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 di amond samples prepared by DC plasma glow discharge CVD has been invest igated. A structural change has been observed from a [110] textured mo rphology, to the morphology of randomly oriented grains with a heavily disturbed crystalline structure, by decreasing the substrate temperat ure from 1100 to 950 degrees C. Features of the different morphologies have been studied by SEM and related to the results of Raman spectros copy and X-ray diffraction. The growth side of the first sample presen ts cubo-ochtaedral grains with low mutual misorientation while the gro wth side of the second sample is characterised by ball-shaped structur es due to an high density of renucleation on the growing planes, separ ated by deep interdomain regions. The size of the grains forming the r ounded structures decreases gradually towards the bottom of these regi ons. The poorer crystalline quality of this sample is related to its R aman spectrum, showing an higher luminescence and the presence of grap hite-like phases all over the growth surface. Moreover an higher densi ty of defects is evidenced by the higher broadening of the Raman diamo nd line and of the Bragg diffraction peaks with respect to the texture d sample. Analogous results have been reported for a microwave CVD rea ctor. In this work we confirm the hypothesis that this structural chan ge does not depend on the particular CVD method which are likely to pr ovide the same film quality and morphology at different plasma conditi ons if the activation of the reactant gases and the surface mobility a re in the same range of values. (C) 1997 Elsevier Science S.A.