Handbook of Graphene, Volume 3

Graphene-like 2D Materials

Mei Zhang

• Publisher: Wiley-Scrivener
• Year: 2019
• Print ISBN:
  9781119469650
• Edition: 1
• eBook ISBN:
  9781119469674
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

The third volume in a series of handbooks on graphene research and applications

Graphene is a valuable nanomaterial used in technology. This handbook is focused on Graphene-Like 2D Materials. The Handbook of Graphene, Volume 3 covers topics that include planar graphene superlattices; magnetic and optical properties of graphene materials with porous defects; and nanoelectronic application of graphyne and its structural derivatives.

Chapter 1
Proximity-Induced Topological Transition and Strain-Induced Charge Transfer in Graphene/MoS₂ Bilayer Heterostructures

Sobhit Singh¹*, Abdulrhman M. Alsharari², Sergio E. Ulloa² and Aldo H. Romero¹

¹Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia, USA

²Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio, USA

^*Corresponding author: [email protected]

Abstract

Graphene/MoS₂ heterostructures are formed by combining the nanosheets of graphene and monolayer MoS₂. The electronic features of both constituent monolayers are rather well preserved in the resultant heterostructure due to the weak van der Waals interaction between the layers. However, the proximity of MoS₂ induces strong spin orbit coupling effect of strength ~1 meV in graphene, which is nearly three orders of magnitude larger than the intrinsic spin orbit coupling of pristine graphene. This opens a bandgap in graphene and further causes anti-crossings of the spin-nondegenerate bands near the Dirac point. Lattice incommensurate graphene/MoS₂ heterostructure exhibits interesting moiré patterns which have been observed in experiments. The electronic bandstructure of heterostructure is very sensitive to biaxial strain and interlayer twist. Although the Dirac cone of graphene remains intact and no charge-transfer between graphene and MoS₂ layers occurs at ambient conditions, a strain-induced charge-transfer can be realized in graphene/MoS₂ heterostructure. Application of a gate voltage reveals the occurrence of a topological phase transition in graphene/MoS₂ heterostructure. In this chapter, we discuss the crystal structure, interlayer effects, electronic structure, spin states, and effects due to strain and substrate proximity on the electronic properties of graphene/MoS₂ heterostructure. We further present an overview of the distinct topological quantum phases of graphene/MoS₂ heterostructure and review the recent advancements in this field.

Keywords: Heterostructure, graphene, transition metal dichalcogenide, charge transfer, Dirac point, tight binding model, topological phase transition, spin-orbit coupling, proximity effects, Berry curvature

1.1 Introduction

The successful isolation of graphene from bulk graphite [1] has triggered a new burgeoning research area in atomically thin two-dimensional (2D) materials. Since the last decade, several 2D materials namely – graphene, BN, MoS₂, MoSe₂, WS₂, WSe₂, MoTe₂, Xene sheets (X = Si, Ge, Sn), phosphorene, bismuthene, and many more, have been fabricated and extensively investigated due to their promising applications in the electronic, valleytronic, spintronic, catalysis, energy, and biosensing areas [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]. Some of the notable properties that make 2D materials interesting are: high carrier mobility, superconductivity, mechanical flexibility, exceptional thermal conductivity, large photoluminescence, high optical and UV absorption, quantum spin Hall effect, strong light–matter interactions, and observation of highly confined plasmon–polaritons [2, 14, 15, 16]. Interestingly, these properties can be efficiently harnessed in 2D materials by means of strain engineering, number of atomic layers, adsorption, intercalation, interlayer twist, proximity effects, and gate voltage [17, 18, 19, 20]. Furthermore, several types of 2D materials can be vertically stacked to design van der Waals (vdW) heterostructures, which often enhance the desirable properties of the constituent atomic layers [17, 18, 19, 21]. These heterostructures offer unique ways to tailor their remarkable properties, hence they have promising applications in modern technology. However, control of the doping type, carrier concentration, and stoichiometry remains challenging in most of the known 2D materials and vdW heterostructures [21].

Graphene, a two dimensional monolayer of carbon atoms arranged in a honeycomb lattice, has emerged as the most celebrated 2D material of the last decade. It has been thoroughly investigated and many of its interesting features have been revealed [2]. A single layer graphene exhibits numerous novel features such as ultra-high intrinsic mobility (200,000 cm²/V⁻¹s⁻¹), large electrical conductivity, excellent thermal conductivity (5,000 W⁻¹K⁻¹), biosensing, and exceptional elastic and mechanical properties with a very large Young’s modulus (~1.0 TPa) [2, 22, 23]. However, the negligible intrinsic spin–orbit coupling (SOC) and correspondingly small energy bandgap limit many practical applications of pristine graphene in spintronics. In recent years, researchers have succeeded in enhancing the bandgap of graphene by several orders using unconventional methods and substrate proximity effects. The availability of many other 2D crystals allows us to design new graphene-based vdW heterostructures having strong proximity effects. A particular family of such 2D crystals is the semiconducting transition metal dichalcogenides (TMDs)-MX₂ (M = Mo, W and X = S, Se, Te) – that shows interesting optoelectronic and valleytronic features, and offer strong proximity effects on graphene’s electronic bandstructure [24, 25, 26, 27, 28].

Atomically thin MX₂ semiconductors (M = W, Mo an...

Table of contents

• Cover
• Title Page
• Copyright
• Preface
• Chapter 1: Proximity-Induced Topological Transition and Strain-Induced Charge Transfer in Graphene/MoS2 Bilayer Heterostructures
• Chapter 2: Planar Graphene Superlattices
• Chapter 3: Magnetic and Optical Properties of Graphene Materials with Porous Defects
• Chapter 4: Graphynes: Advanced Carbon Materials with Layered Structure
• Chapter 5: Nanoelectronic Application of Graphyne and Its Structural Derivatives
• Chapter 6: Twisted Bilayer Graphene: Low-Energy Physics, Electronic and Optical Properties
• Chapter 7: Effects of Charged Coulomb Impurities on Low-Lying Energy Spectra in Graphene Magnetic Dot and Ring
• Chapter 8: Graphene in Bioelectronics
• Chapter 9: Graphene Metamaterial Electron Optics: Excitation Processes and Electro-Optical Modulation
• Chapter 10: Linear Carbon: From 1D Carbyne to 2D Hybrid sp-sp2 Nanostructures Beyond Graphene
• Chapter 11: Band Structure Modifications in Beyond Graphene Materials
• Chapter 12: Chemically Modified 2D Materials: Production and Applications
• Chapter 13: Black Phosphorus Saturable Absorber for Passive Mode-Locking Pulses Generation
• Chapter 14: Search for Fundamental Physics on Table Top Experiments with Dirac–Weyl Materials
• Index
• End User License Agreement