STRAIN AND MICROSTRUCTURE VARIATION IN GRAINS OF CVD DIAMOND FILM

Cathodoluminescence (CI), Raman spectroscopy and transmission electron microscopy (TEM) have been used to study chemical vapour deposited (CVD) diamond films. Most of this work was carried out on flame-grown CVD diamond film on a silicon substrate. CL was used to identify and map the distribution of defects in films. The CL spectra from cubo-octahedral crystallites of the flame-grown sample showed nitrogen-related 533 nm (2.326 eV) and 575 mn (2.156 eV) systems. The zero-phonon lines were found to be split into two or three components, and by correlation with Raman spectroscopy results the splitting was attributed to a surface tensile stress. A stress variation across crystallites was studied by imaging in each of these components. Below the surface of the crystallite high compressive stresses were detected by Raman spectroscopy. Another sample, grown by hot filament chemical vapour deposition, was studied mainly by TEM in order to elucidate the microstructure of these films. High densities of twins, stacking faults and dislocations were found to be correlated with particular regions of the deposit and to vary in a systematic fashion with distance from the substrate interface. An attempt has been made to present a consistent picture of stress in the cube-octahedral crystals of these samples by relating the results acquired from the different techniques used in this work.