Investigation of Diamond-Forming Flames Using Advanced Laser Diagnostics and Laser Enhancement of the Deposition Rate

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Abstract - Lucht and Glumac This is a detailed investigation, both experimental and theoretical, of the chemistry and transport processes in low-pressure diamond-forming flames. The focus is on profiles of temperature and concentrations of radical species near the deposition substrate. Extensive measurements of temperature and of the radical species H (atomic hydrogen), OH (hydroxyl), (atomic carbon), and CH (methyne) are performed for a range of flame pressures, stoichiometries, and total mass flow rates and are compared with numerical flame models. The experimental work is performed in Dr. Robert Lucht's laboratory which has the necessary low-pressure flame apparatus and laser diagnostic equipment; the modeling is done in Dr. Rick Glumac's laboratory. Temperature measurements are made using hydrogen coherent anti-Stokes Raman spectroscopy (H2 CARS). The emphasis in the diagnostic studies is in resolving the gradients in the near-substrate region. A flame model that has been applied successfully in other flame synthesis environments is used. The flame temperature profile and process parameters are used as input, and the model predicts the species profiles; differences between experiment and computation are investigated with a sensitivity analysis to explore the influences of kinetic and transport rates.