[20a-PB8-1~9] 6.1 強誘電体薄膜

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

永沼 博^1,2、Bae In-Tae³、Kovács András⁴、Zhao Hong Jian⁵、Íñiguez Jorge⁵、〇安井 伸太郎⁶、一ノ瀬 智浩¹ (1.東北大、2.CNRS/Thales、3.State Univ. NY、4.ER-C Peter Grünberg Inst.、5.LIST、6.東工大)

キーワード：結晶構造、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.