Microstructural Studies by TEM of Diamond Films Grown by Combustion Flame

摘要

Microstructures of diamond films grown in an oxygen-acetylene combustion flamewere studied by Transmission Electron Microscopy (TEM). The O2/C2H2 gas ratio was fixed and the substrate materials and temperature were varied. High quality diamond films were grown by this method. A rough surface and high density of secondary nucleation sites and microtwins were observed in the diamond grains grown on molybdenum (Mo) at a substrate temperature of 500 C. When the substrate temperature was raised to between 600 and 870 C, the defect density was greatly reduced, revealing a low density of stacking faults and dislocations. Near the edge of the diamonds films grown on Mo at 700 C, numerous microtwins were still observed probably indicating a lower growth temperature due to a temperature gradient across the sample surface and flame. Diamond films grown on Si substrates did not show the same substrate temperature dependence on defect density, at least not over the same temperature range. However, the same correlation between defect density, secondary nucleation, and surface morphology was observed.