Nanocrystalline diamond films were synthesized by microwave plasma-enhanced chemical vapor deposition using Ar/H_(2)/CH_(4) gas mixtures. A Fluke PM6306 RCL meter was used to study the electrical impedance of these diamond films in the frequency range 50 Hz to 1 MHz. The impedance dispersion measurement yields the real and imaginary parts in the form of a Cole-Cole plot in the complex plane. A single semicircular response of the impedance of nanocrystalline diamond films was observed at temperatures below 250℃, with a second semicircular response appearing at low frequencies at temperatures above this. The semicircular responses were found to fit a double resistor-capacitor parallel circuit model. Physical mechanisms likely to be responsible for these observations are discussed in this paper.
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