BUILT-IN VOLTAGES AND ASYMMETRIC POLARIZATION SWITCHING IN PB(ZR,TI)O-3 THIN-FILM CAPACITORS

Asymmetric polarization switching of Pb(Zr,Ti)O-3 (PZT) thin films wit h different electrode configuration has been studied in (La,Sr)CoO3/Pb (Zr,Ti)O-3/(La,Sr)CoO3 (LSCO) heterostructures in which the conducting oxide (La,Sr)CoO3 and/or LaCoO3 (LCO) have been used as an electrode. Polarization-voltage (P-V) hysteresis loop of LSCO/PZT/LSCO was symme tric. However, LCO/ PZT/LSCO showed a largely asymmetric P-V hysteresi s loop and large relaxation of the remanent polarization at the negati vely poled state, eventually leading to an imprint failure. On the oth er hand, LSCO/PZT/LCO exhibited large relaxation of the positively pol ed state. The asymmetric behavior of the polarized states implies the presence of an internal electric field inside the PZT layer. It is sug gested that the internal electric field is caused by built-in voltages at LCO/PZT and LSCO/PZT interfaces. The built-in voltages at LCO/PZT and LSCO/PZT interfaces were 0.6 V and 0.12 V, respectively. (C) 1998 American Institure of Physics. [S0003-6951(98)04625-7].