Self-organized, ordered array of coherent orthogonal column nanostructures in epitaxial La0.8Sr0.2MnO3 thin films

Abstract

We report direct transmission electron microscopy evidence of self-organized, ordered array of coherent orthogonal column nanostructures in epitaxial La0.8Sr0.2MnO3 (LSMO) thin films grown on (001) LaAlO3 (LAO) using pulsed-laser ablation. The orthogonal column nanostructures have an orthorhombic structure and are epitaxially grown on a continuous cubic perovskite LSMO thin-film layer that is epitaxially grown on (001) LAO substrate. The orthogonal column nanostructures exhibit a narrow size distribution, with the short edges having a length of about 25 nm and the long edge (growth direction) of ∼70 nm. The short edges are parallel to the [100] and [010] directions of LAO. All columns are encapsulated by uniformly thick amorphous-like grain boundaries and are “quasi” periodically arranged along the [100] and [010] directions of LAO. The continuous epitaxial layer of cubic perovskite structure grows along the [001] direction with an in-plane orientation relationship with respect to the substrate of 〈100〉LSMOC∥〈100〉LAO, while the orthorhombic column structures grow along its [11̄0] direction with an in-plane orientation relationship of [110]LSMOO∥[100]LAO and [001]LSMOO∥[010]LAO. The spontaneous formation of such self-organized, coherent column nanostructures can be considered to follow a type of Stranski–Krastanov growth mode without Oswald ripening.