Interfacial phases and electrical characteristics of ferreoelectric strontium bismuth tantalate films on Pt/TiO2 and tTi/Pt/Ti heterostructure electrodes

摘要

Strontium bismuth tantalate (SBT) thin films containing Sr defect and Bi excess have been prepared by chemical solution deposition onto spontaneously oxidized Si(100) substrates with two different heterostructure electrodes: Pt/TiO2 and Ti/Pt/Ti. Layered perovskite SBT films were crystallized in oxygen by rapid thermal processing at 973 K for 1 h with an intermediate treatment at 823 K for 2 h. Crystalline phases of the films were monitored by X-ray diffraction analysis with Bragg-Brentano geometry and with grazing incidence. Interfaces developed between the SBT layer and the bottom electrode during thermal treatment were analyzed by X-ray photoelectron and Rutherford backscattering spectroscopies. Chemical composition of the interfaces was dependent on the heterostructure electrode. Interfaces of the SBT films on Pt/TiO2 contain Pt and Bi, whereas those of the films on Ti/Pt/Ti contain Pt, Bi, Ti, and O. Electrical characteristics of these interfaces were deduced from their leakage current behavior. Leakages of SBT films onto Pt/TiO2 are governed by a Schottky emission model at all temperatures, with a barrier height of ∼0.89 eV. Leakages of SBT films onto Ti/Pt/Ti can only be fit to a Schottky model at high temperatures. Despite the so different leakage behavior of the films, their ferroelectric properties and fatigue characteristics are similar, with values of remanent polarization of Pr ≈ 5 μC/cm2 and of the coercive field of E c ≈ 65 KV/cm, and with a ∼20% of reduction of Pr after ∼1010 cycles. These properties are appropriate for their use in nonvolatile memories. © 2005 American Chemical Society.