Dielectric dynamics of the polycrystalline Ba0.5Sr0.5TiO3 thin films

Polycrystalline Ba0.5Sr0.5TiO3 films, with thicknesses between 90 and 600 nm, were prepared on alumina substrates at 900 degrees C by chemical solution deposition (CSD) and a dielectric spectroscopy investigation of the in-plane properties was performed. The 5-kHz permittivity epsilon' shows a non-monotonic thickness dependence, reaching 1230 at room temperature for the 310-nm-thick film, whose grain size is similar to 75 nm. Its 15-GHz-value and losses are 1105 and 0.05, respectively. The temperature of the permittivity maximum T-max at 5 kHz decreases with increasing thickness from 277 to 250K for the 170- and 600-nm-thick films, respectively, which has been linked to the residual biaxial stress. A hysteresis is observed in the permittivity epsilon'-electric field E-DC characteristics in all the films up to similar to 50K above T-max. Frequency dispersion in which permittivity decreases with increasing frequency is present below T-max in films thicker than 90 nm. The high permittivity values of the thinnest films, which are among the highest reported in the (Ba,Sr)TiO3 films with grain sizes below 75 nm, are a direct proof of the optimized CSD processing conditions. Copyright (C) EPLA, 2016