Effect of electrodes on the ferroelectric properties of pulsed-laser ablation-deposited PbZr_XTi_1-xO₃ thin film capacitors

Abstract

PbZr_XTi_1-xO₃ (PZT) thin films have been deposited on a variety of electrode and substrate materials using pulsed-laser ablation-deposition (PLAD). Growth of PZT films on epitaxial (100)Pt/MgO, fiber-textured (111)Pt/Ti/SiO₂/Si, epitaxial (110)RuO₂/MgO₂ or polycrystalline RuO₂/SiO₂/Si resulted in mixtures of perovskite and pyrochlore phases. Under identical growth conditions, films deposited on epitaxial (001)YBa₂Cu₃O_7−δ/MgO and (100)La_0.5CoO₃/MgO, or polycrystalline La_0.5Sr_0.5CoO₃/MgO/Si, contain only the ferroelectric, perovskite phase. The YBa₂Cu₃O_7–δ (YBCO) and La_0.5Sr_0.5CoO₃ (LSC) surfaces stabilize the nucleation of the ferroelectric phase under the PLAD growth conditions. Capacitors with sputter-deposited Pt top electrodes all show significant polarization fatigue by 10⁸ switching cycles, although the (001) PZT films on (100)LSC/MgO and (001)YBCO/MgO show the least degradation. By using PLAD to deposit both top and bottom (100) LSC electrodes, we have obtained LSC/PZT/LSC capacitors on (100) MgO with no observable fatigue after 3×10¹⁰ switching cycles. These results indicate that the LSC/PZT/LSC capacitor structure has promise for use in ferroelectric nonvolatile memory devices.