Change in surface morphology of diamond films deposited by DC plasma glow discharge CVD

The influence of the deposition conditions on the morphology of two diamond samples prepared by DC plasma glow discharge CVD has been investigated. A structural change has been observed from a 〈110〉 textured morphology, to the morphology of randomly oriented grains with a heavily disturbed crystalline structure, by decreasing the substrate temperature from 1100 to 950°C. Features of the different morphologies have been studied by SEM and related to the results of Raman spectroscopy and X-ray diffraction. The growth side of the first sample presents cubo-ochtaedral grains with low mutual misorientation while the growth side of the second sample is characterised by ball-shaped structures due to an high density of renucleation on the growing planes, separated by deep interdomain regions. The size of the grains forming the rounded structures decreases gradually towards the bottom of these regions. The poorer crystalline quality of this sample is related to its Raman spectrum, showing an higher luminescence and the presence of graphite-like phases all over the growth surface. Moreover an higher density of defects is evidenced by the higher broadening of the Raman diamond line and of the Bragg diffraction peaks with respect to the textured sample. Analogous results have been reported for a microwave CVD reactor. In this work we confirm the hypothesis that this structural change does not depend on the particular CVD method which are likely to provide the same film quality and morphology at different plasma conditions if the activation of the reactant gases and the surface mobility are in the same range of values.