Polycrystalline diamond films were synthesized using an oxy-acetylene flame in the open atmosphere and in an enclosed chamber. In the present work, we have shown that the 2.16eV defect band seen in the photoluminescence spectra from the central portion of the films grown in the open atmosphere show a dependence on the growth temperature. Films grown in the open atmosphere all exhibit a decrease in the crystalline quality when moving to the outside edge most likely due to the entrainment of nitrogen into the films.
The present study was done in the enclosed chamber using an oxygen atmosphere via an oxygen flow around the torch. Films have been grown in the enclosed chamber that show only trace amounts of the 2.16eV band. Both the Raman and the photoluminescence spectra show that the films grown in the enclosed chamber are very uniform over the deposition area, which suggests that the degradation of the outer portion of the open atmosphere films may be the result of room air entrainment, and not a temperature variation across the substrate. In addition, when either lower purity oxygen is used or lower growth temperatures, we easily observe the 2.16eV band which may be the result of nitrogen impurities in the source gases.