Localization and transfer of charge carriers in CuO nanopowder by impedance spectroscopy

Particular electro-physical characteristics of CuO nanopowder were investigated by impedance spectroscopy using a sensor based on interdigitated structure in the frequency range from 1 Hz to 100 MHz. The results of investigation were considered. Simulation of impedance spectra by equivalent electric circuits was carried out for numerical approximations of the frequency dependences of the dielectrical permittivity and conductivity. Electric charge accumulation of on the boundaries of nanoparticles and near the metal electrodes of the sensor was revealed. It was shown that a double electric layer is formed near the electrodes, which leads to the appearance of anomalously large values of dielectrical permittivity and an increase in the conductivity in the low-frequency region. The obtained results can be explained by proton conductivity in the nanopowder caused by moisture which is adsorbed on the surface of the nanoparticles. It was shown that after high-temperature annealing of CuO nanopowders, accumulation of electric charges was not observed. It was established that hopping or polaron conductivity occurs in the annealed CuO samples, which increases with increasing electric field frequency according to the power law with a fractional exponent.