Abstract
ABSTRACTFerroelectric SrBi2Ta2O9 – (Bi4Ti3)1-xNbxO12 (SBT-BTN) multilayer thin films with various stacking periodicity have been synthesized on Ir/Ti/SiO2/Si substrates by metal organic chemical vapor deposition technique (MOCVD). Tributylbismuth [Bi(C4H9)3], strontium-bis[tantal(pentane-ethoxy)(2-methoxyethoxide)] [Sr[Ta(OEt)5(OC2H4OMe)]2], titanium bis(isopropoxy)bis(1-methoxy-2-methyl-2-propoxide) [Ti(OiPr)2(mmp)2] and niobium-ethoxide [Nb(OC2H5)5] were selected as precursors. X-ray diffraction patterns show that the multilayer films annealed at 800°C consisted of a fully formed perovskite phase with polycrystalline structure. The remanent polarization (2·Pr) and coercive field strength (Ec) were 16.2 μC/cm2 and 230 kV/cm, respectively, values which are much higher compared to pure SBT film (2·Pr = 6.4 μC/cm2, Ec = 154 kV/cm).
Highlights
Aurivillius-type structure compounds have been widely investigated by their use in non-volatile ferroelectric memories (NVMs) where they are prepared as thin films [1] [2]
Park [2] found that Bi3.25La0.75Ti3O12 (BLT) thin film annealed at 650 ̊C exhibited a large remanent polarization Pr = 12 μC/cm2
Multilayer structures with alternated layer of SBT and BTN have been prepared on Ir/Ti/SiO2/Si substrate using metal organic chemical vapor deposition technique (MOCVD) technique
Summary
Aurivillius-type structure compounds have been widely investigated by their use in non-volatile ferroelectric memories (NVMs) where they are prepared as thin films [1] [2]. Bismuth-layered-structure ferroelectric materials (BLSF), such as Bi4Ti3O12 (BIT) and SrBi2Ta2O9 (SBT), and different ions substitutions have been studied to improve their fatigue, ferroelectric properties and possibly low polarization switching voltage. Shulman [7] and Villegas [8] reported reduction of conductivity of these films by doping with Nb or W. Such structures as Bi4Ti3O12-SrBi2Ti2O15 (BIT-SBT), Bi3TiNbO9-Bi4Ti3O12 (BTN-BIT), Bi2MoO6-Bi3TiNbO9 (BM-BTN) and Bi2WO6-Bi3TiNbO9 (BW-BTN) have attracted further interest due to their artificially enhanced dielectric, ferroelectric and pyroelectric properties [9]-[14]. Ortega [15] showed dramatically increased remanent polarization (~20.8 μC/cm2) and dielectric constant (~373) in bilayered (SBT/SBN) structures
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