Table of Contents

 

††††††††††††††††† Title

††††††††††††††††† Abstract

††††††††††††††††† Acknowledgements

††††††††††††††††† Authorís Declaration

††††††††††††††††† List of Figures

††††††††††††††††† List of Tables
††††††††††††††††† Units and Nomenclature

 

†††† 1††††††††††† Introduction

††††††††† 1.0†††††††† Outline

†††††††† 1.1†††††††† The History of Diamond

†††††††† 1.2†††††††† Allotropes of Carbon

†††††††† 1.3†††††††† Properties of Diamond

†††††††† 1.4†††††††† The Synthesis of Diamond

†††††††† 1.5†††††††† Uses of Diamond

†††††††††††† 1.5.1††††† Abrasives

†††††††††††† 1.5.2††††† Thermal Management

†††††††††††† 1.5.3††††† Electronic Devices

†††††††††††† 1.5.4††††† Optical Windows

†††††††† 1.6†††††††† The Electrochemistry of Boron Doped Diamond

†††††††† 1.7†††††††† Summary

†††††††† 1.8†††††††† Outline of the Thesis

 

††† 2††††††††††† Growth and Characterisation of the Diamond Films

††††††††† 2.0†††††††† Outline

†††††††† 2.1†††††††† The Choice of Growth Technique

†††††††† 2.2†††††††† The Reaction Gases

†††††††† 2.3†††††††† The Mass Flow Controllers

†††††††† 2.4†††††††† Dilution of the Diborane Gas

†††††††† 2.5†††††††† The Deposition Chamber

†††††††† 2.6†††††††† The Substrate Heater

†††††††† 2.7†††††††† The Filaments

†††††††† 2.8†††††††† The Substrates

†††††††† 2.9†††††††† Electrical Contacts to the films

†††††††††††† 2.9.1††††† Indium/Gallium Eutectic

†††††††††††† 2.9.2††††† Silver Loaded Epoxy Resin

†††††††††††† 2.9.3††††† Three Layer Metalisation

†††††††††††† 2.9.4††††† Titanium Contacts

†††††††††††† 2.9.5††††† Summary

†††††††† 2.10†††††† Typical Growth Conditions

†††††††† 2.11†††††† Secondary Ion Mass Spectroscopy

†††††††† 2.12†††††† Scanning Electron Microscopy
and Optical Microscopy

†††††††† 2.13†††††† Laser Raman Spectroscopy

2.14               Summary

 

††††††††† 3††††††††††† Electrical Contacts

†††††††† 3.0†††††††† Outline

†††††††† 3.1†††††††† Introduction

†††††††† 3.2†††††††† Fabrication of Three Layer Metal Contacts

†††††††† 3.3†††††††† Fabrication of Titanium Underlayer Contacts

†††††††† 3.4†††††††† Characteristics of Silver Epoxy Resin Contacts

†††††††† 3.5†††††††† Characteristics of Evaporated Gold Contacts

†††††††† 3.6†††††††† Characteristics of Three Layer Metal Contacts

†††††††† 3.7†††††††† Characteristics of Titanium Underlayer Contacts

†††††††† 3.8†††††††† Four Point Probe Measurements

†††††††† 3.9†††††††† Summary

 

†††† 4††††††††††† Standard Electrochemical Theory

†††††††† 4.0†††††††† Outline

††††††††† 4.1†††††††† Metal Electrochemistry

††††††††† 4.2†††††††† Normal p-type Semiconductor Electrochemistry

††††††††† 4.3†††††††† Highly Doped Semiconductors

††††††††† 4.4†††††††† Surface State Mediated Electrode Transfer

††††††††††††† 4.4.1††††† Contributions to the Applied Potential

††††††††††††† 4.4.2††††† Contributions of the Helmholtz Layer
and the Space Charge Region

††††††††††††† 4.4.3††††† Electrical Charge at the Surface
of a Semiconductor Electrode

††††††††††††† 4.4.4††††† The Butler-Volmer Equation

††††††††††††† 4.4.5††††† Schottky Diode

††††††††††††† 4.4.6††††† Model

††††††††† 4.5†††††††† Steady State Current

††††††††† 4.6†††††††† Summary

 

†††† 5††††††††††† The Electrochemistry of Highly Doped Diamond Films

†††††††† 5.0†††††††† Outline

††††††††† 5.1†††††††† Experimental Set-up

††††††††††††† 5.1.1††††† Electrolyte Solutions

††††††††††††† 5.1.2††††† Electrochemical Cells

††††††††††††† 5.1.3††††† Reference Electrodes

††††††††††††† 5.1.4††††† Counter Electrodes

††††††††††††† 5.1.5††††† Potentiostats

††††††††††††† 5.1.6††††† Faraday Cages

††††††††† 5.2†††††††† The Cyclic Voltammetry Technique

††††††††††††† 5.2.1††††† Reversible Electrode Dynamics

††††††††††††† 5.2.2††††† Irreversible Electrode Dynamics

††††††††††††† 5.2.3††††† Quasi-Reversible Electrode Dynamics

††††††††† 5.3†††††††† Cyclic Voltammetry in Dilute Nitric Acid

††††††††† 5.4†††††††† Cyclic Voltammetry of 4-Aminophenol

††††††††† 5.5†††††††† Cyclic Voltammetry of Potassium Ferrocyanide

††††††††† 5.6†††††††† Cyclic Voltammetry of Ferrous Sulphate and Ferric Sulphate

††††††††† 5.7†††††††† Mott-Schottky Plots

††††††††† 5.8†††††††† AC Impedance

††††††††† 5.8†††††††† Moderately Doped Films

5.9                   Summary

 

†††† 6††††††††††† The Electrochemistry of Low Doped Diamond Films

††††††††† 6.0†††††††† Outline

††††††††† 6.1†††††††† Experimental Set-up

†††††††† 6.2†††††††† Surface Termination

†††††††† 6.3†††††††† Cyclic Voltammetry of oxygen-terminated low-doped diamond

6.3.1††††† Cyclic Voltammetry of Ferrous Sulphate and Ferric Sulphate

6.3.2††††† Cyclic Voltammetry of Potassium Ferrocyanide and Potassium Ferricyanide

††††††††† 6.3.3††††† Cyclic Voltammetry of Other Redox Couples

6.4†††††††† Cyclic Voltammetry of hydrogen-terminated low-doped diamond

6.5†††††††† Cyclic Voltammetry of low-doped diamond with indeterminate surface termination

6.5.1            Cyclic Voltammetry of Ferrous Sulphate and Ferric Sulphate

6.5.2            Cyclic Voltammetry of Potassium Ferrocyanide and Potassium Ferricyanide in an Aqueous Solution of Potassium Chloride

6.5.3††††† Cyclic Voltammetry of Potassium Ferrocyanide and Potassium Ferricyanide in an Aqueous Solution of Potassium Hydroxide

6.6†††††††† Concentration Effects

6.7†††††††† Mott-Schottky Plots

6.8†††††††† Summary

 

†††† 7††††††††††† Theoretical Model for the Electrochemistry of Boron Doped Diamond

†††††††† 7.0†††††††† Outline

†††††††† 7.1†††††††† Interpreting the Metallic Behaviour of Highly Doped Diamond

†††††††† 7.2†††††††† Explanation of the Metallic Behaviour of Highly Doped Diamond

7.2.1††††† Hydrogen Terminated Diamond

7.2.2††††† Oxygen Terminated Diamond

††††††††† 7.3†††††††† The relationship between current density and applied potential

7.3.1††††† Special cases of the current density - applied potential relationship

††††† 7.3.1.1††††† The case where |j0H| >> |j|

††††† 7.3.1.2††††† The case where |j| >> |j0H|

††††† 7.3.1.3††††† The case where |j0SC| >> |j| and j Ľ j0H

7.3.2††††† The current density - applied potential relationship at intermediate values

††††††††† 7.4†††††††† AC Impedance and the Surface State Model

††††††††† 7.5†††††††† Interpreting the Semiconductor Behaviour of Low Doped Diamond

††††††††† 7.6†††††††† Summary

†††† 8††††††††††† Intensity Modulated Photocurrent Spectroscopy

†††††††† 8.0†††††††† Outline

†††††††† 8.1†††††††† Intensity Modulated Photocurrent Spectroscopy (IMPS)

†††††††† 8.2†††††††† Experimental Set-up

†††††††† 8.3†††††††† Experimental Results

†††††††† 8.4†††††††† Theory

8.4.1††††† Effect of Constant Illumination on the Current Density

8.4.2        Effect of Modulated Illumination on the Current Density

††††††††† 8.5†††††††† Summary

 

†††† 9††††††††††† Conclusions

†††††††† 9.1†††††††† Background

†††††††† 9.2†††††††† Growth and Characterisation

†††††††† 9.3†††††††† Electrical Contacts

†††††††† 9.4†††††††† Standard Electrochemical Theory

†††††††† 9.5†††††††† Electrochemistry of Highly and Moderately Doped Diamond Films

†††††††† 9.6†††††††† Electrochemistry of Low Doped Diamond Films

†††††††† 9.7†††††††† Electrochemical Theory for Boron Doped Diamond Films

†††††††† 9.8†††††††† Intensity Modulated Photocurrent Spectroscopy

††††††††† 9.9†††††††† Possible Future Work

 

†††† A††††††††††† Appendix A: Levels of Impurities

†††††††† A.1†††††††† potassium chloride, KCl

†††††††† A.2†††††††† potassium hydroxide, KOH

†††††††† A.3†††††††† sodium chloride, NaCl

†††††††† A.4†††††††† ferrous sulphate heptahydrate, FeSO4.7H2O

†††††††† A.5†††††††† ferric sulphate pentahydrate, Fe(SO4)3.5H2O

†††††††† A.6†††††††† ferric nitrate nonahydrate, Fe(NO3)3.9H2O

 

†††† B††††††††††† Appendix B: Summary of Diamond Growth Runs

 

†††† C††††††††††† Appendix C: References