Nucleation and growth of diamond films on Mo and Cu substrates

Diamond films were grown by hot-filament assisted chemical vapour deposition on polycrystalline Mo and Cu substrates. Mechanisms of nucleation and growth of diamond were observed to be different on Mo and Cu. X-ray diffraction results showed that an interfacial layer of Mo2C was formed on Mo and diamond grew on this carbide layer. However, when diamond was grown on Cu in identical conditions diamond crystallites had a very low nucleation density, therefore continuous films were never observed. In order to enhance the nucleation density and improve growth of diamond films on Cu a multi-step process was employed. The Cu substrates were first scratched (or seeded) with diamond powder and then annealed. The filament power was increased to melt the surface of the Cu substrate momentarily and immediately after melting, the substrate temperature was rapidly lowered to the regular diamond deposition temperature for growth. The annealing and melting process together with scratching (or seeding) was very effective for achieving enhanced nucleation density and consequently obtaining thick and continuous diamond films. The diamond films were characterised by scanning electron microscopy, X-ray photoemission spectroscopy and Raman spectroscopy. A model for enhanced nucleation density and growth of diamond on Cu is suggested based on our experimental results.