Fan Zhen, Xiao Juanxiu, Liu Huajun, Yang Ping, Ke Qingqing, Ji Wei, Yao Kui, Ong Khuong P, Zeng Kaiyang, Wang John
Department of Materials Science and Engineering, National University of Singapore , 9 Engineering Drive 1, Singapore 117575, Singapore.
ACS Appl Mater Interfaces. 2015 Feb 4;7(4):2648-53. doi: 10.1021/am509016w. Epub 2015 Jan 21.
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.
具有高度拉长晶胞（c/a > 1.2）的铁电钙钛矿对于实现由显著的离子偏心位移诱导的巨极化特别有意义。在此我们表明，外延BiFe0.6Ga0.4O3（BFGO）薄膜呈现出具有孪晶畴的稳定类超四方结构，与薄膜厚度和衬底诱导应变无关，这通过高分辨率X射线衍射（HR-XRD）、透射电子显微镜（TEM）和压电力显微镜（PFM）得以证明。通过第一性原理计算研究了BFGO结构稳定性的起源。通过PFM、第一性原理计算和宏观极化-电场（P-E）滞后测量研究了BFGO的铁电性能。第一性原理计算揭示了约150 μC/cm(2)的巨铁电极化，并得到了实验证实。我们的研究提供了一条除广泛研究的应变工程之外采用Ga替代来稳定BiFeO3基外延薄膜中超四方结构的替代途径。
