Greg Stone1, Colin Ophus2, Turan Birol3, Jim Ciston2, Che-Hui Lee1, Ke Wang1, Craig Fennie3, Darrell Schlom3, Nasim Alem1, Venkat Gopalan1
1Penn State, 2Molecular Foundry, Lawrence Berkeley National Lab, 3Cornell University
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 An+1BnO3n+1 thin films by tuning layer dimension and strain. Using aberration-corrected scanning transmission electron microscopy with sub-Ångstrom resolution in Srn+1TinO3n+1 thin films, the IRG team demonstrated the coexistence of antiferroelectric, ferroelectric and new ordered and low-symmetry phases. The atomic rumpling of the rock salt layer, a critical feature in RP structures that is responsible for the competing phases, was directly imaged with exceptional quantitative agreement between electron microscopy and density functional theory down to 5pm (about 1/10th the size of a hydrogen atom). Such sub-atomic metrology can be transformative in bringing theory and experiments together for materials design at large.