Synthesis of Diamond Using In-Liquid Plasma Chemical Vapor Deposition

The synthesis of diamond using in-liquid plasma chemical vapor deposition (CVD) is investigated in this study. Plasma in methanol solution is generated by applying microwave radiation of 2.45 GHz. The composition of the solution and the pressure in the container were varied as experimental parameters. No substrate cooling equipment was required in this process owing to the cooling effect of the liquid itself. The deposits on Si substrates were identified by scanning electron microscopy (SEM) and Raman spectroscopy. A diamond film containing impurities, which was confirmed to have a growth rate of 192 µm/h, was obtained. The deposit had sufficient hardness within the 15 to 80 GPa range, which is suitable for industrial hard coating. Deposition rate increased as system pressure increased, displaying the same tendency of conventional microwave CVD. Optical emission spectroscopy was used to characterize the in-liquid plasma for chemical reaction.