ASYMMETRIC SWITCHING AND IMPRINT IN (LA,SR)COO3 PB(ZR,TI)O-3/(LA,SR)COO3 HETEROSTRUCTURES/

(La,Sr)CoO3/Pb(Zr,Ti)O-3/(La,Sr)CoO3 (LSCO) heterostructures have been grown on LaAlO3 substrates by pulsed laser deposition (PLD) to invest igate asymmetric polarization switching of Pb(Zr,Ti)O-3 (PZT) thin fil ms with different electrode configuration. P-V hysteresis loop of LSCO /PZT/LSCO was symmetric. However, LaCoO3 (LCO)/PZT/LSCO showed a large ly asymmetric P-V hysteresis loop and large relaxation of the remanent polarization at the negatively poled state, which means that the nega tively poled state was unstable. On the other hand, LSCO/PZT/LCO exhib ited large relaxation of the positively poled state. The asymmetric be havior of the polarized states implies the presence of an internal ele ctric field inside the PZT layer. It is suggested that the internal el ectric field caused by built-in voltages at LCO/PZT and LSCO/PZT inter faces. The built-in voltages at LCO/PZT and LSCO/PZT interfaces were 0 .6 eV and 2.1 eV, respectively.