Characterization and morphological features of diamond films and particles affected by a diamond-like pre-coated layer

Abstract

Submicron polycrystalline diamond films and spherical agglomerated diamond particles were deposited from a CH 4-H 2 gas system by microwave plasma-enhanced chemical vapour deposition. In the studies on promoting the nucleation density of diamonds reported here, it was found that spherical agglomerated diamond particles and smooth-surface films could be obtained through a two-step process. In the first step, a pre-coated layer and bill-like particles of amorphous carbon with numerous diamond microcrystals were deposited on a Si substrate using a high CH 4 concentration (7, 9 and 11 vol.%). Then the CH 4 concentration was lowered to 0.6 vol.%, so that a surface layer of collective idiomorphic finer diamond crystals (less than 1 υm) grew on the pre-coated layer and ball-like particles. The surface roughness of the diamond films was 0.02 υm, which was clearly less than that of the diamond film grown directly on the Si substrate. The morphology of agglomerated diamond particles was significantly affected by the concentration of CH 4 in the first step. The diamonds were characterized using scanning electron microscopy observations, X-ray diffraction, and Raman and cathodoluminescence spectral analysis.