DISLOCATION OF EPITAXIAL CVD DIAMOND AND THE CHARACTERIZATION BY RAMAN-SPECTROSCOPY

Epitaxial diamond thin films were grown on the (100) planes of synthesized type Ib and IIb diamond substrates by the electron-assisted chemical vapor deposition (EACVD) method. The epitaxy was confirmed by reflection high-energy electron diffraction (RHEED) streaky patterns. The etch pits on the surface of the epitaxial thin films on the IIb diamond substrates were identified as edge dislocations by optical microscopy. The etch pit density of dislocation was 4.0 x 10(4) to 3.3 x 10(5) cm-2. In the case of absence of luminescence, epitaxial thin films on the IIb diamond substrate were characterized by Raman spectroscopy. In this experiment, Raman spectra are dominated by signal from the substrate rather than from epitaxial thin film at a thickness of 6000 angstrom. However, a remarkable relation between dislocation density on epitaxial diamond films and first- and second-order Raman spectra of the IIb diamond substrates was found. When an etch pit density of 4.0 x 10(4) cm-2 increased by one order of magnitude, the full width at half maximum (FWHM) of a first-order Raman spectrum broadened by 23% from 1.76 to 2.16 cm-1 at a slit width of 0.8 cm-1. The FWHM of a sharp second-order Raman spectrum also broadened from 5.5 to 5.75 cm-1 at a slit width of 2.0 cm-1. These broadenings of first- and second-order Raman spectra were probably caused by the dislocations in the substrate.