LASER RAMAN STUDIES OF POLYCRYSTALLINE AND AMORPHIC DIAMOND FILMS

This report describes the results of a number of different, but relate d, laser Raman studies on various CVD diamond samples. It attempts to show the versatility of Raman spectroscopy as a diagnostic tool for th e quality of diamond films, by demonstrating its use in a few novel ap plications. The studies of the laser Raman spectra of amorphic diamond and CVD diamond Films are performed using lasers of different excitat ion wavelength (632.8, 514.5, and 780 nm). For CVD diamond films, a si gnificant reduction in unwanted laser induced fluorescence is observed when using the near-IR diode laser (780 nm) compared to excitation us ing the shorter (visible) wavelengths. The luminescence peak at a Rama n shift of 2260 cm(-1) coinciding with the graphite G band, can be use d as a reliable indicator of poor quality diamond. Additional informat ion about the stress of the diamond films on hard substrates can be ob tained from the intensity of tile luminescence peak at a Raman shift o f 2600 cm(-1). Laser Raman spectra of CVD diamond films that have prev iously been used in electron emission tests show that graphitisation h ad occurred around emission sites. Direct Raman imaging was used to in vestigate the cut, exposed surface of a diamond fibre reinforced metal matrix composite. Amorphic diamond films prepared by laser ablation a re examined by both Raman and transmission electron diffraction, and t he presence of nanocrystalline diamond clusters embedded within the am orphic diamond matrix is verified.