Nucleation and growth of diamond using a computer-controlled oxy-acetylene torch
A computer-controlled oxy-acetylene torch was used to nucleate and grow polycrystalline diamond films. The computer interface was designed to monitor and or modify continuously oxygen and acetylene flow rates, while a PID temperature controller was used to stabilize the substrate temperature at selected set points. This system significantly enhanced the control and reproducibility of the diamond growth, leading to increased area (50 mm2), high quality diamond films. A pretreatment was used to enhance the nucleation of diamond. This pretreatment involved an oxygen-to-acetylene ratio of 0.93-0.95, with the substrate about 15 mm from the torch nozzle. Surface analysis revealed that diamond was deposited in as little as 30 s with a significant amount of carbon being incorporated in the sp2 form. When the substrate was subsequently moved up into the flame and the oxygen-to-acetylene ratio was increased, good quality diamond was observed to deposit on the pretreated area over the entire area of the flame front. Utilizing computer control, systematic and complex variations in gas chemistry could be applied during growth. Thus, the oxygen-to-acetylene ratio was modified between 0.97 and 1.01 using a sawtooth function, resulting in larger grain sizes relative to normal growth conditions, with very little sp2 bonding.
von Windheim, JA; Sivazlian, F; McClure, MT; Glass, JT; Prater, JT
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