An optoelectronic study of diamond grown by chemical vapour deposition

This thesis is concerned with the characterisation of CVD diamond via spectroscopic and electrical investigations. Much of the work concentrates on the identification and the effects of defects and impurities. The bulk of the experimental results are from photoconductivity studies of CVD diamond configured as a detector of ultraviolet light. Other investigations include the annealing of radiation damage in CVD diamond and an electrical characterisation of boron-doped CVD diamond. The characterisation of some group III nitrides forms the short appendix. The work is organised into chapters which are outlined below. Chapter 1 - Introduction: This gives some background to the properties of diamond, its uses, and the different synthesis techniques. Also given is a short review of some of the optical centres in natural and CVD diamond. The kinetics of migration, which is relevant to later chapters is also discussed. Chapter 2 - Experimental Details: This chapter details the experimental techniques and apparatus used in all investigations. An outline of the electronics and data acquisition technique is also presented. Chapter 3 - The Annealing of Radiation Damage: This gives the annealing behaviour of some absorption features in natural and CVD diamond which has been irradiated with electrons. A correlation has been made between the annealing behaviour of two optical centres, and the fast and slow components of a vacancy related centre are explained. Chapter 4 - Electrical characterisation of boron-doped CVD diamond: The boron-doped diamonds studied in this chapter were intended for use as a detector of neutrons. This required a concentration of boron which is large enough for the detection process to occur but low enough for the 'leakage' current to not dominate any induced signal. This electrical characterisation measures the resistivities ( and the temperature dependence ) of the samples and compares this to other work to estimate boron concentrations. Chapter 5 - CVD Diamond Configured as a Detector of Ultraviolet light: This chapter is concerned with quite an extensive study of the photoconductive behaviour of CVD diamond. There are three main sections of results which include spectroscopic studies, time response studies, and area dependence studies. Many of the results are compared to those from a commercially available silicon detector. An interpretation of observed photoconductive gain is presented. Appendix: The group III nitrides have become increasingly important materials due to their many potential applications. This short chapter is a characterisation of gallium and aluminium nitride using cathodoluminescence spectroscopy. The material was grown using a new technique and the results form a 'proof of principle' for this growth method. (author)Available from British Library Document Supply Centre-DSC:DXN034808 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo