Moiré superlattice in relatively rotated and stacked BiMnO3 nanoflakes

Abstract

Moiré superlattices through twistronics architecture in 2D van der Waals materials are rapidly progressing. Similar architecture can be extended to ionic systems to explore emerging functionalities. In this work, a moiré superlattice architecture is developed in BiMnO 3 nanoflakes. BiMnO 3 nanoflakes synthesised by the hydrothermal method. Their structure and morphology are confirmed through single-crystal electron diffraction (SAED) and diffraction contrast imaging (DCI). The as-synthesized sample is heat-treated to achieve a twist and stack architecture of superimposed nanoflakes. SAED, DCI, and high-resolution phase contrast imaging confirm the evidence of moiré superlattice formation in relatively rotated BiMnO 3 nanoflakes by a fixed angle of ~7° around the [010] stacking axis. Moiré superlattice consists of nanodomains that share (200) ms and (002) ms type distorted interfaces.Experimentally measured lattice parameter of the moiré superlattice is a ms ~4.44 nm, c ms ~4.36 nm. This can be well correlated with theoretically calculated lattice parameters. The strain distribution map of the moiré superlattice confirms the signature of a strain gradient.The arrangement of a locally distorted, relatively rotated group of orthorhombic and monoclinic orientational variants is shown. This study presents the first observation of the formation of a moiré superlattice in relatively rotated and superimposed BiMnO 3 nanoflakes. Such an architecture can be extended to perovskite and related oxide systems.