Diamond synthesis under atmospheric pressure from ethanol-water solution using hot-filament chemical vapor deposition method assisted by electrospray

摘要

The effect of water on diamond synthesis was investigated in the hot-filament chemical vapor deposition process under atmospheric pressure. We adopted an ethanol-water-hydrogen system; an ethanol-water mixture was supplied by an electrospraying technique. With increasing the water content, the morphology of deposited diamond varied from mirror-ball-like to small-crystalline particles. Dense diamond films with distinct facets were obtained at 5.58 mol % ethanol with 1.39 mol % water and 5.27 mol % ethanol with 2.26 mol % water. In Raman spectroscopy, the full width at half maximum (FWHM) of the diamond peak at 1333 cm~(-1) decreased with the water content and a broad peak of nondiamond carbon around 1550 cm~(-1) was markedly reduced. The FWHM also decreased by lowering the ethanol concentration in an ethanol-hydrogen system. Only the ethanol-water-hydrogen system yielded the high-quality diamond with a relatively high deposition rate. The major roles of water were cleaning the filament and removing nondiamond carbon in the deposit with the water-gas reaction, H_2O + C→H_2+CO.