AC behavior of intrinsic nanocrystalline diamond films

Nanocrystalline diamond was prepared by hot filament assisted chemical vapor deposition technique. The nanometer sized dimension of diamond grains was determined by X-ray line broadening. AC electrical response of deposits, constituted by well formed diamond grains, was studied by admittance spectroscopy at different temperatures. Grain boundary and grain surface were considered different regions able to influence differently the frequency dependent AC response. Observed variations in admittance spectra were attributed to a modification of the grain surface response as frequency and temperature rise. A semiconductor to metal-like transition was evidenced in admittance spectra increasing the frequency of applied signal at lower temperatures.