High resolution transmission electron microscopy study of diamond films grown from fullerene precursors

High-resolution transmission electron microscopy (HRTEM) has been used to investigate the microstructure of diamond films grown by plasma-assisted chemical vapor deposition using fullerene precursors. HRTEM observations of as-grown films revealed an array of larger crystals (>200 nm) within a polycrystalline matrix of much smaller crystallites (<20 nm). The randomly oriented small crystallites were nearly free of structural imperfections such as stacking faults or twins, while the larger ones had preferred <110> orientations with respect to the Si (100) substrate and showed evidence of structural defects on the periphery of the crystals. The most common defects were V-shaped {Sigma}9 twin boundaries, which are generally believed to serve as re-entrant sites for diamond nucleation and growth. The observation of growth steps on both (111) and (110) surfaces seems to support a reaction model in which fragments of C{sub 60}, including C{sub 2}, are considered the growth species. In particular, the nanocrystallinity of the films is most likely due to a high carbon cluster density from C{sub 60} fragmentation at or near the diamond surface, which can serve as nucleation sites for the growth of new crystallites