Growth, structure, and properties of all-epitaxial ferroelectric (Bi,La)4Ti3O12∕Pb(Zr0.4Ti0.6)O3∕(Bi,La)4Ti3O12 trilayered thin films on SrRuO3-covered SrTiO3(011) substrates

All-epitaxial (Bi,La)4Ti3O12(BLT)∕Pb(Zr,Ti)O3(PZT)∕(Bi,La)4Ti3O12 trilayered ferroelectric thin films were prepared on SrRuO3 (SRO)-covered SrTiO3(011) substrates by pulsed-laser deposition. Epitaxial relationships were identified to be BLT(118)‖PZT(011)‖SrTiO3(011), and BLT[1¯1¯0]‖PZT[100]‖SrTiO3[100]. Atomic force microscopy observation of the surface showed that the upper BLT layer is composed of rod-like grains. Cross-sectional transmission electron microscopy investigations revealed ferroelectric 90° domains in the PZT layer, as well as a rather smooth morphology of the BLT/PZT interfaces. Remanent polarization and coercive field of the trilayered films were 28.1μC∕cm2 and 33.7kV∕cm, respectively. The thin films showed a high fatigue resistance at least up to 1010 switching pulse cycles. Obviously, a trilayered structure combines the advantages of PZT and BLT, indicating that the all-epitaxial BLT/PZT/BLT trilayered structure is a promising material combination for ferroelectric memory device applications.