Epitaxial Ferroelectric Aurivillius-Type Phases on Metallic Oxides by Pulsed Laser Deposition

Abstract

ABSTRACTBi-based layered perovskites, also called Aurivillius-type phases, are superior to simple perovskite materials with regard to their ferroelectric long-term stability. Another way to alleviate fatigue and aging problems in metal-ferroelectric-metal (MFM) heterostructures is to replace the bottom metallic electrode with a conductive oxide electrode. An attempt to combine the two approaches has been made to investigate whether a further improvement in stability can be achieved. To promote an oriented growth of the ferroelectric films, epitaxial buffer layers (YSZ, Ce02) and epitaxial electrodes of (La0.5Sr0.5 )Co03 (LSC) have been consecutively deposited onto Si (100). Finally a ferroelectric thin film of the layered perovskite Bi4Ti3012 (BiT) has been grown. Rocking curve measurements demonstrate good epitaxial growth of both the buffer and the electrode layers. The ferroelectric thin films show a preferred c-axis orientation. Cross-section TEM images reveal a twinned superstructure in the LSC layer with a tripling of the lattice parameter. EDX line-scans show that a Co-enriched and Bi-depleted layer had formed at the BiT/LSC interface. After deposition of Au electrodes on both the BiT and the LSC layer, a hysteretic behavior could be detected and the ferroelectric properties of the c-oriented BiT film be confirmed.