Asymmetric switching of ferroelectric polarization in a heteroepitaxial BaTiO3 thin film capacitor

Asymmetric switching of ferroelectric polarization was measured and analyze d for a heteroepitaxial BaTiO3 thin film of 58 nm thickness. The BaTiO3 fil m prepared on a SrRuO3/SrTiO3 substrate by radio-frequency magnetron sputte ring has a c-axis oriented normal to the surface which is 3% longer than th at of the bulk due to lattice misfit between SrRuO3 and BaTiO3. When positi ve and negative voltage pulses of the same amplitude were sequentially appl ied, 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.