Dependence of the dielectric tunability in Ba(Zr_0.2Ti_0.8)O₃ films deposited on (001) SrTiO₃ substrates on film thickness and temperature

Abstract

BaTiO₃-based ferroelectric family is one of the most studied ferroelectric materials for tunable microwave devices. However, a good tunable material should exhibit low dielectric losses at a high operating frequency and high stability of the dielectric tunability over a wide temperature range, which are conflicting parameters. This study aims to experimentally demonstrate the effects of thickness and temperature on the tunable dielectric properties of epitaxial Ba(Zr_0.2Ti_0.8)O₃ [BZT] films deposited on (100) SrTiO₃ [STO] substrates by the pulsed laser deposition. The crystal structure and electrical properties of the BZT films with different film thicknesses were investigated. Polarization–electric field curves and relative dielectric permittivity–electric field loops (ε_r–E) were measured to characterize the effect of film thickness on the dielectric tunability of the BZT films. Further, the ε_r–E loop was also characterized as a function of temperature. The coercive field decreased with increasing film thickness above 430 nm. The tunability values in the BZT film show little variations with temperature, indicating good temperature stability from −100 to 100 °C. These results show that the BZT film is a promising material for tunable capacitors.