Dielectric Behavior of Diamond Films

Nanostructured diamond films have been synthesized using microwave plasma enhanced chemical-vapor-deposition methods. The dielectric behavior has been investigated by using impedance spectroscopy up to 500%C. Impedance data are preseInted in the form of a Cole Cole plot. It is found that: (i) The resistivity contributed from both the grain iInterior and the grain boundary decreases with an increase of temperature. (ii) Above 250%C, the impurities at grain boundaries are thermally activated, and thus contribute to the dielectric relaxation. (iii) The electrical conductivity of diamond films follows an Arrhenius law with an activation energy transition from 0.13 and 0.67 eV at 250%C. A similar activa- tion energy is found for the Arrhenius plot of relaxation frequencies from 0.14 to 0.73 eV. Possible physical mechanisms responsible for the dielectric behavior are preseInted and discussed.