Thermodynamic stability of graphitic diamond films produced from catalytic chemical vapour deposition reactor

Thermodynamic stability of synthetic diamond films, produced at 1000–1100 °C from a swirled-continuous Catalytic Chemical Vapour Deposition (CCVD) reactor, is reported. Simple photographs of the as-produced samples displayed several colours that characterize typical beam diffraction spectra of diamond. Raman spectrum revealed a single sharp diamond peak at 1381.4 cm−1 and graphite peaks of 1560 and 1360 cm−1, confirming formation of graphitic carbons and production of graphitic diamond. The quantity of the as-prepared diamond was proportional to the acetylene to hydrogen ratio used in the reactor feed and the apparent proportional relationship between the acetylene and hydrogen ratio and the quantity of diamonds produced only holds at sufficient quantity of acetylene. The synthesized diamond films were unstable at temperature of 90 °C, but displayed phase stability when stored at room temperature in a dark cupboard for 1.5 years. However, presence of impurities in the diamond films negatively affects their thermodynamic stability, and effective purification method to remove the impurities could improve the thermodynamic stability.