Impedance and modulus spectroscopy of nanocrystalline diamond films

Nanocrystalline diamond was prepared by hot filament assisted chemical vapor deposition technique. The ac electrical response of the deposit, constituted by well formed diamond grains and grain boundaries, was studied by impedance spectroscopy technique. Grain boundary and grain surface were considered distinct regions able to influence differently the frequency dependent current transport. Frequency and temperature induced changes in the shape of impedance spectra were attributed to a modification of the grain surface response. A semiconductor to metal-like transition was evidenced in the admittance response, increasing the modulation frequency at the lower temperatures.