Internal stresses in {111} homoepitaxial CVD diamond

Undoped and phosphorus-doped diamond thin films grown by microwave plasma-enhanced chemical vapour deposition (MPCVD) on Ib {111}-oriented diamond substrates have been studied by confocal micro-Raman spectroscopy. Thanks to the confocal optics, the Raman signal arising from the epilayer could be discriminated from that arising from the substrate. In this study, a distinct Raman peak, broader and approximately 6 cm(-1) lower than the optical phonon line of the substrate, was systematically detected and showed that the homoepitaxial layers were under an intense tensile stress. The magnitude of this stress increased with deposited thickness up to a few GPa. In the thicker films, a high compressive stress was also detected at the substrate near surface. Finally, it was observed that a network of oriented cracks could relieve the internal stress. (C) 2003 Elsevier B.V. All rights reserved.