In the past decade the interest in molecular electronic devices has escalated. The synthesis of molecular crystals has improved, providing single crystals or thin films with mobility comparable with or even higher than amorphous silicon. Their mechanical flexibility admits new types of applications and usage of electronic devices. Some of these organic crystals also display magnetic effects. Furthermore, the fullerene and carbon nanotube allotropes of carbon are prominent candidates for various types of applications. The carbon nanotubes, in particular, are suitable for molecular wire applications with their robust, hollow and almost one-dimensional structure and diverse band structure. In this thesis, we have theoretically investigated carbon based materials, such as carbon nanotubes, pentacene and spiro-biphenalenyl neutral radical molecular crystals. The work mainly deals with the electron structure and the transport properties thereof. The first studies concerns effects and defects in devices of finite carbon nanotubes….
Contents
1 Introduction
1.1 Background and motivation
1.2 Materials
1.2.1 Organic carbon
1.2.2 Pristine carbon
1.3 Methods
2 Electronic structure
2.1 Relaxation of the nuclear configuration
2.2 Electronic structure methods
2.2.1 Non-interacting electrons
2.2.2 The Hartree-Fock method
2.2.3 Density-functional theory
2.2.4 The Thomas-Fermi-Dirac approximation
2.2.5 The Hohenberg-Kohn theorems
2.2.6 The Kohn-Sham ansatz
2.2.7 Exchange-correlation functionals
2.2.8 Spin-density functionals
2.2.9 The Vienna ab-initio simulation package
2.2.10 The tight-binding and the H¨uckel approximation
3 Electronic transport
3.1 The band theory of periodic solids
3.2 The semi-classical model of electron transport
3.3 The Landauer formalism
4 Materials
4.1 Carbon nanotubes
4.1.1 Growth methods
4.1.2 Properties
4.2 Pentacene
4.3 Phenalenyl-based neutral radical
5 Summary of the papers
5.1 Paper I
5.2 Paper II
5.3 Paper III
5.4 Paper IV
5.5 Paper V
Bibliography
List of Publications
Paper I
Paper II
Paper III
Paper IV
Paper V
Author: Hansson, Anders
Source: Linköping University
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