title: Stable ferroelectric perovskite structure with giant axial ratio and polarization in epitaxial BiFe0.6Ga0.4O3 thin films.
abstract: Ferroelectric perovskites with strongly elongated unit cells (c/a > 1.2) are of particular interest for realizing giant polarization induced by significant ionic off-center displacements. Here we show that epitaxial BiFe0.6Ga0.4O3 (BFGO) thin films exhibit a stable super-tetragonal-like structure with twinning domains regardless of film thickness and substrate induced strain, evidenced with high resolution X-ray diffractometry (HR-XRD), transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM). The origin of the structural stability of BFGO is investigated by the first-principles calculation. The ferroelectric properties of BFGO are studied by PFM, first-principles calculation and macroscopic polarization-electric field (P-E) hysteresis measurement. A giant ferroelectric polarization of ∼150 μC/cm(2) is revealed by the first-principles calculations and confirmed by experiments. Our studies provide an alternative pathway of employing Ga-substitution other than the extensively studied strain engineering to stabilize the supertetragonal structure in BiFeO3-based epitaxial thin films.
authors.affiliation: Department of Materials Science and Engineering, National University of Singapore , 9 Engineering Drive 1, Singapore 117575, Singapore.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Fan
authors.forename: Juanxiu
authors.initials: J
authors.lastname: Xiao
authors.forename: Huajun
authors.initials: H
authors.lastname: Liu
authors.forename: Ping
authors.initials: P
authors.lastname: Yang
authors.forename: Qingqing
authors.initials: Q
authors.lastname: Ke
authors.forename: Wei
authors.initials: W
authors.lastname: Ji
authors.forename: Kui
authors.initials: K
authors.lastname: Yao
authors.forename: Khuong P
authors.initials: KP
authors.lastname: Ong
authors.forename: Kaiyang
authors.initials: K
authors.lastname: Zeng
authors.forename: John
authors.initials: J
authors.lastname: Wang
keywords: BiFeO3; epitaxial thin film; ferroelectric; giant polarization; supertetragonal