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

A comparison of the ac conductivity of laser ablated (Ba, Sr)TiO3 thin film s was made for films grown at different substrate temperatures. The ac cond uctivity was studied as a function of frequency and ambient temperature ran ging from room temperature to 460 degreesC. Conductivity results from ac an d de measurements were compared in their an respective Arrhenius plots reve aling interesting coincidences. The value of the activation energies comput ed from the Arrhenius plot of sigma (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 temperatu re region for different samples. The activation energies obtained from pure de measurement for fields greater than 100 kV/cm across the samples were i n the range of 1.06 to 1.32 eV for different samples. The similarity in res ults suggests a common origin in the de conduction process in the concerned temperature range and was attributed to ionic conduction resulting from ox ygen vacancy motion which has been observed to be significant at high tempe ratures and high fields. For high temperature grown samples the value of ac tivation energy computed from the Arrhenius plots was comparatively less th an those grown at lower substrate temperatures. The difference was attribut ed to the microstructure and the effect of grain boundaries on the motion o f oxygen vacancies leading to the conduction process.