An admittance spectroscopy study of grain and grain boundary of diamond

AC electrical response of polycrystalline diamond films, prepared by hot-filament assisted chemical vapor deposition technique, was studied by admittance spectroscopy. Temperature dependent admittance evidenced two main exponential regimes associated with distributions of traps within diamond grains and at grain boundaries, respectively. Activation energies of the low-frequency conductance and of the characteristic relaxation frequency from Jonscher equation also evidence two trap levels associated to grain and grain boundary. This picture is supported by capacitive contributions obtained from imaginary part of electric modulus spectra, furthermore suggesting the presence of charge carriers tunneling at the Fermi level. Results are discussed in terms of a schematic band energy diagram.