Composition and electrode effects on the electrical properties of SrBi₂Ta₂O₉

SrBi₂Ta₂O₉ has attracted great interest for non-volatile memory applications due to its minimal polarization fatigue. This paper describes systematic studies, using pulsed laser deposition, on the effect of deposition conditions on the Bi-Pt reaction and on the potential for low temperature processing. Changing the deposition temperature (T_s) and oxygen gas pressure during deposition can control the Bi content in the films. At a T_s of 600°C, the films have excess Bi and do not fully crystallize to SBT, resulting in poor remnant polarization (P_r). These films consist mostly of the pyrochlore phase, plus a small amount of disordered, c-oriented layered perovskite SBT. By annealing over 750°C, the films show improved P_r, but further Pt - Bi interactions occur. At a T_s of 700°C, the as-deposited films are fully crystallized and show saturated hysteresis loops. However, Bi deficiency through alloying results in reduced remnant polarization (2P_r = 7.0 μC/cm²). Films on Ir/Pt show reduced electrode reactions and improved properties.