Heteroepitaxial growth of diamond thin films on silicon: Information transfer by epitaxial tilting

High resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) have been used to study diamond thin films on silicon. The diamond films were deposited by bits-enhanced microwave plasma assisted chemical vapour deposition. At the interface an amorphous layer of up to several nanometers in thickness was observed to be present over large areas of the interface. In other regions no amorphous interlayer was observed, with the diamond crystallized in direct contact on the silicon (001) surface. In these areas, a 3:2 matching of the two lattices across the interface was established. The angle between the two lattices is small. The suggestion is made that lattice information transfer only occurs at angles at those sites of the 3:2 epitaxy which eliminate misfits (''epitaxial tilting''). However, imperfections in the epitaxial growth, which may be interpreted as growth defects, were observed. These imperfections had no periodic arrangement and are not necessary for this type of epitaxy. The epitaxial tilting is probably favoured by the surface roughness of the silicon substrate inherited from the cleaning procedure. The surface roughness may be in fact a necessary condition for heteroepitaxy. A model for this heteroepitaxial diamond growth on the silicon surface is presented. (C) 1997 Elsevier Science S.A.