Defects in Two-Dimensional Materials

Front Cover
Defects in Two-Dimensional Materials
Copyright
Contents
List of contributors
About the editors
Preface
1 Introduction
	References
2 Physics and theory of defects in 2D materials: the role of reduced dimensionality
	2.1 Introduction
	2.2 Classification of defects
	2.3 Insights into the atomic structures of defects from scanning tunneling and transmission electron microscopy experiments
	2.4 Production of defects in two-dimensional materials under electron and ion irradiation
	2.5 Examples of defects in two-dimensional materials
		2.5.1 Point defects
		2.5.2 Line defects
	2.6 Theoretical aspects of the physics of defects in bulk crystalline solids and two-dimensional materials
		2.6.1 Defect formation energy
		2.6.2 Gibbs free energy of defect formation
		2.6.3 Equilibrium concentration of defects
	2.7 Calculations of defect formation energies and electronic structure using the supercell approach
		2.7.1 Assessment of defect formation energies
		2.7.2 First-principles approaches for calculating defect states
	2.8 Electronic structure of 2D materials with defects
		2.8.1 Defect-induced modifications of electronic states
		2.8.2 Deep vs. shallow electronic states in 2D materials
		2.8.3 Defect-bound excitons
	2.9 Point defects and vibrational properties of 2D materials from atomistic simulations
		2.9.1 Signatures of defects in Raman spectra
		2.9.2 Phonon contributions to defect-related photo-luminescence spectra in 2D materials
	2.10 Conclusions and outlook
	Acknowledgment
	References
3 Defects in two-dimensional elemental materials beyond graphene
	3.1 Introduction
	3.2 Borophene
		3.2.1 Synthesis and atomic structure
		3.2.2 Defects in borophene
	3.3 Silicene
		3.3.1 Synthesis and atomic structure
		3.3.2 Defects in silicene
	3.4 Germanene
		3.4.1 Synthesis and atomic structure
		3.4.2 Defects in germanene
	3.5 Stanene
		3.5.1 Synthesis and atomic structure
		3.5.2 Defects in stanene
	3.6 Plumbene
		3.6.1 Synthesis and atomic structure
		3.6.2 Defects in plumbene
	3.7 Phosphorene
		3.7.1 Synthesis and atomic structure
		3.7.2 Defects in phosphorene
	3.8 Arsenene (h-As) and Antimonene (h-Sb)
		3.8.1 Synthesis and atomic structure
		3.8.2 Defects in arsenene and antimonene
	3.9 Bismuthene
		3.9.1 Synthesis and atomic structure
		3.9.2 Defects in bismuthene
	3.10 Selenene and tellurene
	3.11 Gallenene
	3.12 Hafnene
	3.13 Conclusions and outlook
	References
4 Defects in transition metal dichalcogenides
	4.1 Introduction
	4.2 Point defects
		4.2.1 Defect inventory
		4.2.2 Defect classification
		4.2.3 The nature of vacancies
		4.2.4 Complex defects created by annealing of WSe2
	4.3 Impurities
		4.3.1 Contaminants
		4.3.2 Intercalants
		4.3.3 Dopants
		4.3.4 Alloys
	4.4 Line defects
	4.5 Control of defects and their applications
	4.6 Summary
	References
5 Realization of electronic grade graphene and h-BN
	5.1 Challenges overview: growth, transfer, and integration
	5.2 Apparatus and methodology overview
		5.2.1 Bulk crystal production and layer exfoliation
		5.2.2 Chemical vapor deposition and related methods overview
	5.3 Scalable growth by chemical vapor deposition
		5.3.1 Pyrolytic growth
		5.3.2 Catalytic CVD: substrate and catalyst effects
		5.3.3 Catalytic CVD: growth parameters and process optimization
			5.3.3.1 Overview
			5.3.3.2 Precursor choice
			5.3.3.3 Process pressure
			5.3.3.4 Precursor and auxiliary gas pressures
			5.3.3.5 Temperature
			5.3.3.6 Time-dependent controls
	5.4 Material optimization
		5.4.1 Designed catalysts
			5.4.1.1 Oxidation & impurity scavenging
			5.4.1.2 Catalyst bulk solubility tuning
			5.4.1.3 Designed solubility by alloying
			5.4.1.4 Growth on liquid surfaces
			5.4.1.5 Solid source precursors
		5.4.2 Transfer routes overview
		5.4.3 State-of-the-art: large area single 2D crystal production
			5.4.3.1 Single domain growth
			5.4.3.2 Domain stitching
			5.4.3.3 Large area production
	5.5 Conclusions and outlook
	References
6 Realization of electronic-grade two-dimensional transition metal dichalcogenides by thin-film deposition techniques
	6.1 Current challenges in transition metal dichalcogenide synthesis
	6.2 Current synthesis techniques
		6.2.1 Reactor design
		6.2.2 Solid-source chemical vapor deposition (SS-CVD)
		6.2.3 Metal-organic chemical vapor deposition (MOCVD)
		6.2.4 Molecular beam epitaxy (MBE)
	6.3 Controlling nucleation and crystal growth
		6.3.1 Substrate engineering
		6.3.2 Precursor chemistry
		6.3.3 Impact of growth temperature
		6.3.4 Impact of growth pressure
	6.4 Materials engineering
		6.4.1 Defect engineering
		6.4.2 Heterostructures
		6.4.3 Doping and alloying
	6.5 Summary
		Note
	Acknowledgments
	References
7 Materials engineering – defect healing & passivation
	7.1 Introduction
	7.2 Defect formation and healing in 2D TMDs
		7.2.1 Point defects
		7.2.2 Line defects
	7.3 Defect engineering by chemical treatment and applications
		7.3.1 Vacancy healing
		7.3.2 Covalent functionalization
		7.3.3 Interfacial charge transfer
	7.4 Defect control by external sources
		7.4.1 Thermal annealing
		7.4.2 Electron beam irradiation
		7.4.3 Plasma treatment
		7.4.4 Encapsulation
	7.5 Future perspectives
	References
8 Nonequilibrium synthesis and processing approaches to tailor heterogeneity in 2D materials
	8.1 Introduction
	8.2 Non-equilibrium synthesis – effects of chemical potential on the heterogeneity of 2D materials
		8.2.1 Point defects control by nonequilibrium laser-based synthesis and Au-assisted CVD growth
		8.2.2 Forming line defects, edges, and morphologies of 2D materials through controlled kinetics
	8.3 Strain induced phenomena in 2D materials
		8.3.1 Strain estimates from PL/absorption spectra
		8.3.2 Strain estimates from Raman spectra
		8.3.3 Second harmonic generation (SHG) for strain estimates
		8.3.4 Extended compressive strain at grain boundaries of merged monolayer crystals
		8.3.5 Strain generation by growth on curved surfaces: strain tolerant growth
		8.3.6 Strain induced 2D crystal growth acceleration
		8.3.7 Strain induced exciton funneling: single photon emitters
	8.4 Heterogeneity introduced by the self-assembly of nanoscale `building blocks\'
	8.5 The effects of kinetic energy on defects and doping: hyperthermal implantation for the formation of Janus monolayers
	8.6 Summary and outlook
	Acknowledgments
	References
9 Two-dimensional materials under ion irradiation: from defect production to structure and property engineering
	9.1 Introduction
	9.2 Response of two-dimensional materials to ion irradiation: theoretical aspects
		9.2.1 Theoretical background and methods
		9.2.2 Simulations of ion impacts on free-standing 2D materials
		9.2.3 Simulations of ion irradiation of supported 2D materials
		9.2.4 Simulations of the interaction of light or swift ions with two-dimensional materials when electronic stopping dominates
	9.3 Experiments on ion irradiation of two-dimensional materials
		9.3.1 Low- and medium-energy heavy ion irradiation of two-dimensional materials and direct ion implantation
		9.3.2 High-energy proton irradiation
		9.3.3 Swift heavy ions
		9.3.4 Highly charged ions
		9.3.5 Atomic structure engineering by using focused ion beams
		9.3.6 Irradiation tolerance
	9.4 Applications
	9.5 Summary, challenges, and outlook
	Acknowledgments
	References
10 Tailoring defects in 2D materials for electrocatalysis
	10.1 Introduction
	10.2 Defect-tailored 2D electrocatalysts for hydrogen evolution reaction (HER)
		10.2.1 Fundamental principles of electrocatalytic HER
		10.2.2 Catalytic activity descriptors of electrocatalytic HER
		10.2.3 Defect-tailored 2D electrocatalysts for HER
	10.3 Defect-tailored 2D electrocatalysts for oxygen evolution reaction (OER)
		10.3.1 Fundamental principles of electrocatalytic OER
		10.3.2 Catalytic activity descriptors of electrocatalytic OER
		10.3.3 Defect-tailored 2D electrocatalysts for OER
	10.4 Defect-tailored 2D electrocatalysts for nitrogen reduction reaction (NRR)
		10.4.1 Fundamental principles of electrocatalytic NRR
		10.4.2 Catalytic activity descriptors of electrocatalytic NRR
		10.4.3 Defect-tailored 2D electrocatalysts for NRR
	10.5 Defect-tailored 2D electrocatalysts for carbon dioxide reduction reaction (CO2RR)
		10.5.1 Fundamental principles of electrocatalytic CO2RR
		10.5.2 Catalytic activity descriptors of electrocatalytic CO2RR
		10.5.3 Defect-tailored 2D electrocatalysts for CO2RR
	10.6 Challenges and perspectives of defect engineering for 2D electrocatalysts
	Acknowledgments
	References
11 Devices and defects in two-dimensional materials: outlook and perspectives
	11.1 Introduction
	11.2 Defect characterization in 2D TMDs using ultrafast pump-probe spectroscopy
		11.2.1 Motivation
		11.2.2 Pump-probe spectroscopy
		11.2.3 Point defects
		11.2.4 Edges/grain boundaries
	11.3 Devices fabricated on 2D CVD-grown TMDs
		11.3.1 Effect of top gate dielectrics
			11.3.1.1 Al2O3
			11.3.1.2 HfO2
			11.3.1.3 ZrO2
		11.3.2 Embedded gate FETs
		11.3.3 Effect of growth substrates
			11.3.3.1 Al2O3
			11.3.3.2 ZrO2
		11.3.4 Effect of encapsulation and protective layer
		11.3.5 Defects in CVD MoS2
		11.3.6 MOCVD MoS2
	11.4 Devices fabricated on MBE-grown TMDs
	11.5 2D van der Waals (vdW) heterostructures
		11.5.1 Device fabrication
		11.5.2 Applications
	11.6 Enhancing 2D device performance using defect engineering
		11.6.1 Defect passivation techniques
		11.6.2 Doping & defect engineering using dielectrics
		11.6.3 Substitutional doping & alloying
	11.7 Theoretical investigation of defects in 2D TMDs
		11.7.1 Computational details
		11.7.2 Results and discussion
			11.7.2.1 Monolayer MoS2 on HfO2 slab
			11.7.2.2 Monolayer MoS2 on HfO2 slab with O vacancy
			11.7.2.3 Mo and S vacancies in MoS2
	References
12 Concluding remarks
	References
Index
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