Coalescence and overgrowth of diamond grains for improved heteroepitaxy on silicon (001)

Heteroepitaxial (001)-oriented diamond films with considerably increased lateral grain size and strongly improved orientational perfection could be prepared by microwave plasma-assisted chemical vapor deposition using a (001)-textured growth process on Si (001) subtrates followed by a (110) step-flow growth process. The diamond films were characterized by atomic force microscopy, scanning electon microscopy, and transmission electon microscopy. The results indicate that the diamond crystals increase their lateral dimensions at the (001) film surface either by coalescence of grains combined with a termination of the propagation of grain boundaries or by changing the grain boundary plane orientations from preferentially vertical to preferentially parallel directions with respect to the (001) growth faces. In the second case, the grains with relatively large angle deviation from the ideal epitaxial orientation are overgrown by those with relatively small angle deviation.