Publication Details

Suzuki, N., Osada, M., Billah, M., Alothman, Z. Abdullah., Bando, Y., Yamauchi, Y. & Hossain, M. A. (2017). Origin of thermally stable ferroelectricity in a porous barium titanate thin film synthesized through block copolymer templating. APL Materials, 5 (7), 076111-1-076111-7.


A porous barium titanate (BaTiO 3 ) thin film was chemically synthesized using a surfactant-assisted sol-gel method in which micelles of amphipathic diblock copolymers served as structure-directing agents. In the Raman spectrum of the porous B aTiO 3 thin film, a peak corresponding to the ferroelectric tetragonal phase was observed at around 710 cm -1 , and it remained stable at much higher temperature than the Curie temperature of bulk single-crystal BaTiO 3 (∼130 °C). Measurements revealed that the ferroelectricity of the BaTiO 3 thin film has high thermal stability. By analyzing high-resolution transmission electron microscope images of the BaTiO 3 thin film by the fast Fourier transform mapping method, the spatial distribution of stress in the BaTiO 3 framework was clearly visualized. Careful analysis also indicated that the porosity in the BaTiO 3 thin film introduced anisotropic compressive stress, which deformed the crystals. The resulting elongated unit cell caused further displacement of the Ti 4+ cation from the center of the lattice. This displacement increased the electric dipole moment of the BaTiO 3 thin film, effectively enhancing its ferro(piezo)electricity.



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