AC and DC superimposed AC conduction in sodium fluoride thin films

Abstract

The ac and the dc superimposed ac conduction in NaF thin film, deposited between Au thin film electrodes, is studied in situ within the frequency range 300 Hz to 50 kHz, and in the temperature region 300 to 500 K. The dc conduction is non‐ohmic and asymmetric with respect to the diode polarity. Under increasing dc bias, the dielectric loss greatly increases while the high frequency capacitance decreases. The current conduction process in NaF thin film in the observed region of temperature and frequency of measurements is attributed to the cation vacancy movement within the grains and through the grain boundaries, having activation energies (0.84 ± 0.02) eV and (1.12 ± 0.05) eV and pre‐exponential factors in the order of 10−14 s and 10−16 s, respectively. The apparent high dielectric permittivity (103) under low frequency is attributed to the cation vacancy space charge over the dislocation forests at the electrode interface.