic of Korea
Interests: 2D based electronics and photonics
Special Issues, Collections and Topics in MDPI journals
Dr. Yonghun Kim

E-Mail Website
Guest Editor
Materials Center for Energy Convergence, Korea Institute of Materials Science (KIMS), 797 Changwondaero, Sungsan-gu, Changwon, Gyeongnam 51508, Korea
Interests: emerging two-dimensional nanomaterials; semiconductor integrated process; neuromorphic synapse; advanced electrical characterization
Special Issues, Collections and Topics in MDPI journals

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

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

  • 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 (14 papers)

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4 pages, 182 KiB  
Editorial
Preparation and Properties of 2D Materials
by Byungjin Cho and Yonghun Kim
Nanomaterials 2020, 10(4), 764; https://doi.org/10.3390/nano10040764 - 16 Apr 2020
Cited by 1 | Viewed by 2238
Abstract
Since the great success of graphene, atomically thin layered nanomaterials—called two-dimensional (2D) materials—have attracted tremendous attention due to their extraordinary physical properties [...] Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)

Research

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9 pages, 11053 KiB  
Article
Artificial 2D van der Waals Synapse Devices via Interfacial Engineering for Neuromorphic Systems
by Woojin Park, Hye Yeon Jang, Jae Hyeon Nam, Jung-Dae Kwon, Byungjin Cho and Yonghun Kim
Nanomaterials 2020, 10(1), 88; https://doi.org/10.3390/nano10010088 - 02 Jan 2020
Cited by 11 | Viewed by 4017
Abstract
Despite extensive investigations of a wide variety of artificial synapse devices aimed at realizing a neuromorphic hardware system, the identification of a physical parameter that modulates synaptic plasticity is still required. In this context, a novel two-dimensional architecture consisting of a NbSe2 [...] Read more.
Despite extensive investigations of a wide variety of artificial synapse devices aimed at realizing a neuromorphic hardware system, the identification of a physical parameter that modulates synaptic plasticity is still required. In this context, a novel two-dimensional architecture consisting of a NbSe2/WSe2/Nb2O5 heterostructure placed on an SiO2/p+ Si substrate was designed to overcome the limitations of the conventional silicon-based complementary metal-oxide semiconductor technology. NbSe2, WSe2, and Nb2O5 were used as the metal electrode, active channel, and conductance-modulating layer, respectively. Interestingly, it was found that the post-synaptic current was successfully modulated by the thickness of the interlayer Nb2O5, with a thicker interlayer inducing a higher synapse spike current and a stronger interaction in the sequential pulse mode. Introduction of the Nb2O5 interlayer can facilitate the realization of reliable and controllable synaptic devices for brain-inspired integrated neuromorphic systems. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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12 pages, 3793 KiB  
Article
Reconfigurable Local Photoluminescence of Atomically-Thin Semiconductors via Ferroelectric-Assisted Effects
by Changhyun Ko
Nanomaterials 2019, 9(11), 1620; https://doi.org/10.3390/nano9111620 - 15 Nov 2019
Cited by 3 | Viewed by 2660
Abstract
Combining a pair of materials of different structural dimensions and functional properties into a hybrid material system may realize unprecedented multi-functional device applications. Especially, two-dimensional (2D) materials are suitable for being incorporated into the heterostructures due to their colossal area-to-volume ratio, excellent flexibility, [...] Read more.
Combining a pair of materials of different structural dimensions and functional properties into a hybrid material system may realize unprecedented multi-functional device applications. Especially, two-dimensional (2D) materials are suitable for being incorporated into the heterostructures due to their colossal area-to-volume ratio, excellent flexibility, and high sensitivity to interfacial and surface interactions. Semiconducting molybdenum disulfide (MoS2), one of the well-studied layered materials, has a direct band gap as one molecular layer and hence, is expected to be one of the promising key materials for next-generation optoelectronics. Here, using lateral 2D/3D heterostructures composed of MoS2 monolayers and nanoscale inorganic ferroelectric thin films, reversibly tunable photoluminescence has been demonstrated at the microscale to be over 200% upon ferroelectric polarization reversal by using nanoscale conductive atomic force microscopy tips. Also, significant ferroelectric-assisted modulation in electrical properties has been achieved from field-effect transistor devices based on the 2D/3D heterostructrues. Moreover, it was also shown that the MoS2 monolayer can be an effective electric field barrier in spite of its sub-nanometer thickness. These results would be of close relevance to exploring novel applications in the fields of optoelectronics and sensor technology. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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7 pages, 2610 KiB  
Article
Characteristics of p-Type Conduction in P-Doped MoS2 by Phosphorous Pentoxide during Chemical Vapor Deposition
by Jae Sang Lee, Chang-Soo Park, Tae Young Kim, Yoon Sok Kim and Eun Kyu Kim
Nanomaterials 2019, 9(9), 1278; https://doi.org/10.3390/nano9091278 - 07 Sep 2019
Cited by 26 | Viewed by 4156
Abstract
We demonstrated p-type conduction in MoS2 grown with phosphorous pentoxide via chemical vapor deposition (CVD). Monolayer MoS2 with a triangular shape and 15-µm grains was confirmed by atomic force microscopy. The difference between the Raman signals of the A1g and [...] Read more.
We demonstrated p-type conduction in MoS2 grown with phosphorous pentoxide via chemical vapor deposition (CVD). Monolayer MoS2 with a triangular shape and 15-µm grains was confirmed by atomic force microscopy. The difference between the Raman signals of the A1g and E12g modes for both the pristine and P-doped samples was 19.4 cm−1. In the X-ray photoelectron spectroscopy results, the main core level peaks of P-doped MoS2 downshifted by about 0.5 eV to a lower binding energy compared to the pristine material. Field-effect transistors (FETs) fabricated with the P-doped monolayer MoS2 showed p-type conduction with a field-effect mobility of 0.023 cm2/V⋅s and an on/off current ratio of 103, while FETs with the pristine MoS2 showed n-type behavior with a field-effect mobility of 29.7 cm2/V⋅s and an on/off current ratio of 105. The carriers in the FET channel were identified as holes with a concentration of 1.01 × 1011 cm−2 in P-doped MoS2, while the pristine material had an electron concentration of 6.47 × 1011 cm−2. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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9 pages, 1969 KiB  
Article
1.34 µm Q-Switched Nd:YVO4 Laser with a Reflective WS2 Saturable Absorber
by Taijin Wang, Yonggang Wang, Jiang Wang, Jing Bai, Guangying Li, Rui Lou and Guanghua Cheng
Nanomaterials 2019, 9(9), 1200; https://doi.org/10.3390/nano9091200 - 26 Aug 2019
Cited by 9 | Viewed by 3313
Abstract
In this work, a Tungsten disulfide (WS2) reflective saturable absorber (SA) fabricated using the Langmuir–Blodgett technique was used in a solid state Nd:YVO4 laser operating at 1.34 µm. A Q-switched laser was constructed. The shortest pulse width was 409 ns [...] Read more.
In this work, a Tungsten disulfide (WS2) reflective saturable absorber (SA) fabricated using the Langmuir–Blodgett technique was used in a solid state Nd:YVO4 laser operating at 1.34 µm. A Q-switched laser was constructed. The shortest pulse width was 409 ns with the repetition rate of 159 kHz, and the maximum output power was 338 mW. To the best of our knowledge, it is the first time that short laser pulses have been generated in a solid state laser at 1.34 µm using a reflective WS2 SA fabricated by the Langmuir–Blodgett method. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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9 pages, 1531 KiB  
Article
Improvement of the Bias Stress Stability in 2D MoS2 and WS2 Transistors with a TiO2 Interfacial Layer
by Woojin Park, Yusin Pak, Hye Yeon Jang, Jae Hyeon Nam, Tae Hyeon Kim, Seyoung Oh, Sung Mook Choi, Yonghun Kim and Byungjin Cho
Nanomaterials 2019, 9(8), 1155; https://doi.org/10.3390/nano9081155 - 12 Aug 2019
Cited by 11 | Viewed by 4171
Abstract
The fermi-level pinning phenomenon, which occurs at the metal–semiconductor interface, not only obstructs the achievement of high-performance field effect transistors (FETs) but also results in poor long-term stability. This paper reports on the improvement in gate-bias stress stability in two-dimensional (2D) transition metal [...] Read more.
The fermi-level pinning phenomenon, which occurs at the metal–semiconductor interface, not only obstructs the achievement of high-performance field effect transistors (FETs) but also results in poor long-term stability. This paper reports on the improvement in gate-bias stress stability in two-dimensional (2D) transition metal dichalcogenide (TMD) FETs with a titanium dioxide (TiO2) interfacial layer inserted between the 2D TMDs (MoS2 or WS2) and metal electrodes. Compared to the control MoS2, the device without the TiO2 layer, the TiO2 interfacial layer deposited on 2D TMDs could lead to more effective carrier modulation by simply changing the contact metal, thereby improving the performance of the Schottky-barrier-modulated FET device. The TiO2 layer could also suppress the Fermi-level pinning phenomenon usually fixed to the metal–semiconductor interface, resulting in an improvement in transistor performance. Especially, the introduction of the TiO2 layer contributed to achieving stable device performance. Threshold voltage variation of MoS2 and WS2 FETs with the TiO2 interfacial layer was ~2 V and ~3.6 V, respectively. The theoretical result of the density function theory validated that mid-gap energy states created within the bandgap of 2D MoS2 can cause a doping effect. The simple approach of introducing a thin interfacial oxide layer offers a promising way toward the implementation of high-performance 2D TMD-based logic circuits. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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10 pages, 19800 KiB  
Article
Preparation and Tribological Properties of WS2 Hexagonal Nanoplates and Nanoflowers
by Xianghua Zhang, Jiangtao Wang, Hongxiang Xu, Heng Tan and Xia Ye
Nanomaterials 2019, 9(6), 840; https://doi.org/10.3390/nano9060840 - 01 Jun 2019
Cited by 24 | Viewed by 5307
Abstract
This paper presents the facile synthesis of two different morphologies of WS2 nanomaterials—WS2 hexagonal nanoplates and nanoflowers—by a sulfurization reaction. The phases and morphology of the samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy [...] Read more.
This paper presents the facile synthesis of two different morphologies of WS2 nanomaterials—WS2 hexagonal nanoplates and nanoflowers—by a sulfurization reaction. The phases and morphology of the samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The tribological performance of the two kinds of WS2 nanomaterials as additives in paraffin oil were measured using a UMT (Universal Mechanical Tester)-2 tribotester. The results demonstrated that the friction and wear performance of paraffin oil can be greatly improved with the addition of WS2 nanomaterials, and that the morphology and content of WS2 nanomaterials have a significant effect on the tribological properties of paraffin oil. The tribological performance of lubricating oil was best when the concentration of the WS2 nanomaterial additive was 0.5 wt %. Moreover, the paraffin oil with added WS2 nanoflowers exhibited better tribological properties than paraffin oil with added WS2 hexagonal nanoplates. The superior tribological properties of WS2 nanoflowers can be attributed to their special morphology, which contributes to the formation of a uniform tribo-film during the sliding process. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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10 pages, 3194 KiB  
Article
Interlayer Difference of Bilayer-Stacked MoS2 Structure: Probing by Photoluminescence and Raman Spectroscopy
by Xiangzhe Zhang, Renyan Zhang, Xiaoming Zheng, Yi Zhang, Xueao Zhang, Chuyun Deng, Shiqiao Qin and Hang Yang
Nanomaterials 2019, 9(5), 796; https://doi.org/10.3390/nano9050796 - 24 May 2019
Cited by 9 | Viewed by 4461
Abstract
This work reports the interlayer difference of exciton and phonon performance between the top and bottom layer of a bilayer-stacked two-dimensional materials structure (BSS). Through photoluminescence (PL) and Raman spectroscopy, we find that, compared to that of the bottom layer, the top layer [...] Read more.
This work reports the interlayer difference of exciton and phonon performance between the top and bottom layer of a bilayer-stacked two-dimensional materials structure (BSS). Through photoluminescence (PL) and Raman spectroscopy, we find that, compared to that of the bottom layer, the top layer of BSS demonstrates PL redshift, Raman E 2 g 1 mode redshift, and lower PL intensity. Spatial inhomogeneity of PL and Raman are also observed in the BSS. Based on theoretical analysis, these exotic effects can be attributed to substrate-coupling-induced strain and doping. Our findings provide pertinent insight into film–substrate interaction, and are of great significance to researches on bilayer-stacked structures including twisted bilayer structure, Van der Waals hetero- and homo-structure. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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8 pages, 3440 KiB  
Article
Direct Observation of Raman Spectra in Black Phosphorus under Uniaxial Strain Conditions
by Stacy Liang, Md Nazmul Hasan and Jung-Hun Seo
Nanomaterials 2019, 9(4), 566; https://doi.org/10.3390/nano9040566 - 08 Apr 2019
Cited by 24 | Viewed by 5597
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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12 pages, 25599 KiB  
Article
Direct Exfoliation of Natural SiO2-Containing Molybdenite in Isopropanol: A Cost Efficient Solution for Large-Scale Production of MoS2 Nanosheetes
by Wenyan Zhao, Tao Jiang, Yujie Shan, Hongrui Ding, Junxian Shi, Haibin Chu and Anhuai Lu
Nanomaterials 2018, 8(10), 843; https://doi.org/10.3390/nano8100843 - 17 Oct 2018
Cited by 10 | Viewed by 4361
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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7 pages, 1450 KiB  
Article
Operation Mechanism of a MoS2/BP Heterojunction FET
by Sung Kwan Lim, Soo Cheol Kang, Tae Jin Yoo, Sang Kyung Lee, Hyeon Jun Hwang and Byoung Hun Lee
Nanomaterials 2018, 8(10), 797; https://doi.org/10.3390/nano8100797 - 07 Oct 2018
Cited by 11 | Viewed by 4333
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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8 pages, 2316 KiB  
Communication
Exfoliation and Characterization of V2Se9 Atomic Crystals
by Bum Jun Kim, Byung Joo Jeong, Seungbae OH, Sudong Chae, Kyung Hwan Choi, Tuqeer Nasir, Sang Hoon Lee, Kwan-Woo Kim, Hyung Kyu Lim, Ik Jun Choi, Ji-Yun Moon, Hak Ki Yu, Jae-Hyun Lee and Jae-Young Choi
Nanomaterials 2018, 8(9), 737; https://doi.org/10.3390/nano8090737 - 18 Sep 2018
Cited by 25 | Viewed by 4496
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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12 pages, 46033 KiB  
Article
Feasible Route for a Large Area Few-Layer MoS2 with Magnetron Sputtering
by Wei Zhong, Sunbin Deng, Kai Wang, Guijun Li, Guoyuan Li, Rongsheng Chen and Hoi-Sing Kwok
Nanomaterials 2018, 8(8), 590; https://doi.org/10.3390/nano8080590 - 03 Aug 2018
Cited by 30 | Viewed by 6477
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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9 pages, 4998 KiB  
Article
α-MoO3 Crystals with a Multilayer Stack Structure Obtained by Annealing from a Lamellar MoS2/g-C3N4 Nanohybrid
by Pablo Martín-Ramos, Ignacio A. Fernández-Coppel, Manuel Avella and Jesús Martín-Gil
Nanomaterials 2018, 8(7), 559; https://doi.org/10.3390/nano8070559 - 22 Jul 2018
Cited by 16 | Viewed by 5682
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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