Micro-Raman fingerprint of grain boundary in [100] oriented diamond films: Stress distribution and diamond phases

Local distribution of stress state and carbon bonding in diamond films are studied by micro-Raman spectroscopy. Large changes in intensity, line shape, and peak position of the diamond Raman line occur close to the grain boundary. The characteristic feature of such region is a 1326 cm(-1) Raman peak, whose detection suggests that defect incorporation at the grain boundary may promote a diamond symmetry modification from a cubic to hexagonal one. Close to intergrain locations, large anisotropic stresses also induce frequency splitting of the Raman line. Suitable stress configurations consistent with the detection of an almost unshifted component and of a largely frequency-changing mode are analyzed. (C) 1998 American Institute of Physics. [S0003-6951(98)02635-7].