title: Understanding Strain-Induced Phase Transformations in BiFeO3Thin Films.
abstract: Experiments demonstrate that under large epitaxial strain a coexisting striped phase emerges in BiFeO3thin films, which comprises a tetragonal-like (T') and an intermediateS' polymorph. It exhibits a relatively large piezoelectric response when switching between the coexisting phase and a uniformT' phase. This strain-induced phase transformation is investigated through a synergistic combination of first-principles theory and experiments. The results show that theS' phase is energetically very close to theT' phase, but is structurally similar to the bulk rhombohedral (R) phase. By fully characterizing the intermediateS' polymorph, it is demonstrated that the flat energy landscape resulting in the absence of an energy barrier between theT' andS' phases fosters the above-mentioned reversible phase transformation. This ability to readily transform between theS' andT' polymorphs, which have very different octahedral rotation patterns andc/aratios, is crucial to the enhanced piezoelectricity in strained BiFeO3films. Additionally, a blueshift in the band gap when moving fromRtoS' toT' is observed. These results emphasize the importance of strain engineering for tuning electromechanical responses or, creating unique energy harvesting photonic structures, in oxide thin film architectures.
authors.affiliation: Materials Science and Technology Division Oak Ridge National Lab Oak Ridge TN 37831 USA.
authors.forename: Hemant
authors.initials: H
authors.lastname: Dixit
authors.affiliation: Materials Science and Technology Division Oak Ridge National Lab Oak Ridge TN 37831 USA.
authors.forename: Christianne
authors.initials: C
authors.lastname: Beekman
authors.affiliation: Advanced Photon Source Argonne National Laboratory Argonne IL 60439 USA.
authors.forename: Christian M
authors.initials: CM
authors.lastname: Schlepütz
authors.affiliation: Materials Science and Technology Division Oak Ridge National Lab Oak Ridge TN 37831 USA.
authors.forename: Wolter
authors.initials: W
authors.lastname: Siemons
authors.affiliation: Department of Physics University of Michigan Ann Arbor MI 48109 USA.
authors.forename: Yongsoo
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Physics University of Michigan Ann Arbor MI 48109 USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: Senabulya
authors.affiliation: Department of Physics University of Michigan Ann Arbor MI 48109 USA.
authors.forename: Roy
authors.initials: R
authors.lastname: Clarke
authors.affiliation: Center for Nanophase Materials Sciences Oak Ridge National Lab Oak Ridge TN 37830 USA.
authors.forename: Miaofang
authors.initials: M
authors.lastname: Chi
authors.affiliation: Center for Nanophase Materials Sciences Oak Ridge National Lab Oak Ridge TN 37830 USA.
authors.forename: Hans M
authors.initials: HM
authors.lastname: Christen
authors.affiliation: Materials Science and Technology Division Oak Ridge National Lab Oak Ridge TN 37831 USA.
authors.forename: Valentino R
authors.initials: VR
authors.lastname: Cooper
keywords: multiferroic BiFeO3; phase coexistence; piezoelectric response; solid‐state nudged elastic band method