Structural Phase Transitions to 2D and 3D Oxygen Vacancy Patterns in a Perovskite Film Induced by Electrical and Mechanical Nanoprobing

A reversible transition from a perovskite structure to a never ‐before‐seen oxygen‐vacancy‐ordered phase is imaged by scanning transmission electron microscopy in an epitaxial La2/3Sr1/3MnO3 −δ film during concurrent voltage pulsing and local mechanical straining. The new structure, comprising a regular 3D network of distorted oxygen polyhedra, forms when a piezo ‐controlled nanoprobe restricts the out‐of‐plane lattice expansion that migrating oxygen vacancies generate. AbstractOxygen vacancy migration and ordering in perovskite oxides enable manipulation of material properties through changes in the cation oxidation state and the crystal lattice. In thin ‐films, oxygen vacancies conventionally order into equally spaced planes. Here, it is shown that the planar 2D symmetry is broken if a mechanical nanoprobe restricts the chemical lattice expansion that the vacancies generate. Using in situ scanning transmission electron microscopy, a transition fr om a perovskite structure to a 3D vacancy‐ordered phase in an epitaxial La2/3Sr1/3MnO3 –δ film during voltage pulsing under local mechanical straining is imaged. The never ‐before‐seen ordering pattern consists of a complex network of distorted oxygen tetrahedra, pentahedra, and octahedra that, together, produce a corrugated atomic structure with lattice constants varying between 3.5 and 4.6 Å. The giant lattice distortions respond sensitively to strain variation s, offering prospects for non‐volatile...
Source: Small - Category: Nanotechnology Authors: Tags: Full Paper Source Type: research