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Boosting square tensile strain to promote planar ferroelectricity, switchable bias-field, and electro-dielectric memory effect
Speaker: Yoon Seok Oh (UNIST)
The ground states manipulation of complex oxides using heterostructures offers a breakthrough in terms of creating/enhancing advanced functionalities as well as understanding their fundamental nature. For epitaxial heterostructures and free-standing membranes, the feasible materials and physical properties strongly depend on the symmetry and misfit lattice constant of substrates. So far, prevalent perovskite oxide substrates, such as cubic SrTiO3 and orthorhombic R(Al/Sc/Lu)O3 (R = rare earth), have been prominently employed to develop advanced functional heterostructures. However, their congenital symmetry and limited lattice constants circumscribe advances in the functionality and material diversity of the heterostructures. Recently, we found a new substrate of cubic perovskite BaZrO3 to boost square tensile strain and succeeded to synthesize ferroelectric epitaxial films on the BaZrO3 substrate. The lattice constant of BaZrO3 is +8.7 % larger than that of SrTiO3, which enables the application of a very large tensile strength, and the cubic symmetry provides a 4-fold symmetric square lattice on the (001) surface, in contrast to the orthorhombic substrates. It is discovered that oddly uncommon square tensile strain among perovskite substrates coins intriguing physical phenomena. In this talk, we will discuss about the emergent ferroelectric/dielectric properties in the square tensile strained ferroelectric thin film on the BaZrO3 substrate.
Host: Sang-Wook Cheong