Stable Ferroelectric Perovskite Structure with Giant Axial Ratio and Polarization in Epitaxial BiFe0.6Ga0.4O3 Thin Films

• Published in: ACS applied materials & interfaces 2015-02, Vol.7 (4), p.2648-2653
• Main Authors: Fan, Zhen, Xiao, Juanxiu, Liu, Huajun, Yang, Ping, Ke, Qingqing, Ji, Wei, Yao, Kui, Ong, Khuong P, Zeng, Kaiyang, Wang, John
• Format: Article
• Language: English
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/am509016w

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/cm2 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.