Nucleation and initial growth of diamond film on Si substrate

A high resolution electron microscopic (HREM) study of interface structure between diamond film and its silicon substrate is presented. The HREM images reveal that there is an amorphous intermediate layer between the diamond film and its substrate for samples grown by hot filament chemical vapor deposition (HF-CVD). In some cases, β-SiC crystallites and a few graphite microcrystallites may be embedded in this amorphous layer. The HREM images obtained from cross-sectional specimens reveal that the diamond crystallites nucleate directly either on the amorphous intermediate layer, at diamond seed crystallites that were left during pretreatment of Si substrate by diamond paste,β-SiC particles, or at some scratches of the Si substrate. HREM images also reveal that the quantity, distribution, and the size of β-SiC particles in the intermediate layer are different for different processes. Some β-SiC crystallites have certain orientation relationships with the Si substrate. A HREM study of cross-sectional specimens indicates that twins and microtwins in the HF-CVD diamond film are formed during nucleation of the film either from diamond seeds, β-SiC crystallites, or the amorphous intermediate layer. Multiple twins formed from different β-SiC crystallites have also been observed. High densities of “V” shaped microtwins formed during the initial growth of the diamonds and the formation mechanism of these twins are discussed.