Microstructures of dome-shaped hillocks formed on B doped CVD homoepitaxial diamond films

Various types of harmful growth defects lowering crystal quality are often produced during growth of chemical vapor deposition (CVD) homoepitaxial diamond films. Among these, in this study, microstructures of the dome-shaped hillock (DH) have been studied in details mainly using cross-sectional transmission electron microscopy (TEM). TEM images and selected area electron diffraction patterns indicated that the internal of the DH is composed of single crystal (single domain) diamond whose crystallographic direction is the same as that of the film or the substrate. However, in the internal area of the DHs, there are many dislocations, most of which occur near the boundary regions between the film and the DH and extend to the inside of the DH. In the boundary regions, extra diffraction spots at 1/3 and 2/3 positions in fundamental reflections along [111] directions were observed in the selected area electron diffraction patterns, demonstrating that the boundary regions consist of hybrid structures of parents and twins with common {111} planes. It was also been found that particles (sub mu m in diameter) exist around the interface between the substrate and the film at the bottom of the DHs, strongly suggesting that the DHs nucleate from the particles around the interface.