TWINNING STRUCTURE AND GROWTH HILLOCK ON DIAMOND (001) EPITAXIAL FILM

Surface observation was carried out for diamond homoepitaxial films grown on (001) substrates. Nonepitaxial crystallites and growth hillocks were observed on the films. The majority of the nonepitaxial crystallites were found to be {111} penetration twins, which were considered to originate from the twin nucleation on {111} facet on substrates or epitaxial films. The penetration twins in the configuration of 4-fold symmetry were also observed and they are attributed to the twin nucleation in etch pits on the surface. On the top of the pyramidlike growth hillock, the twinning structure with a pair of parallel {111} twinning planes was observed. The twinning structure is accompanied by a reentrant corner on the surface and induced the enhancement of growth rate, resulting in the formation of growth hillocks.