title: Atomic scale imaging of competing polar states in a Ruddlesden-Popper layered oxide.
abstract: Layered complex oxides offer an unusually rich materials platform for emergent phenomena through many built-in design knobs such as varied topologies, chemical ordering schemes and geometric tuning of the structure. A multitude of polar phases are predicted to compete in Ruddlesden-Popper (RP), An+1BnO3n+1, thin films by tuning layer dimension (n) and strain; however, direct atomic-scale evidence for such competing states is currently absent. Using aberration-corrected scanning transmission electron microscopy with sub-Ångstrom resolution in Srn+1TinO3n+1 thin films, we demonstrate the coexistence of antiferroelectric, ferroelectric and new ordered and low-symmetry phases. We also directly image the atomic rumpling of the rock salt layer, a critical feature in RP structures that is responsible for the competing phases; exceptional quantitative agreement between electron microscopy and density functional theory is demonstrated. The study shows that layered topologies can enable multifunctionality through highly competitive phases exhibiting diverse phenomena in a single structure.
authors: Department of Materials Science and Engineering and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors: Greg
authors: G
authors: Stone
authors: National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors: Colin
authors: C
authors: Ophus
authors: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis 55455, USA.
authors: Turan
authors: T
authors: Birol
authors: National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors: Jim
authors: J
authors: Ciston
authors: Department of Materials Science and Engineering and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA.|Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA.
authors: Che-Hui
authors: CH
authors: Lee
authors: Materials Characterization Laboratory, Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors: Ke
authors: K
authors: Wang
authors: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors: Craig J
authors: 0000-0002-7567-6895
authors: CJ
authors: Fennie
authors: Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA.|Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA.
authors: Darrell G
authors: DG
authors: Schlom
authors: Department of Materials Science and Engineering and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors: Nasim
authors: N
authors: Alem
authors: Department of Materials Science and Engineering and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors: Venkatraman
authors: V
authors: Gopalan