Nanocrystalline diamond films have been successfully synthesized on plastic substrates at substrate temperatures below $100°\text{C}$ using a microwave plasma chemical-vapor deposition technique. This has been realized by using low reaction-gas pressures and a surface-wave plasma with a low-electron temperature over the growth region. The nanocrystalline diamond films exhibit growth rates with much lower temperature dependence than conventional diamond growth and decreasing nucleation rates with increasing substrate temperatures. These phenomena imply a different growth mechanism from conventional diamond syntheses. In addition, our analysis on the crystal size distribution of the nanocrystalline diamond film indicates the possibility of diamond nucleation in a stable phase in the plasma. The gas-phase nucleation, invoked by the low-electron temperature of the surface-wave plasma, well explains the low-temperature growth and the temperature dependences of the growth rate and the nucleation rate.

• Received 2 April 2010

DOI:https://doi.org/10.1103/PhysRevB.82.125460

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