2D Nanoscale Heterostructured Materials

Synthesis, Properties, and Applications

Satyabrata Jit, Santanu Das

• Publisher: Elsevier
• Year: 2020
• Print ISBN:
  9780128176788
• eBook ISBN:
  9780128176795
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

2D Nanoscale Heterostructured Materials: Synthesis, Properties, and Applications assesses the current status and future prospects for 2D materials other than graphene (e.g., BN nanosheets, MoS2, NbSe2, WS2, etc.) that have already been contemplated for both low-end and high-end technological applications. The book offers an overview of the different synthesis techniques for 2D materials and their heterostructures, with a detailed explanation of the many potential future applications. It provides an informed overview and fundamentals properties related to the 2D Transition metal dichalcogenide materials and their heterostructures. The book helps researchers to understand the progress of this field and points the way to future research in this area. - Explores synthesis techniques of newly evolved 2D materials and their heterostructures with controlled properties - Offers detailed analysis of the fundamental properties (via various experimental process and simulations techniques) of 2D heterostructures materials - Discusses the applications of 2D heterostructured materials in various high-performance devices

1

Discovery and characterization of 2D materials and their heterostructures

Kamal Choudhary and Francesca Tavazza, Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD, United States

Abstract

We introduce a simple criterion to identify two-dimensional (2D) materials based on the comparison between experimental lattice constants and lattice constants mainly, obtained from density functional theory (DFT) calculation to systematically discover 2D materials. Specifically, if the relative difference between the two lattice constants for a specific material is greater than or equal to 5%, we predict them to be good candidates for 2D materials. We have predicted at least 1356 such 2D materials. In addition to the lattice constant criteria, we show the usefulness of data-mining approaches to discover 2D materials. To validate our criterion, we calculated the exfoliation energy of the suggested layered materials, and we found that in 88.9% of the cases the currently accepted criterion for exfoliation was satisfied. For all the systems satisfying our criterion, we manually create single layer systems and calculate their energetics, structural, electronic, vibrational, and elastic properties for both the bulk and the single layer cases. Additionally, we examine the cases where combing the predicted 2D materials are possible for heterostructures based on strain due to lattice mismatch. For all the systems where strains are reasonably less, we predict the properties of the heterostructures.

Keywords

2D materials; exfoliation; heterostructures; characterization; discovery of 2D materials

1.1 Introduction

Bonding in solids can be primarily of four types: metallic, covalent, ionic and vdW bonding [1]. Often a material has only one type of bonding, say Silicon with covalent bonding. However, two-dimensional (2D) materials (like graphene, black phosphorous, and MoS₂, Fig. 1–1) are characterized by intralayer covalent and interlayer vdW bonding [2]. The 2D materials have many interesting/technologically applicable properties, that are often different from their 3D counterpart. For instance, due to quantum confinement effects, often bang gaps increase going from bulk to ML, and even transform from “indirect” to “direct” (2H-MoS₂) allowing enhanced tunability [3]. Due to the absence of dangling bonds on the 2D surfaces, 2D materials can exist in free-standing monolater atomic forms unlike conventional semiconductors (silicon) allowing the development of miniatured electronic devices [4]. The 2D materials cover a wide variety of chemistry and bandgaps. For instance, graphene is semimetallic, 1T′-MoTe₂ metallic, 2H-MoS₂ semiconducting and h-BN insulating in nature. Furthermore, the 2D materials can be ferromagnetic [5] and host topologically nontrivial bands [6]. Examples of a few commonly known 2D materials are shown in Fig. 1–1. Most importantly, the absence of dangling bonds allows the integration of highly disparate materials without stringent lattice matching criteria [4]. This enables immense freedom to integrate 2D materials to create vdW heterostructures. The creation of vdW heterostructures allows the creation of extraordinary devices including broadband photodetectors with ultrahigh gain, generation of new transistors with unprecedented speed and flexibility.

Figure 1–1 Bandgap trends in 2D materials. Bandgaps vary in a wide range for 2D materials, for example: 1T′-MoTe₂ is metallic, graphene is semi-metallic, Black-P, 2H-MoS₂, SnS (buckled and puckered phases) are semiconducting, and h-BN, AlClO are insulating: (A) graphene; (B) 1T′-MoTe₂; (C) black-P; (D) 2H-MoS2; (E) puckered SnS; (F) buckled SnS; (G) hexagonal BN; and (H) AlClO.

In fact, 2D materials belong to a special class of low-dimensional materials with vdW bonding primarily in one crystallographic direction. The low-dimensional materials can also be 1D and 0D in nature characterized by the presence of vdW bonding in two and three crystallographic directions respectively as shown in Fig. 1–2.

Figure 1–2 Figure showing different classes of materials, for example: (A) 3D-bulk diamond Si, (B) 2D-bulk 2H-MoS₂, (C) 1D-bulk MoBr₃, (D) 0D-bulk BiI₃. Dimensionality is reduced due to the presence of vdW bonding in one, two, or three crystallographic dimensions.

In addition to 2D–2D vdW heterostructures, there has been recent research [7] on 2D–1D and 2D–0D vdW heterostructures as well. As the number of components in an electronic device doubles every 2 years (Moore’s law), transistors have shrunk that no longer can fit on conventional semiconductors such as silicon chips. But the 2D vdW heterostructures can allow this shrinking because of controlled electronic bandstructures and ultralow thickness.

1.2 2D materials discovery and classifications

First 2D material graphene was discovered [8] in 2004 by two researchers at the University of Manchester, Prof. Andre Geim and Prof. Kos...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• List of contributors
• Preface
• 1. Discovery and characterization of 2D materials and their heterostructures
• 2. Design and synthesis of two-dimensional materials and their heterostructures
• 3. Characterizations of nanoscale two-dimensional materials and heterostructures
• 4. Nanoheterostructured materials based on conjugated polymer and two-dimensional materials: synthesis and applications
• 5. Transition metal dichalcogenides based two-dimensional heterostructures for optoelectronic applications
• 6. Electronic and optoelectronic properties of the heterostructure devices composed of two-dimensional layered materials
• 7. Device physics and device integration of two-dimensional heterostructures
• 8. Electrocatalytic properties of two-dimensional transition metal dichalcogenides and their hetrostructures in energy applications
• 9. Emerging bio-applications of two-dimensional nanoheterostructure materials
• Index