Two kinds of Cu substrates were used to grow diamond films,one of them being 99.99% polycrystalline Cu foil and the other 99.95% phosphorus deoxidized Cu foil.Large-area,free-standing polycrystalline diamond films were obtained by hot filament CVD on both substrates.The diamond films on the two kinds of Cu substrates were comparatively investigated by high resolution optical microscopy,scanning electron microscopy,Raman spectroscopy,and X-ray diffraction.The quality of films on deoxidized Cu are not worse than that on polycrystalline Cu,while the nucleation densities ,growth rate and stress in film on deoxidized Cu is higher than those on polycrystalline Cu.It is indicated that the annealing process and optimized growth conditions must be used to obtain large-area continuous diamond films.
In nucleation process of thin film growth, stable clusters will gradually cover substrate surface. The growth will occur in the covered parts of substrate, and the nucleation will proceed in the uncovered parts. In this paper, we investigate the influence of coverage on nucleation and growth of thin films and give a series of revised formulae for the widely used theory of thin film growth. We get that the nucleation rate is proportional to the square of uncovered area. It looks rough that the nucleation rate is considered to be a constant in thin film theories.
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