AC and DC conductivity studies in pulsed laser ablated (Ba, Sr)TiO₃ thin films

Abstract

A comparison of the ac conductivity of laser ablated (Ba, Sr)TiO₃ thin films was made for films grown at different substrate temperatures. The ac conductivity was studied as a function of frequency and ambient temperature ranging from room temperature to 460° C. Conductivity results from ac and dc measurements were compared in their an respective Arrhenius plots revealing interesting coincidences. The value of the activation energies computed from the Arrhenius plot of à_ac with 1000/T ranged from 0.97 to 1.3 eV in the high temperature region to 0.36 to 0.54 eV in the low temperature region for different samples. The activation energies obtained from pure dc measurement for fields greater than 100 kV/cm across the samples were in the range of 1.06 to 1.32 eV for different samples. The similarity in results suggests a common origin in the de conduction process in the concerned temperature range and was attributed to ionic conduction resulting from oxygen vacancy motion which has been observed to be significant at high temperatures and high fields. For high temperature grown samples the value of activation energy computed from the Arrhenius plots was comparatively less than those grown at lower substrate temperatures. The difference was attributed to the microstructure and the effect of grain boundaries on the motion of oxygen vacancies leading to the conduction process.