On the novel biaxial strain relaxation mechanism in epitaxial composition graded La 1-x Sr x MnO 3 thin film synthesized by RF magnetron sputtering

Abstract

We report on a novel method to fabricate composition gradient, epitaxial La 1-x Sr x MnO 3 thin films with the objective to alleviate biaxial film strain. In this work, epitaxial, composition gradient La 1-x Sr x MnO 3 , and pure LaMnO 3 and La 0.67 Sr 0.33 MnO 3 thin films were deposited by radio frequency (RF) magnetron sputtering. The crystalline and epitaxy of all films were first studied by symmetric θ-2θ X-ray diffraction (XRD) and low angle XRD experiments. Detailed microstructural characterization across the film thickness was conducted by high-resolution transmission electron microscopy and electron diffraction. Four compositional gradient domains were observed in the La 1-x Sr x MnO 3 film ranging from LaMnO 3 rich to La 0.67 Sr 0.33 MnO 3 at the surface. A continuous reduction in the lattice parameter was observed accompanied by a significant reduction in the out-of-plane strain in the film. Fabrication of the composition gradient La 1-x Sr x MnO 3 thin film was found to be a powerful method to relieve biaxial strain under critical thickness. Besides, the coexistence of domains with a composition variance is opening up various new possibilities of designing new nanoscale structures with unusual cross coupled properties.