THE ROLE OF HYDROGEN IN DIAMOND SYNTHESIS FROM CARBON-DIOXIDE HYDROCARBON GASES BY MICROWAVE PLASMA CHEMICAL VAPOR-DEPOSITION

Abstract

We utilized carbon dioxide to replace hydrogen in CO2-(CH4, C2H2, C3H8) gas mixtures and studied the effect on diamond growth of adding a small amount of hydrogen to the system. The deposits were analyzed by scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. Our results showed that diamond film with high growth rate and good crystallinity could be obtained in these systems without supplying additional hydrogen gas. When the amount of hydrogen was increased, all the deposited film in the systems gradually displayed poorer morphology and crystallinity. This indicates that graphitic or amorphous carbon components in the diamond film increased with the addition of hydrogen, with a resulting negative effect on the quality of the diamond film. The influence of hydrogen on diamond growth is also investigated in this study by comparing growth rates and C:H:O ratios among various CO2-(CH4, C2H2, C3H8) systems.