Structural and electrical properties of rf magnetron-sputtered Ba1−xSrxTiO3 thin films on indium-tin-oxide-coated glass substrate

Abstract

Structural and electrical properties of rf magnetron-sputtered Ba1−xSrxTiO3 thin films (x=0, 0.25, 0.5, 0.75, 1) on indium-tin-oxide-coated glass substrate were studied. The dense Ba1−xSrxTiO3 thin films sputtered from five different targets at the deposition temperature of 550 °C had individual orientations. The results of compositional analysis in films showed the deviation from the stoichiometry [(Ba+Sr)/Ti=1.009−1.089] with the increase of SrTiO3 content in the targets. The tetragonality in crystallographic structure of Ba1−xSrxTiO3 thin films was not observed even in the case of <x=0.3. The large frequency and composition dependence of ε′ and tan δ were also observed. There were no significant changes in ε′ up to x=0.5; however, the maximum value (ε′=204 at 100 kHz) around x=0.25 was in accordance with the results of bulk Ba1−xSrxTiO3 except at 1000 kHz. Above x=0.5, however, larger decreases of the dielectric constant were observed. The maximum values of ε′ in x=0.25, 0.5, 0.75 were shown around the measuring temperatures of 50, 25, −20 °C, respectively, indicating the diffuse phase transition in Ba1−xSrxTiO3 thin films. The observed increases in ε′ and tan δ above 125 °C are well explained with the barrier model. Nonlinear current-voltage characteristics in Ba1−xSrxTiO3 thin films showed that the lower the SrTiO3 content, the leakier Ba1−xSrxTiO3 thin films became, and the increase of SrTiO3 content leads to the increase of the breakdown fields from 1.7 to 2.7 MV/cm.