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Identification and characterisation of point defects in CVD diamond
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Nako, Enrik (2020) Identification and characterisation of point defects in CVD diamond. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3736122
Abstract
This thesis reports research on the identification and characterisation of point defects in chemical vapour deposition (CVD) grown synthetic diamond. Investigation has been facilitated by a number of techniques, including electron paramagnetic resonance (EPR), infrared (IR) and ultraviolet-visible (UV-Vis) absorption, and photoluminescence (PL) spectroscopies. The perturbing effect of uniaxial stress on the symmetry of defects has also been utilised in conjunction with IR absorption and PL spectroscopies.
The electronic structure of the neutral silicon vacancy centre (SiV0), and in particular the 946nm zero-phonon line (ZPL) transition, is investigated. Through PL measurements with uniaxial stress, the 946nm ZPL is assigned to a 3Eu _ 3A2g transition where the 3Eu excited state is coupled to a 3A2u shelving state 6:8meV lower in energy. The symmetry-forbidden transition between the 3A2g ground state and 3A2u shelving state is observed (at approximately 951 nm) upon applied stress that lowers the D3d symmetry of SiV0, and a scheme is proposed for spin-dependent initialisation and readout of the spin states. A pseudo-local vibrational mode (pLVM) of the SiV0 centre is identified at 976 nm.
IR absorption and PL measurements of nitrogen-doped CVD diamond will often observe a hydrogen-related line at 7354 cm−1/1360 nm, and a suite of diamonds containing this feature are studied. The 7354 cm−1 centre is observed to exhibit preferential orientation relative to the growth direction when grown on {0 0 1}- and {1 1 0}-oriented substrates, which is subsequently lost upon annealing at a temperature of at least 1000 XC. Upon thermal treatment the 7354 cm−1 line will charge transfer and increase in intensity, given a sufficient concentration of acceptors are also present. The excited state of the 7354 cm−1 transition is determined to be degenerate through thermalisation experiments, whilst under applied stress, with a purpose-built PL spectrometer equipped with 1064nm excitation. Previous results allow for the 7354 cm−1 line to be assigned to (at least) an E ↔ E transition, but the exact symmetry of the defect responsible for the transition cannot be confidently determined.
An annealing study of two brown-coloured boron-doped CVD diamonds is also reported. Upon annealing between 1000{1500 XC, the brown-colouration is progressively annealed-out along with a number of unidentified features in the UVVis absorption spectra; simultaneously, IR absorption measurements observe a progressive increase in the uncompensated boron concentration. A large number of unreported features are also observed with IR absorption measurements, which show negligible change in intensity from annealing and charge transfer treatment. However, most are 100% preferentially orientated either parallel or perpendicular to the growth direction of the diamond. It is also the case with PL measurements that many unidentified ZPLs are observed. The nature of the majority of spectroscopic features observed in these boron-doped diamonds is currently unknown.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QC Physics T Technology > TP Chemical technology T Technology > TS Manufactures |
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Library of Congress Subject Headings (LCSH): | Diamonds, Artificial, Diamonds -- Defects, Diamonds, Artificial -- Defects, Point defects, Chemical vapor deposition, Electron paramagnetic resonance | ||||
Official Date: | January 2020 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Physics | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Newton, Mark E. | ||||
Sponsors: | De Beers LV (Firm) | ||||
Format of File: | |||||
Extent: | xvii, 198 leaves : illustrations | ||||
Language: | eng | ||||
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