Ferroelectric Properties of Bi1.1Fe1-xCoxO3 Thin Films Prepared by Chemical Solution Deposition Using Iterative Rapid Thermal Annealing in N2 and O2

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Ferroelectric Bi1.1Fe1-xCoxO3 (BFCO) thin films with $x = 0--0.3$ have been prepared on Pt/Ti/SiO2/Si substrates by chemical solution deposition (CSD) using iterative rapid thermal annealing (RTA) in nitrogen and oxygen. The crystallization of the rhombohedral structure of BiFeO3 (BFO) is observed clearly in all thin films, and a monoclinic Bi2O3 phase is also observed and is markedly larger in Co-doped BFO thin films than in BFO thin films. An electric field of 2 MV/cm is applied to the Bi1.1Fe0.9Co0.1O3 thin film annealed in nitrogen at 520 °C without dielectric breakdown, but its polarization versus electric field ($P$–$E$) hysteresis loops are not saturated owing to its high leakage current density. The Bi1.1Fe0.8Co0.2O3 thin film prepared at 520 °C in oxygen shows a very good saturation of $P$–$E$ hysteresis loops at room temperature (RT) at the low leakage current of about $8.7 \times 10^{-3}$ A/cm2 under a high electric field of 1.5 MV/cm. The leakage current at a low electric field may be Ohmic emission at any temperature; however at a high electric field, it may be attributed to tunnel emission at 80 K and Schottky emission at RT.
2010-09-25