Raman microscopy has been employed to investigate the nature of damage created when natural type-IIa diamond is irradiated with MeV alpha particles. Three features appear in the Raman spectrum due to damage, viz., (i) the first-order diamond Raman line is broadened and downshifted, (ii) broad features appear which are a measure of the vibrational density of states of ion-beam-amorphized diamond, and (iii) the damage causes the appearance of sharp defect-induced Raman peaks at 1490 and 1630 cm-1. For damage below an amorphization threshold, a linear relationship exists between the full width at half maximum and frequency shift, which shows that these are Kramers-Kronig related. The annealing behavior of the sharp Raman feature at 1490 cm-1 suggests that this peak is associated with vacancies with an activation energy for annealing of 4.06 eV, while the 1630-cm-1 peak is due to an interstitial related defect with an activation energy of 1.2 eV. For sub-MeV ion irradiation, damage beyond the critical amorphization level usually leads to relaxation of the diamond structure to graphite upon thermal annealing. However, for MeV ion irradiation, it was found that annealing, even when the ion induced damage level is well above the amorphization threshold, could restore the original diamond structure. We attribute this result to the high internal pressure the damaged layer is subjected to which does not allow relaxation to graphitically bonded structures.

Raman investigation of damage caused by deep ion implantation in diamond

Diamond coatings on cemented tungsten carbide tools by low-pressure microwave CVD

Low pressure microwave plasma assisted chemical vapor deposition (MPCVD) of diamond coatings on silicon nitride cutting tools

Nanocrystalline diamond/β-SiC composite film system has been realized as an interlayer for the deposition of continuous and adherent diamond thin films on W and Mo substrate materials by microwave plasma chemical vapor deposition (MWCVD) technique in a single process step using a gas mixture of H2, CH4, and tetramethylsilane [Si(CH3)4, TMS]. Continuous and high quality diamond film growth on the interlayers was clearly evident. Scanning electron microscopy, X-ray diffraction and micro Raman scattering studies have been carried out to study the surface morphology and the crystal structure of the deposited films. The composite films consist of mainly two phases that of diamond and β-SiC. Content of β-SiC in these films can be varied by varying the concentration of TMS in the gas phase reaction. Diamond top layers on different composite interlayers are found to be possessing low residual stress values and simple Brinell indentation tests showed an improved adherence of these top layers in comparison to those deposited directly on the pre-treated substrates. Even the homogeneous composite (i.e., without the diamond top layers) as well as the gradient composite interlayers when considered as separate thin film systems, showed a very good adherence.

Nanocrystalline diamond/β-SiC composite interlayers for the deposition of continuous diamond films on W and Mo substrate materials

Laser desorption–ionization time of flight mass spectrometry of various carbon materials

Production and characterisation of amorphic diamond films produced by pulsed laser ablation of graphite

This report describes the results of a number of different, but related, laser Raman studies on various CVD diamond samples. It attempts to show the versatility of Raman spectroscopy as a diagnostic tool for the quality of diamond films, by demonstrating its use in a few novel applications. The studies of the laser Raman spectra of amorphic diamond and CVD diamond films are performed using lasers of different excitation wavelength (632.8. 514.5, and 780nm). For CVD diamond films, a significant reduction in unwanted laser induced fluorescence is observed when using the near-IR diode laser (780 nm) compared to excitation using the shorter (visible) wavelengths. The luminescence peak at a Raman shift of 2260 cm -1 coinciding with the graphite G band, can be used as a reliable indicator of poor quality diamond. Additional information about the stress of the diamond films on hard substrates can be obtained from the intensity of the luminescence peak at a Raman shift of 2600 cm -1 . Laser Raman spectra of CVD diamond films that have previously been used in electron emission tests show that graphitisation had occurred around emission sites. Direct Raman imaging was used to investigate the cut, exposed surface of a diamond fibre reinforced metal matrix composite. Amorphic diamond films prepared by laser ablation are examined by both Raman and transmission electron diffraction, and the presence of nanocrystalline diamond clusters embedded within the amorphic diamond matrix is verified.

Laser Raman Studies of Polycrystalline and Amorphic Diamond Films

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Production and characterisation of amorphic diamond films produced by pulsed laser ablation of graphite

Laser Raman Studies of Polycrystalline and Amorphic Diamond Films