Plasma-enhanced synthesis of diamond nanocone films

Three DC plasma processes in a hot filament reactor were developed to synthesize nanostructured carbon films: (1) pure hydrogen plasma treatment of diamond films pre-coated on silicon substrate (2) plasma-enhanced hot filament chemical vapor deposition (HFCVD) with a gas mixture of hydrogen and methane and (3) graphite etching in a pure hydrogen plasma. Highly aligned diamond nanocone films were synthesized on silicon substrates pre-coated with diamond films in all three processes. When the silicon substrates were pre-deposited with sparsely distributed diamond particles, diamond and graphitic nanocones were grown simultaneously on substrate areas with and without pre-deposited diamond particles, respectively in the last two processes. All the nanocones have nanometer-size tips and sub micrometer-size roots and are highly aligned with various orientation angles influenced by the direction of the electric field lines near the sample surface. In comparison with the conventional method using a methane and hydrogen mixture, it is found that diamond nanocones synthesized by graphite etching have one order of magnitude higher cone density, lower sp 2 carbon content and grow four times faster