HOMOEPITAXIAL C-13 DIAMOND FILMS STUDIED BY MICRO-RAMAN AND PHOTOLUMINESCENCE SPECTROSCOPY

Raman microscopy has been used to study C-13 and C-12/C-13 isotopicall y mixed homoepitaxial diamond films grown by chemical vapor deposition on natural diamond substrates. The measured dependencies of the frequ ency and the width of the first-order zone-center optic phonon line on the isotope composition agree well with those reported for diamond cr ystals synthesized under high pressure. To study the evolution of the epitaxial layer quality for a C-13 diamond film grown on a natural typ e IIa diamond substrate with an isotopic composition of almost pure C- 12, micro-Raman spectroscopy has been performed on a polished cross se ction. The width of the zone-center phonon line is found to increase i n the epitaxial layer from 2.6 up to 3.0 cm-1 with increasing distance from the film/substrate interface and is thus consistently larger tha n the linewidth of 2.5 cm-1 measured in the substrate. Two photolumine scence bands are observed in the epitaxial film centered at 2.16 and 2 .21 eV. The 2.16 eV band, which has been attributed to emission from a n interstitial nitrogen-vacancy complex, shows a pronounced maximum in intensity at the film/substrate interface indicating an enhanced nitr ogen incorporation at the interface.