EPITAXIAL FERROELECTRIC THIN-FILMS FOR MEMORY APPLICATIONS

Epitaxial ferroelectric Pb0.9La0.1Zr0.2Ti0.8O3 (PLZT) thin film capacitors with perovskite metal oxide electrodes (such as YBa2Cu3O7) were grown on single-crystal LaAlO3 and on buffered [100] Si. Structural studies using X-ray diffraction and transmission electron microscopy show that the PLZT layer is free of large-angle grain boundaries (i.e. it is single crystal like). Chemical analysis by Rutherford backscattering shows the composition of the PLZT layer to be close to that of the target. Ferroelectric hysteresis measurements using both pulsed measurements and a variable frequency Sawyer-Tower circuit yield remnant polarization values (at 5 V)in the range 10-30 mu C cm(-2) (depending on deposition conditions) with a coercive field in the range 35-80 kV cm(-1). These heterostructures also show excellent resistance to bipolar fatigue, aging and logic state retention characteristics.