[20a-PB8-1~9] 6.1 Ferroelectric thin films

[20a-PB8-6] Structural analyses and first-principles simulation
for new crystal symmetric BiFeO₃ grown on LaAlO₃ substrates

Hiroshi Naganuma^1,2, In-Tae Bae³, Andras Kovacs⁴, Hong Jian Zhao⁵, Jorge Iniguez⁵, 〇Shintaro Yasui⁶, Tomohiro Ichinose¹ (1.Tohoku Univ., 2.CNRS/Thales, 3.State Univ. NY, 4.ER-C Peter Grunberg Inst., 5.LIST, 6.Tokyo Tech.)

Keywords:Crystal structure, TEM

New crystal and electronic structures of BiFeO₃ film grown on LaAlO₃ substrate are comprehensively studied using advanced transmission electron microscopy (TEM) technique¹⁾ combined with first-principles theory. Cross-sectional TEM images reveal the BiFeO₃ film consists of two zones with different crystal structures. While zone II turns out to have rhombohedral BiFeO₃, the crystal structure of zone I matches none of BiFeO₃ phases reported experimentally or predicted theoretically. Detailed electron diffraction analysis combined with first-principles calculation allows us to determine that zone I displays a unique orthorhombic-like monoclinic new structure with space group of Cm (= 8). The growth mechanism and electronic structure in zone I are further discussed in comparison with those of zone II. This study ²⁾ is the first to provide an experimentally validated complete crystallographic detail of a highly strained BiFeO₃ that includes the lattice parameter as well as the basis atom locations in the unit cell.