Highly dense and compositionally inhomogeneous nano-agglomerates in an epitaxial La0.8Sr0.2MnO3 thin film grown on (100)SrTiO3

Abstract

Microstructures in the thin film of La0.8Sr0.2MnO3 grown on (100) SrTiO3 by laser molecular beam epitaxy were characterized by transmission electron microscopy. Highly dense and dimensionally uniform nano-agglomerates were found embedded in thin film of La0.8Sr0.2MnO3. High-angle angular dark-field imaging, elemental mapping, and compositional analysis revealed that the nano-agglomerates are rich in manganese and poor in lanthanum. The ratio of Mn/La in the nano-agglomerates fluctuates. A salient feature of this compositional fluctuation within the nanoscale isthe formation of cubic MnO phase, which appears as the core of the nano-agglomerates.The La0.8Sr0.2MnO3 film is domain-oriented and two domains were identified on the basis of orthorhombic lattice. The orientation relationships between La0.8Sr0.2MnO3 domains and MnO were determined as [010]LSMO,1//[001]MnO and (100)LSMO,1//(110)MnO; [101]LSMO,2//[001]MnO and (010)LSMO,2//(100)MnO. The domain structuresand compositional inhomogeneities within nanoscale result in a textured microstructure, which is one of the most important parameters for tuning electronic properties in colossal magnetoresistance oxides.