Structural and Electrical Properties of rf Magnetron-Sputtered Ba1-x SrxTiO3 Thin Films on Indium-Tin Oxide-Coated Glass Sbustrate

Abstract

Structural and electrical properties bf 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-degrees-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 epsilon' and tan delta were also observed. There were no significant changes in epsilon' up to x = 0.5; however, the maximum value (epsilon' = 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 epsilon' in x = 0.25, 0.5, 0.75 were shown around the measuring temperatures of 50, 25, -20-degrees-C, respectively, indicating the diffuse phase transition in Ba1-xSrxTiO3 thin films. The observed increases in epsilon' and tan delta above 125-degrees-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.