Preparation and Characterization of Ferroelectric Bi3TiNbO9-Bi4Ti3O12 (m =2–3) Thin Films with Different Superlattice Structures

Abstract

ABSTRACTNatural-superlattice-structured Bi3TiNbO9–Bi4Ti3O12 (m =2–3) (BTN–BIT) films have been grown on Pt/TiO2/SiO2/Si substrates at 400 °C to 550 °C by pulsed laser deposition (PLD) using BTN–BIT (1 mol:1 mol) target, and were post-annealed in O2 for 45 minutes at 750 °C. BTN–BIT films prepared above 500 °C have single phase whose c lattice parameter is estimated to 8.300 nm in consideration of periodicity of lattice structures. This lattice constant is very close to the value (8.316 nm) of that of two unit cells of BTN and one unit cell of BIT, that is 2–1 superlattice structure of BTN–BIT. The BTN–BIT film with 2–1 superlattice structure has large remanent polarization (2Pr = 50 μC/cm2) and large coercive field (2Ec= 350 kV/cm). La-doped BTN–BIT thin film has also large remanent polarization (2Pr = 52 μC/cm2) and relatively small coercive field (2Ec= 220 kV/cm). The La-doped BTN–BIT film is fatigue-free on Pt electrodes up to 1010 switching cycles.