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Title: Optical and magnetic resonance studies of point defects in single crystal diamond
Author: Green, Ben L.
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2013
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This thesis reports research on point defects in single crystal diamond studied by a number of techniques including electron paramagnetic resonance (EPR), ultraviolet-visible absorption (UV-Vis), photoluminescence (PL) and infrared absorption (IR). Natural diamond samples have been investigated, in addition to high pressure high temperature (HPHT) and chemical vapour deposition (CVD) grown synthetic diamond samples. The effects of low temperature electron irradiation on boron-doped synthetic diamond have been studied. For samples irradiated with 5 x 10 [superscript] 17 e-cm-2 at 100 K, the post-irradiation neutral boron and neutral vacancy concentrations are found to depend approximately linearly on the starting boron concentration in each sample. A CVD-grown sample is annealed and characterised at each annealing stage by PL, IR and UV-Vis. The results are explained in a model whereby some interstitials are mobile during irradiation and complex with the boron: there is no evidence for the interaction of boron and vacancies. The 1:913 eV (648:2 nm) photoluminescence transition is studied in type IIb diamond samples under applied uniaxial stress. The transition is found to occur between states of A' & A" symmetry. An associated local mode with energy 178:2meV (1437 cm-1) is determined to have A' symmetry. The emission is tentatively ascribed to a boron-containing interstitial complex. Complications of performing uniaxial stress on natural samples are discussed with reference to the 2:526 eV (490:8 nm) emission observed in plastically deformed type IIa diamond. Using 15N-doped HPHT-grown diamond, a new EPR spectrum is observed and identified as belonging to (NVN-). Hyperfine analysis shows that the unpaired electron probability density is localised approximately 100% on the two nearest neighbour carbon atoms. Using estimates of the 14N quadrupolar interaction strength, (NVN-) is identified in a 14N-doped synthetic diamond. The P2 spectrum is created in a 15N-doped synthetic sample following irradiation and HPHT annealing. The published spin Hamiltonian parameters are signifi cantly improved upon and for the first time the P2 spectrum is unambiguously assigned to (N3V)0. Both ([superscript]15 N 3 V)0 and ([superscript]15Ns)0 are shown to spin polarise upon illumination with light of energy A 2:4eV, with ([superscript]15 N s)0 spin polarisation argued to arise due to long-range interaction with ([superscript]15 N 3 V)0.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics