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 (C VD) diamond films. Most of this work was carried out on flame-grown CV D diamond film on a silicon substrate. CL was used to identify and map the distribution of defects in films. The CL spectra from cubo-octahe dral crystallites of the flame-grown sample showed nitrogen-related 53 3 nm (2.326 eV) and 575 mn (2.156 eV) systems. The zero-phonon lines w ere found to be split into two or three components, and by correlation with Raman spectroscopy results the splitting was attributed to a sur face tensile stress. A stress variation across crystallites was studie d by imaging in each of these components. Below the surface of the cry stallite high compressive stresses were detected by Raman spectroscopy . Another sample, grown by hot filament chemical vapour deposition, wa s studied mainly by TEM in order to elucidate the microstructure of th ese films. High densities of twins, stacking faults and dislocations w ere found to be correlated with particular regions of the deposit and to vary in a systematic fashion with distance from the substrate inter face. An attempt has been made to present a consistent picture of stre ss in the cube-octahedral crystals of these samples by relating the re sults acquired from the different techniques used in this work.