Two-Dimensional Materials beyond Graphene and their Van der Waals Heterostructures

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: closed (31 July 2017) | Viewed by 117777

Special Issue Editors

National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, UK
Interests: electronic and optical properties of 2D materials and heterostructures; graphene; scanning probe microscopy; electronic effects in photoexcited materials; surface processes in various environments; nano- and opto-electronic applications of graphene and 2D materials
Foundation for Research and Technology Hellas-Institute of Chemical Engineering Sciences (FORTH/ICE-HT), GR-26504 Rio-Patras, Greece
Interests: laser-assisted growth of graphene; 2D TMDCs materials and applications; ZnO-based nanomaterials, gas sensing, and photocatalysis for water disinfection; amorphous semiconductors
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Special Issue Information

Dear Colleagues,

Recently-isolated two-dimensional (2D) atomic crystals provide an attractive material platform for exploring the fundamentals of atomically thin semiconductors, as well as presenting exciting prospects for future advances in fields as diverse as sensors and catalysis, membranes, energy storage/conversion, optoelectronics, spintronics, and valleytronics.

The realm of properties and applications is further enriched by artificially integrating 2D monolayers in vertical and lateral heterostructures, which enable the engineering of novel architectures with a rich combination of properties for multifunctional systems with enhanced performance. Given the astonishing developments in the field, this Special Issue will be dedicated to discussing the very latest research associated with 2D materials and their heterostructures, from fundamentals to applications, and addressing an outlook for emerging advances of the field.

Contributions are invited on 2D materials research-related topics, with special emphasis on (but not limited to):

  • Controlled synthesis of 2D materials (including transition metal dichalcogenides, phosphorene, silicene, germanene, stanene) and heterostructures

  • Advanced characterisation of electronic, optical, mechanical and catalytic properties

  • Surface chemistry and chemical functionalisation of 2D materials, including doping and defect engineering

  • Emerging applications in optoelectronics, spintronics, valleytronics, photonics, energy harvesting and storage, catalysis, sensors,

  • Modelling of properties and devices based on 2D materials and heterostructures

Dr. Cristina E. Giusca
Dr. Spyros Yannopoulos
Guest Editors

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Keywords

  • 2D materials

  • heterostructures

  • layered crystals

  • 2D heterojunction

  • transition metal dichalcogenides

  • monolayer

  • 2D semiconductors

  • van der Waals epitaxy

  • 2D-material based devices

  • technological applications

Published Papers (11 papers)

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Research

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4317 KiB  
Article
Algebraic Theory of Crystal Vibrations: Localization Properties of Wave Functions in Two-Dimensional Lattices
by Barbara Dietz, Francesco Iachello and Michal Macek
Crystals 2017, 7(8), 246; https://doi.org/10.3390/cryst7080246 - 07 Aug 2017
Cited by 14 | Viewed by 5619
Abstract
The localization properties of the wave functions of vibrations in two-dimensional (2D) crystals are studied numerically for square and hexagonal lattices within the framework of an algebraic model. The wave functions of 2D lattices have remarkable localization properties, especially at the van Hove [...] Read more.
The localization properties of the wave functions of vibrations in two-dimensional (2D) crystals are studied numerically for square and hexagonal lattices within the framework of an algebraic model. The wave functions of 2D lattices have remarkable localization properties, especially at the van Hove singularities (vHs). Finite-size sheets with a hexagonal lattice (graphene-like materials), in addition, exhibit at zero energy a localization of the wave functions at zigzag edges, so-called edge states. The striped structure of the wave functions at a vHs is particularly noteworthy. We have investigated its stability and that of the edge states with respect to perturbations in the lattice structure, and the effect of the boundary shape on the localization properties. We find that the stripes disappear instantaneously at the vHs in a square lattice when turning on the perturbation, whereas they broaden but persist at the vHss in a hexagonal lattice. For one of them, they eventually merge into edge states with increasing coupling, which, in contrast to the zero-energy edge states, are localized at armchair edges. The results are corroborated based on participation ratios, obtained under various conditions. Full article
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2148 KiB  
Article
Graphene-Hexagonal Boron Nitride Heterostructure as a Tunable Phonon–Plasmon Coupling System
by Sheng Qu, Hongxia Liu, Lu Dong, Lei Wu, Congcong Ma and Shulong Wang
Crystals 2017, 7(2), 49; https://doi.org/10.3390/cryst7020049 - 10 Feb 2017
Cited by 12 | Viewed by 6375
Abstract
The layered van der Waals (vdW) heterostructure, assembled from monolayer graphene, hexagonal boron nitride (h-BN) and other atomic crystals in various combinations, is emerging as a new paradigm with which to attain desired electronic and optical properties. In this paper, we study theoretically [...] Read more.
The layered van der Waals (vdW) heterostructure, assembled from monolayer graphene, hexagonal boron nitride (h-BN) and other atomic crystals in various combinations, is emerging as a new paradigm with which to attain desired electronic and optical properties. In this paper, we study theoretically the mid-infrared optical properties of the vdW heterostructure based on the graphene–h-BN system. The light–matter interaction of this heterostructure system is described by the hyperbolic phonon–plasmon polaritons which originate from the coupling modes of surface plasmon polaritons (SPPs) in graphene with hyperbolic phonon polaritons (HPPs) in h-BN. By numerical simulation, we find that the coupling modes are governed by the Fermi level of monolayer graphene, the thickness of the h-BN slab and the mode excitation sequence of SPPs and HPPs. Moreover, the response of the coupling modes of the graphene–h-BN heterostructure on a noble metal layer is also proposed in this paper. Full article
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4597 KiB  
Article
The Effect of Twin Grain Boundary Tuned by Temperature on the Electrical Transport Properties of Monolayer MoS2
by Luojun Du, Hua Yu, Li Xie, Shuang Wu, Shuopei Wang, Xiaobo Lu, Mengzhou Liao, Jianling Meng, Jing Zhao, Jing Zhang, Jianqi Zhu, Peng Chen, Guole Wang, Rong Yang, Dongxia Shi and Guangyu Zhang
Crystals 2016, 6(9), 115; https://doi.org/10.3390/cryst6090115 - 14 Sep 2016
Cited by 19 | Viewed by 7891
Abstract
Theoretical calculation and experimental measurement have shown that twin grain boundary (GB) of molybdenum disulphide (MoS2) exhibits extraordinary effects on transport properties. Precise transport measurements need to verify the transport mechanism of twin GB in MoS2. Here, monolayer molybdenum [...] Read more.
Theoretical calculation and experimental measurement have shown that twin grain boundary (GB) of molybdenum disulphide (MoS2) exhibits extraordinary effects on transport properties. Precise transport measurements need to verify the transport mechanism of twin GB in MoS2. Here, monolayer molybdenum disulphide with a twin grain boundary was grown in our developed low-pressure chemical vapor deposition (CVD) system, and we investigated how the twin GB affects the electrical transport properties of MoS2 by temperature-dependent transport studies. At low temperature, the twin GB can increase the in-plane electrical conductivity of MoS2 and the transport exhibits variable-range hopping (VRH), while at high temperature, the twin GB impedes the electrical transport of MoS2 and the transport exhibits nearest-neighbor hopping (NNH). Our results elucidate carrier transport mechanism of twin GB and give an important indication of twin GB in tailoring the electronic properties of MoS2 for its applications in next-generation electronics and optoelectronic devices. Full article
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Review

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17 pages, 5696 KiB  
Review
Production Methods of Van der Waals Heterostructures Based on Transition Metal Dichalcogenides
by Haimei Qi, Lina Wang, Jie Sun, Yi Long, Peng Hu, Fucai Liu and Xuexia He
Crystals 2018, 8(1), 35; https://doi.org/10.3390/cryst8010035 - 15 Jan 2018
Cited by 45 | Viewed by 12769
Abstract
Two dimensional (2D) materials have gained significant attention since the discovery of graphene in 2004. Layered transition metal dichalcogenides (TMDs) have become the focus of 2D materials in recent years due to their wide range of chemical compositions and a variety of properties. [...] Read more.
Two dimensional (2D) materials have gained significant attention since the discovery of graphene in 2004. Layered transition metal dichalcogenides (TMDs) have become the focus of 2D materials in recent years due to their wide range of chemical compositions and a variety of properties. These TMDs layers can be artificially integrated with other layered materials into a monolayer (lateral) or a multilayer stack (vertical) heterostructures. The resulting heterostructures provide new properties and applications beyond their component 2D atomic crystals and many exciting experimental results have been reported during the past few years. In this review, we present the various synthesis methods (mechanical exfoliation, physical vapor transport, chemical vapor deposition, and molecular beam epitaxy method) on van der Waals heterostructures based on different TMDs as well as an outlook for future research. Full article
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21 pages, 3979 KiB  
Review
Introducing Magnetism into 2D Nonmagnetic Inorganic Layered Crystals: A Brief Review from First-Principles Aspects
by Xinying Shi, Zhongjia Huang, Marko Huttula, Taohai Li, Suya Li, Xiao Wang, Youhua Luo, Meng Zhang and Wei Cao
Crystals 2018, 8(1), 24; https://doi.org/10.3390/cryst8010024 - 07 Jan 2018
Cited by 17 | Viewed by 6723
Abstract
Pioneering explorations of the two-dimensional (2D) inorganic layered crystals (ILCs) in electronics have boosted low-dimensional materials research beyond the prototypical but semi-metallic graphene. Thanks to species variety and compositional richness, ILCs are further activated as hosting matrices to reach intrinsic magnetism due to [...] Read more.
Pioneering explorations of the two-dimensional (2D) inorganic layered crystals (ILCs) in electronics have boosted low-dimensional materials research beyond the prototypical but semi-metallic graphene. Thanks to species variety and compositional richness, ILCs are further activated as hosting matrices to reach intrinsic magnetism due to their semiconductive natures. Herein, we briefly review the latest progresses of manipulation strategies that introduce magnetism into the nonmagnetic 2D and quasi-2D ILCs from the first-principles computational perspectives. The matrices are concerned within naturally occurring species such as MoS2, MoSe2, WS2, BN, and synthetic monolayers such as ZnO and g-C2N. Greater attention is spent on nondestructive routes through magnetic dopant adsorption; defect engineering; and a combination of doping-absorbing methods. Along with structural stability and electric uniqueness from hosts, tailored magnetic properties are successfully introduced to low-dimensional ILCs. Different from the three-dimensional (3D) bulk or zero-dimensional (0D) cluster cases, origins of magnetism in the 2D space move past most conventional physical models. Besides magnetic interactions, geometric symmetry contributes a non-negligible impact on the magnetic properties of ILCs, and surprisingly leads to broken symmetry for magnetism. At the end of the review, we also propose possible combination routes to create 2D ILC magnetic semiconductors, tentative theoretical models based on topology for mechanical interpretations, and next-step first-principles research within the domain. Full article
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8448 KiB  
Review
Recent Advances in Two-Dimensional Materials with Charge Density Waves: Synthesis, Characterization and Applications
by Mongur Hossain, Zhaoyang Zhao, Wen Wen, Xinsheng Wang, Juanxia Wu and Liming Xie
Crystals 2017, 7(10), 298; https://doi.org/10.3390/cryst7100298 - 03 Oct 2017
Cited by 44 | Viewed by 19409
Abstract
Recently, two-dimensional (2D) charge density wave (CDW) materials have attracted extensive interest due to potential applications as high performance functional nanomaterials. As other 2D materials, 2D CDW materials are layered materials with strong in-plane bonding and weak out-of-plane interactions enabling exfoliation into layers [...] Read more.
Recently, two-dimensional (2D) charge density wave (CDW) materials have attracted extensive interest due to potential applications as high performance functional nanomaterials. As other 2D materials, 2D CDW materials are layered materials with strong in-plane bonding and weak out-of-plane interactions enabling exfoliation into layers of single unit cell thickness. Although bulk CDW materials have been studied for decades, recent developments in nanoscale characterization and device fabrication have opened up new opportunities allowing applications such as oscillators, electrodes in supercapacitors, energy storage and conversion, sensors and spinelectronic devices. In this review, we first outline the synthesis techniques of 2D CDW materials including mechanical exfoliation, liquid exfoliation, chemical vapor transport (CVT), chemical vapor deposition (CVD), molecular beam epitaxy (MBE) and electrochemical exfoliation. Then, the characterization procedure of the 2D CDW materials such as temperature-dependent Raman spectroscopy, temperature-dependent resistivity, magnetic susceptibility and scanning tunneling microscopy (STM) are reviewed. Finally, applications of 2D CDW materials are reviewed. Full article
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5853 KiB  
Review
Interfacing 2D Semiconductors with Functional Oxides: Fundamentals, Properties, and Applications
by Zhiquan Yuan, Jiwei Hou and Kai Liu
Crystals 2017, 7(9), 265; https://doi.org/10.3390/cryst7090265 - 31 Aug 2017
Cited by 18 | Viewed by 8905
Abstract
Two-dimensional semiconductors, such as transition-metal dichalcogenides (TMDs) and black phosphorous (BP), have found various potential applications in electronic and opto-electronic devices. However, several problems including low carrier mobility and low photoluminescence efficiencies still limit the performance of these devices. Interfacing 2D semiconductors with [...] Read more.
Two-dimensional semiconductors, such as transition-metal dichalcogenides (TMDs) and black phosphorous (BP), have found various potential applications in electronic and opto-electronic devices. However, several problems including low carrier mobility and low photoluminescence efficiencies still limit the performance of these devices. Interfacing 2D semiconductors with functional oxides provides a way to address the problems by overcoming the intrinsic limitations of 2D semiconductors and offering them multiple functionalities with various mechanisms. In this review, we first focus on the physical effects of various types of functional oxides on 2D semiconductors, mostly on MoS2 and BP as they are the intensively studied 2D semiconductors. Insulating, semiconducting, conventional piezoelectric, strongly correlated, and magnetic oxides are discussed. Then we introduce the applications of these 2D semiconductors/functional oxides systems in field-effect devices, nonvolatile memory, and photosensing. Finally, we discuss the perspectives and challenges within this research field. Our review provides a comprehensive understanding of 2D semiconductors/functional oxide heterostructures, and could inspire novel ideas in interface engineering to improve the performance of 2D semiconductor devices. Full article
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5701 KiB  
Review
Material and Device Architecture Engineering Toward High Performance Two-Dimensional (2D) Photodetectors
by Qiuhong Cui, Yijun Yang, Junmeng Li, Feng Teng and Xi Wang
Crystals 2017, 7(5), 149; https://doi.org/10.3390/cryst7050149 - 22 May 2017
Cited by 22 | Viewed by 7502
Abstract
Photodetectors based on two-dimensional (2D) nanostructures have led to a high optical response, and a long photocarrier lifetime because of spatial confinement effects. Since the discovery of graphene, many different 2D semiconductors have been developed and utilized in the ultrafast and ultrasensitive detection [...] Read more.
Photodetectors based on two-dimensional (2D) nanostructures have led to a high optical response, and a long photocarrier lifetime because of spatial confinement effects. Since the discovery of graphene, many different 2D semiconductors have been developed and utilized in the ultrafast and ultrasensitive detection of light in the ultraviolet, visible, infrared and terahertz frequency ranges. This review presents a comprehensive summary of recent breakthroughs in constructing high-performance photodetectors based on 2D materials. First, we give a general overview of 2D photodetectors based on various single-component materials and their operating wavelength (ultraviolet to terahertz regime). Then, we summarize the design and controllable synthesis of heterostructure material systems to promote device photoresponse. Subsequently, special emphasis is put on the accepted methods in rational engineering of device architectures toward the photoresponse improvements. Finally, we conclude with our personal viewpoints on the challenges and promising future directions in this research field. Full article
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1054 KiB  
Review
Dirac Cones in Graphene, Interlayer Interaction in Layered Materials, and the Band Gap in MoS2
by Ivan N. Yakovkin
Crystals 2016, 6(11), 143; https://doi.org/10.3390/cryst6110143 - 10 Nov 2016
Cited by 39 | Viewed by 15455
Abstract
The 2D outlook of graphene and similar layers has initiated a number of theoretical considerations of electronic structure that are both interesting and exciting, but applying these ideas to real layered systems, in terms of a model 2D system, must be done with [...] Read more.
The 2D outlook of graphene and similar layers has initiated a number of theoretical considerations of electronic structure that are both interesting and exciting, but applying these ideas to real layered systems, in terms of a model 2D system, must be done with extreme care. In the present review, we will discuss the applicability of the 2D concept with examples of peculiarities of electronic structures and interactions in particular layered systems: (i) Dirac points and cones in graphene; (ii) van der Waals interaction between MoS2 monolayers; and (iii) the issue of a 2D screening in estimates of the band gap for MoS2 monolayers. Full article
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5821 KiB  
Review
Van Der Waals Heterostructures between Small Organic Molecules and Layered Substrates
by Han Huang, Yingbao Huang, Shitan Wang, Menglong Zhu, Haipeng Xie, Lei Zhang, Xiaoming Zheng, Qiliang Xie, Dongmei Niu and Yongli Gao
Crystals 2016, 6(9), 113; https://doi.org/10.3390/cryst6090113 - 09 Sep 2016
Cited by 24 | Viewed by 10513
Abstract
Two dimensional atomic crystals, like grapheme (G) and molybdenum disulfide (MoS2), exhibit great interest in electronic and optoelectronic applications. The excellent physical properties, such as transparency, semiconductivity, and flexibility, make them compatible with current organic electronics. Here, we review recent progress [...] Read more.
Two dimensional atomic crystals, like grapheme (G) and molybdenum disulfide (MoS2), exhibit great interest in electronic and optoelectronic applications. The excellent physical properties, such as transparency, semiconductivity, and flexibility, make them compatible with current organic electronics. Here, we review recent progress in the understanding of the interfaces of van der Waals (vdW) heterostructures between small organic molecules (pentacene, copper phthalocyanine (CuPc), perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), and dioctylbenzothienobenzothiophene (C8-BTBT)) and layered substrates (G, MoS2 and hexagonal boron nitride (h-BN)). The influences of the underlying layered substrates on the molecular arrangement, electronic and vibrational properties will be addressed. Full article
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9847 KiB  
Review
Graphene-Like ZnO: A Mini Review
by Huy Q. Ta, Liang Zhao, Darius Pohl, Jinbo Pang, Barbara Trzebicka, Bernd Rellinghaus, Didier Pribat, Thomas Gemming, Zhongfan Liu, Alicja Bachmatiuk and Mark H. Rümmeli
Crystals 2016, 6(8), 100; https://doi.org/10.3390/cryst6080100 - 22 Aug 2016
Cited by 86 | Viewed by 14797
Abstract
The isolation of a single layer of graphite, known today as graphene, not only demonstrated amazing new properties but also paved the way for a new class of materials often referred to as two-dimensional (2D) materials. Beyond graphene, other 2D materials include h-BN, [...] Read more.
The isolation of a single layer of graphite, known today as graphene, not only demonstrated amazing new properties but also paved the way for a new class of materials often referred to as two-dimensional (2D) materials. Beyond graphene, other 2D materials include h-BN, transition metal dichalcogenides (TMDs), silicene, and germanene, to name a few. All tend to have exciting physical and chemical properties which appear due to dimensionality effects and modulation of their band structure. A more recent member of the 2D family is graphene-like zinc oxide (g-ZnO) which also holds great promise as a future functional material. This review examines current progress in the synthesis and characterization of g-ZnO. In addition, an overview of works dealing with the properties of g-ZnO both in its pristine form and modified forms (e.g., nano-ribbon, doped material, etc.) is presented. Finally, discussions/studies on the potential applications of g-ZnO are reviewed and discussed. Full article
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