A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy / Raman and photoluminescence (PL) spectroscopy techniques were used to investigate the mechanical properties of diamond and cubic boron nitride (cBN) by optical means. Both these materials have extreme mechanical properties that make them the material of choice for many industrial applications, ranging from cutting and grinding to wire-drawing dies. The results obtained on single crystal diamond, polycrystalline diamond (PCD) and cBN are summarised below. Micro-Raman and photoluminescence (PL) spectroscopy were used to map the threedimensional (3D) stress and deformation distributions surrounding a plastic impression made in a synthetic, type Ib single crystal diamond. Using data from the Raman peak position, a 3D map of the stress contours surrounding the impression was generated, while the Raman width data yielded a map of the plastic deformation volume. The stress contours compare favorably with the resolved shear stress contours calculated for diamond. PL intensity maps of the zero phonon line (ZPL) associated with the [N-V]– defect centre at 1.945eV provide images of the extent of vacancy formation and movement during the impression process. Data concerning the position and width of the ZPL correspond well with the Raman results. Polycrystalline diamond (PCD) tools commonly consist of a PCD layer sintered onto a cobalt-tungsten carbide (Co-WC) substrate. These tools are used in diverse applications and both the magnitude and distribution of the stresses in the PCD layer affect tool behavior. These stresses in sample drillbits were investigated by means of micro-Raman spectroscopy. Cyclic annealing of a sample drillbit to 600 oC shows that the tool properties are retained after 5 cycles, while similar cycling to 800 oC resulted in a permanent decrease of the average surface compressive stress. This implies a reduction in the drillbit’s ability to resist crack formation and propagation and is thus a degradation of the tool properties. The method of Raman mapping of stress and deformation in diamond was also applied to single crystals of cBN. Indentations on cubic boron nitride (cBN) crystals and polycrystalline cubic boron nitride (PcBN) composites were mapped and the shifts of the cBN Raman lines from their unstressed positions used to quantify the residual stresses in the boron nitride due to the deformation brought about by the indentation. These were found to be of the order of 1 GPa. vi These measurements illustrated for the first time the use of Raman spectroscopy to study residual stresses in boron nitride. Defects in cBN were studied using photoluminescence spectroscopy at low temperature (< 10 K) of two types of cBN irradiated at ambient temperature with 1.9 MeV electrons. All the samples were small (<1 mm diameter) single crystals of cBN. Three defect centres (with narrow lines at 2.28 eV, 2.15 eV and 1.98 eV) were introduced in both the amber-coloured and blackbrown coloured samples by the irradiation. The amber coloured sample also showed a defect centre (at 1.65 eV) that is present before and after irradiation. Line shape analysis of the zero phonon lines of all three irradiation-induced centres showed that the lines are predominantly Gaussian in character, suggesting that linetype defects such as dislocations are a prevalent characteristic of these crystals. Raman spectroscopy of cBN single crystals as a function of temperature was performed over a wide temperature range from 4 K to 1373 K. The low temperature measurements extended the data previously reported in literature, as this data ranged from room temperature upwards. It was concluded from the shift of Raman peak position with temperature that both linear expansion and anharmonic effects were required to adequately account for the observed data. This is in agreement with previously published findings. Both 3- and 4-phonon processes were required to account for the observed linewidths as a function of temperature, again in agreement with literature. The results presented here and in the associated journal publications illustrate clearly how optical spectroscopy techniques can serve as non-destructive characterisation tools for the mechanical properties of ultra-hard materials.

by Tong Ka Wing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 60-62). / by Tong Ka Wing. / Abstract --- p.1 / Chapter Chapter 1 --- Introduction --- p.2 / Chapter Chapter 2 --- Scattering Intensities and Depolarization Ratios --- p.9 / Chapter Chapter 3 --- Raman Microprobe Experimental Set-up --- p.11 / Chapter 3.1 --- Optical Design of the Raman Microprobe --- p.11 / Chapter 3.1.1 --- Construction of the Olympus BHSM-313U Microscope --- p.11 / Chapter 3.1.2 --- Numerical Aperture of Objectives --- p.13 / Chapter 3.1.3 --- Design of the Raman Microprobe --- p.13 / Chapter 3.1.3.1 --- Design of Signal Collection Optics --- p.16 / Chapter 3.1.3.2 --- Design of Epi-illuminator --- p.17 / Chapter 3.2 --- Performance of the Raman Microprobe --- p.19 / Chapter 3.2.1 --- Collection Efficiencies of Objectives --- p.19 / Chapter 3.2.2 --- Spatial Resolution of the Raman Microprobe --- p.20 / Chapter 3.2.3 --- Rejection of Rayleigh Scattering Light --- p.20 / Chapter 3.2.4 --- Polarization Effect of the Raman Microprobe --- p.22 / Chapter Chapter 4 --- "Sample Preparation, Morphology and Measurements of Spectra" --- p.23 / Chapter Chapter 5 --- Results and Discussion --- p.31 / Chapter 5.1 --- Micro-Photoluminescence of Diamond Films --- p.31 / Chapter 5.2 --- Curve Fitting of Micro-Raman Spectra --- p.34 / Chapter 5.3 --- Part I Micro-Raman of Unoriented Diamond Crystallites --- p.41 / Chapter 5.3.1 --- Diamond Peaks --- p.41 / Chapter 5.3.2 --- D- and G- Peaks --- p.43 / Chapter 5.4 --- Part II Micro-Raman of Oriented Diamond Crystallites --- p.43 / Chapter 5.4.1 --- Diamond Peaks --- p.45 / Chapter 5.4.1.1 --- Depolarization Ratios --- p.45 / Chapter 5.4.1.2 --- Peak Shifts --- p.47 / Chapter 5.4.1.3 --- Peak Widths --- p.48 / Chapter 5.4.2 --- D- and G- Peaks --- p.48 / Chapter 5.4.2.1 --- Depolarization Ratios --- p.48 / Chapter 5.4.2.2 --- Peak Shifts and Widths --- p.48 / Chapter 5.4.3 --- Relation Between Line Width of Diamond Peaks and Intensity Ratios of Diamond Peak to G-Peak --- p.50 / Chapter 5.4.4 --- Internal Stress due to Substrate and Other Growth Defects --- p.52 / Chapter Chapter 6 --- Conclusions --- p.54 / Appendix A --- p.56 / Chapter A.1 --- Scattering Intensities of Diamond --- p.56 / Chapter A.2 --- Scattering Intensities of Graphite --- p.58 / Appendix B --- p.59 / References --- p.60

Thesis (Ph. D.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed Jan. 28, 2010). Additional advisors: Shane A. Catledge, Joseph G. Harrison, Raymond G. Thompson, Uday K. Vaidya. Includes bibliographical references (p. 75-78).

Thesis (Ph. D.)--University of Alabama at Birmingham, 2006. / Additional advisors: Heng Ban, Renato P. Camata, Krishan K. Chawla, Joseph G. Harrison. Description based on contents viewed Feb. 13, 2009; title from PDF t.p. Includes bibliographical references (p. 124-126).