Strains and cracks in undoped and phosphorus-doped {111} homoepitaxial diamond films

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 and confocal Raman imaging. A distinct Raman peak, broader and 6 cm(-1) lower than the zone-centre optical phonon line of the substrate, was nearly systematically detected showing that in most cases the homoepitaxial layers were under an intense tensile strain. The magnitude of this strain increased with deposited thickness. In the thicker films, it was further observed that a network of oriented cracks could relieve the internal stress. These results suggest that tensile strain is a general feature of defective {111) -oriented CVD diamond homoepitaxial layers. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.