FACE-CENTERED-CUBIC CARBON FORMED AT SUBS TRATE CVD DIAMOND FILM INTERFACE

The structure of diamond films grown from a methane and hydrogen gas m ixture by chemical vapor deposition (microwave plasma and hot-filament methods) has been studied with particular attention to the structure of substrate-interface. By examining the diamond films deposited on ei ther Si or Mo by scanning and transmission electron microscopies, elec tron diffraction, and energy dispersive X-ray (EDX) micro-analysis (in -situ), it was found that there is an intermediate layer composed of a morphous carbon and fine particles of face-centered cubic (fcc) carbon between the employed substrate and the deposited diamond film in both cases of Si and Mo. The fine particles of carbon give rise to electro n diffraction rings which satisfy the extinction rule of fcc. The obta ined lattice constant is very close to that of SiC which has a similar extinction rule. However, the fcc carbon and SiC are discernible by e xamining the intensities of their 200 rings of electron diffraction. I t appears that the fcc carbon plays an important role in the diamond n ucleation.