Atomic scale imaging of competing polar states in a Ruddlesden-Popper layered oxide

作者：Stone Greg; Ophus Colin; Birol Turan; Ciston Jim; Lee Che Hui; Wang Ke; Fennie Craig J; Schlom Darrell G; Alem Nasim; Gopalan Venkatraman^*

来源：Nature Communications, 2016, 7(1): 12572.

DOI：10.1038/ncomms12572

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), A(n+1)BnO(3n+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-Angstrom 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.

• 出版日期2016-8-31