Transmission electron microscopy (TEM), transmission electron diffraction (TED), atomic force microscopy (AFM), and scanning electron microscopy have been used to investigate the initial nucleation process and growth behavior of diamond films by microwave plasma chemical vapor deposition. TED examination revealed epitaxial relations between the β-SiC and the Si, and the diamond and the β-SiC, which depended on the bias-enhanced nucleation (BEN) time and methane (CH4) concentration. The highly oriented (001) diamond films were obtained after 25 min BEN for 4% CH4 and 20 min BEN for 8% CH4. TEM revealed the β-SiC crystallites 2-25 nm across and the diamond crystallites 3-40 nm in size which depended on the CH4 concentration and the BEN time. As the BEN time increased, the density of the β-SiC cyrstallites increased from ∼2.7 × 1011 to ∼3.4 × 1012 cm2, while that of the diamond crystallites varied from ∼2.0 × 109 to ∼4.0 × 1010 cm-2. Discrepancy between the densities obtained using TEM and AFM is discussed. It is shown that the heteroepitaxially oriented diamond crystallites are critically important for the growth of the highly (001)-oriented diamond films, although the heteroepitaxially oriented β-SiC crystallites could serve as nucleation sites for the growth of the diamond films.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry