Carbon forms a variety of allotropes due to the diverse hybridization of s- and p-electron orbitals, including the time-honored graphite and diamond as well as new forms such as C60 fullerene, nanotubes, graphene, and carbyne. The new family of carbon isotopes—fullerene, nanotubes, graphene, and carbyne—is called “nanostructured carbon” or “nanocarbon.” These isotopes exhibit extreme properties such as ultrahigh mechanical strength, ultrahigh charge–carrier mobility, and high thermal conductivity, attracting considerable attention for their electronic and mechanical applications as well as for exploring new physics and chemistry in the field of basic materials science. Electron sources are important in a wide range of areas, from basic physics and scientific instruments to medical and industrial applications. Carbon nanotubes (CNTs) and graphene behave as excellent electron-field emitters owing to their exceptional properties and offer several benefits compared to traditional cathodes. Field emission (FE) produces very intense electron currents from a small surface area with a narrow energy spread, providing a highly coherent electron beam—a combination that not only provides us with the brightest electron sources but also explores a new field of electron beam–related research.
This book presents the enthusiastic research and development of CNT-based FE devices and focuses on the fundamental aspects of FE from nanocarbon materials, including CNTs and graphene, and the latest research findings related to it. It discusses applications of FE to X-ray and UV generation and reviews electron sources in vacuum electronic devices and space thrusters. Finally, it reports on the new forms of carbon produced via FE from CNT.
Author(s): Yahachi Saito
Publisher: Jenny Stanford Publishing
Year: 2022
Language: English
Pages: 373
City: Singapore
Cover
Half Title
Title Page
Copyright Page
Table of Contents
Preface
Chapter 1: FEM and FIM of Carbon Nanotubes
1.1: Structure of CNT and Electron Emission Properties
1.2: FEM of CNT
1.2.1: MWCNT with a Closed Cap
1.2.2: Thin MWCNT with a Cone-Shaped Tip
1.2.3: SWCNTs
1.2.4: MWCNT with an Open Tip
1.3: Energy Spectra of Emitted Electrons
1.4: Field-Emission Study of CNT in TEM
1.5: FIM of CNT
1.5.1: Capped MWCNT
1.5.2: Broken Tip and Open-Ended MWCNT
1.5.3: SWCNT and DWCNT Bundles
1.6: Summary and Conclusion
Chapter 2: Electromechanical Self‐Oscillations of Carbon Field Emitters
2.1: Introduction
2.2: Introduction to Electromechanical Self-Oscillators
2.2.1: Self-Oscillation
2.2.2: General Model of Self-Oscillations: The Van der Pol Oscillator
2.2.3: Specificity of the Single Clamped Field-Emission Geometry
2.3: Self-Oscillations of Individual Carbon Nano-emitters
2.3.1: First Observations
2.3.1.1: The “head-shaking” effect
2.3.1.2: Self-oscillations on SWCNT
2.3.2: Characterization of Nano-electromechanical Self-Oscillating Field Emitters
2.3.2.1: Self-sustained oscillations in an electronic microscope
2.3.2.2: Self-oscillations in an ultrahigh vacuum environment
2.3.3: Toward Large Scale Integration
2.4: Self-Oscillation for Large Carbon Emitters
2.4.1: Self-Oscillations from Assembly of Nanotubes
2.4.2: Very High Current with Carbon Fiber Self-Oscillators
2.5: Conclusion
Chapter 3: Performance of Point-Typed Carbon Nanotube Field Emitters
3.1: Introduction
3.2: Point-Typed CNT Field Emitter Made of a CNT Bundle
3.3: Point-Typed CNT Field Emitter Made of a CNT Yarn
3.4: Point-Typed CNT Field Emitter Made of a CNT Film
3.5: Point-Typed CNT Field Emitter Fabricated by CNT Paste
3.6: Point-Typed CNT Field Emitter Made of a Free-standing CNT Film
3.7: Summary
Chapter 4: Theoretical Field-Emission Patterns from Carbon Nanotubes
4.1: Introduction
4.2: Field-Emission Patterns from CNTs Calculated Using TD-DFT
4.2.1: TD-DFT
4.2.2: Method and Computational Details
4.2.3: Results and Discussion
4.3: Field-Emission Patterns from CNT Calculated Using DFT
4.3.1: Theoretical Models for Calculating Field-Emission Patterns
4.3.2: Method and Computing Details
4.3.3: Results and Discussions
4.4: Conclusion
Chapter 5: Heat Localization and Thermionic Emission from Carbon Nanotubes
5.1: Introduction
5.2: Thermionic Emission from Carbon Nanotubes
5.3: Heat Localization in Carbon Nanotube Forests Leading to Thermionic Emission
5.3.1: The Heat Trap Effect
5.3.2: The Effect of Photon Wavelength and Combined Multiphoton Thermal Photoemission
5.3.3: The Effect of Polarization and Temporal Behavior
5.3.4: The Mechanism of Heat Localization
5.3.5: Applications of Thermionic Emission Due to Heat Trap
5.4: Conclusion and Outlook: The Future of Thermionic Emission from Carbon Nanotubes
5.5: Acknowledgments
Chapter 6: Field Emission from the Edges of Single-Layer Graphene
6.1: Introduction
6.2: Survey of Theoretical Work
6.3: Survey of Experimental Work
6.4: UHV Studies of Free-Standing, Individual, Cleaned, Graphene Flakes
6.5: Summary and Perspectives
Chapter 7: FEM and FIM of Graphene
7.1: Introduction
7.2: FEM of Graphene
7.2.1: Preparation of Graphene Emitter
7.2.2: “Lip” Pattern Typical of Graphene Field Emitter
7.2.3: Change of FEM Images from “Lip” to Dim Pattern
7.2.4: Origin of “Lip” Pattern
7.2.5: Frequent Encounter of “Lip” Patterns in Graphene-Related Materials
7.3: FIM of Graphene
7.3.1: FIM Images of Graphene
7.3.2: Historic Survey of Graphite FIM
7.4: Conclusion
Chapter 8: Spin-Polarized Field-Emitted Electrons from Graphene Oxide Edges
8.1: Introduction
8.2: Experimental Method
8.3: Spin Polarization at Edges of Graphene Oxide
8.4: Change in Spin Polarization Due to Adsorption
8.5: Conclusion and Remarks
Chapter 9: Theoretical Coherent Field Emission of Graphene
9.1: Coherent Cold Field Emission
9.2: Graphene Emitter with a Uniform Edge
9.3: Path-Decomposition Approach
9.4: CFE Patterns of Graphene
9.4.1: Quantum States
9.4.2: Emission Waves and Patterns
9.5: Discussions and Summary
Chapter 10: Influence of Edge Structures of Graphene on Field-Emission Properties
10.1: Introduction
10.2: Theoretical Procedures
10.3: Structural Models
10.4: Edge-Shape Effect on the Field-Emission Property of Graphene
10.5: Edge-Functionalization Effect on the Field-Emission Property of Graphene
10.6: Conclusion
Chapter 11: Theory of Thermionic Electron Emission for 2D Materials
11.1: Introduction
11.2: Thermionic Emission
11.3: Field Emission
11.4: Thermionic Emission Models for 2D Materials
11.4.1: Motivation
11.4.2: General Formalism of Electron Emission in 2D Materials
11.4.3: Dirac Cone Model of Graphene
11.4.4: Graphene Vertical Thermionic Emission: k||-Conserving Model
11.4.5: Graphene Vertical Thermionic Emission: k||-Nonconserving Model
11.4.6: Graphene Vertical Thermionic Emission at High-Energy Regime
11.4.7: Universal Thermionic Emission Model
11.5: Conclusion and Outlooks
Chapter 12: Direct Grown Vertically Full Aligned Carbon Nanotube Electron Emitters for X-Ray and UV Devices
12.1: Introduction
12.2: Synthesis of Vertically Aligned Carbon Nanotube Arrays
12.3: Carbon Nanotube as a Cold Cathode
12.3.1: Diode-Based FE Device Structure with CNT Cold Cathodes
12.3.2: Triode-Based FE Device Structure with CNT Cold Cathodes
12.3.2.1: The effect of alignment of CNT emitter to gate electrode
12.3.2.2: The effect of thermal stability of gate electrode
12.4: X-Ray Imaging with C-Beam
12.5: UV Irradiative Applications with C-Beam
12.6: Summary
Chapter 13: Development of CNT X-Ray Technology for Medical and Dental Imaging
13.1: Introduction
13.1.1: Conventional Thermionic X-Ray
13.1.2: Field-Emission X-Ray
13.1.3: CNT Field-Emission X-Ray
13.2: CNT X-Ray Devices
13.2.1: CNT Cathode
13.2.2: Single-Beam CNT X-Ray Source
13.2.3: Spatially Distributed CNT X-Ray Source Array
13.3: Medical and Dental Imaging Applications
13.3.1: Motivation
13.3.2: CNT X-Ray-Based Stationary Digital Tomosynthesis
13.3.2.1: Detection of breast cancer
13.3.2.2: Chest imaging
13.3.2.3: Dental imaging
13.4: Conclusions
Chapter 14: Graphene Cold Field-Emission Sources for Electron Microscopy Applications
14.1: Introduction
14.2: Work Function
14.3: Energy Distribution
14.3.1: Theoretical Background
14.3.2: Statistical Coulomb Interactions
14.3.3: Measured Values of the FWHM Energy Spread for the Graphene Cold Field Electron
14.4: Source Electron Optics
14.5: Current Fluctuations
14.5.1: Short-Term Current Fluctuations
14.5.2: Long-Term Current Drift
14.6: Summary
Chapter 15: CNT Field-Emission Cathode for Space Applications
15.1: Introduction
15.2: Overview of KITE
15.3: CNT Cathode for KITE
15.3.1: CNT Cathode Module
15.3.2: Structure and Characteristics of CNT Cathode
15.3.3: Electrical Circuit and Operation of CNT Cathode
15.3.4: Unique Treatment for Use in Space
15.3.4.1: Consideration of atomic oxygen in low Earth orbit
15.3.4.2: Tolerance to mechanical and thermal environments
15.4: Results and Findings of On-Orbit Operation of CNT Cathodes
15.4.1: Overview of Cathode Operation
15.4.2: I–V Characteristics and Tolerance to Atomic Oxygen Environment On-Orbit
15.4.3: Electron Emission Behavior to Ambient Space Plasma
15.5: Next Steps
15.6: Conclusion
Chapter 16: Growth of Long Linear Carbon Chains after Serious Field Emission from a CNT Film
16.1: Introduction
16.2: Field Electron Emission Accompanied with Electrical Discharge for Single-Wall Carbon Nanotube Films
16.3: Long Linear Carbon Chains in Single-Wall Carbon Nanotube Films after Electrical Discharge
16.4: Conclusions
Chapter 17: Emission of C20+ by Field Evaporation from CNT
17.1: Introduction
17.2: Field Evaporation of Carbon Ions from CNT Under High Electric Field
17.3: Magic Cluster Ion, C20+, in Field Evaporation Mass Spectra
17.4: Other Evidences of the Existence of C20 Clusters in Gas Phase
17.5: Conclusion
Index
