Asymmetric Switching of Ferroelectric Polarization in a Heteroepitaxial BaTiO 3 Thin Film Capacitor

Asymmetric switching of ferroelectric polarization was measured and analyzed for a heteroepitaxial BaTiO 3 thin film of 58 nm thickness. The BaTiO 3 film prepared on a SrRuO 3 /SrTiO 3 substrate by radio-frequency magnetron sputtering has a c -axis oriented normal to the surface which is 3% longer than that of the bulk due to lattice misfit between SrRuO 3 and BaTiO 3 . When positive and negative voltage pulses of the same amplitude were sequentially applied, asymmetric responses were observed in the transient current. Although the switching charge densities Q sw were the same for both the polarities, the switching time t s was longer and the peak current i max was smaller for the positive response. From the analyses of the transient current, the asymmetric switching of polarization was attributed to the discrepancy in coercive voltages V c between polarities.