CHARACTERIZATION AND MORPHOLOGICAL FEATURES OF DIAMOND FILMS AND PARTICLES AFFECTED BY A DIAMOND-LIKE PRECOATED LAYER

Abstract

Submicron polycrystalline diamond films and spherical agglomerated diamond particles were deposited from a CH4-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 ball-like particles of amorphous carbon with numerous diamond microcrystals were deposited on an Si substrate using a high CH4 concentration (7, 9 and 11 vol.%). Then the CH4 concentration was lowered to 0.6 vol.%, so that a surface layer of collective idiomorphic finer diamond crystals (less than 1 mum) grew on the pre-coated layer and ball-like particles. The surface roughness of the diamond films was 0.02 mum, 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 CH4 in the first step. The diamonds were characterized using scanning electron microscopy observations, X-ray diffraction, and Raman and cathodoluminescence spectral analysis.