Strain Localization in Thin Films of Bi(Fe,Mn)O3 Due to the Formation of Stepped Mn4+-Rich Antiphase Boundaries

Abstract

The atomic structure and chemistry of thin films of Bi(Fe,Mn)O3 (BFMO) films with a target composition of Bi2FeMnO6 on SrTiO3 are studied using scanning transmission electron microscopy imaging and electron energy loss spectroscopy. It is shown that Mn4+-rich antiphase boundaries are locally nucleated right at the film substrate and then form stepped structures that are approximately pyramidal in three dimensions. These have the effect of confining the material below the pyramids in a highly strained state with an out-of-plane lattice parameter close to 4.1 Å. Outside the area enclosed by the antiphase boundaries, the out-of-plane lattice parameter is much closer to bulk values for BFMO. This suggests that to improve the crystallographic perfection of the films whilst retaining the strain state through as much of the film as possible, ways need to be found to prevent nucleation of the antiphase boundaries. Since the antiphase boundaries seem to form from the interaction of Mn with the Ti in the substrate, one route to perform this would be to grow a thin buffer layer of pure BiFeO3 on the SrTiO3 substrate to minimise any Mn-Ti interactions.

Giant Ferroelectric Polarization in Ultrathin Ferroelectrics via Boundary‐Condition Engineering

“…Another plausible explanation is that these atomic layers originate from an outward migration of the lower BiO planes due to the volatility of Bi. It should also be noted that similar structure with elongated lattice parameters occur in the form of antiphase boundary in doped BFO [28,29] , which suggests that these surface monolayers might be nucleation sites during growth. If more FeO 2 is added, this transient state would become proper BFO.…”

Study on Ca Segregation toward an Epitaxial Interface between Bismuth Ferrite and Strontium Titanate

“…Below this APB, the film is highly strained, while above it, it is relaxed and close to the bulk state. 25 Besides Nd nanorods formed through exsolution, 26,27 Ti-rich APBs are formed in Nd-and Ti-codoped BFO separating tetragonal distorted regions with strong polar ordering at each side of the defect. 28 Similar structures have been reported in other BFO-based systems.…”

Chemically Tunable Textured Interfacial Defects in PbZrO3-Based Antiferroelectric Perovskite Oxides

“…Perovskite oxides display abundant interfacial defects, e.g., domain walls and antiphase boundaries, due to their chemical and structural flexibility. − Benefitting from the advanced atom-resolved characterizations via transmission electron microscopy (TEM) or atomic force microscopy, it is found that the interfacial defects are not only simple structural boundaries separating adjacent regions with different crystal structures or crystallographic orientations but also act as functional entities for exploring emergent phenomena caused by local symmetry breaking. Notable examples include domain wall-localized free electron gas in ferroelectric BaTiO 3 , unusual electronic transport behavior and novel photovoltaic charge separation in multiferroic BiFeO 3 , − and ferroelectric dipole ordering in paraelectric CaTiO 3 . , Unlike fixed heterointerfaces, these homogeneous interfacial defects are more flexible, which can be controlled by external stimulants and/or chemical composition. − An antiphase boundary can be generated from the well-defined substrate steps in a La 2/3 Sr 1/3 MnO 3 thin film grown on Sr 2 RuO 4. Twin boundaries are produced by thermomechanical treatment on a BaTiO 3 /Pt film .…”