Ferroelectric Srmno3 SrMnO3 Crystal Thin Film Grown on (110)-Oriented PMN-PT Substrate

Abstract

Exploring the growth of oxide perovskites on diverse substrates and their physical properties is fundamental for uncovering novel insights. Thin-film growth of single-crystal perovskite SrMnO3 (SMO) has been the focus of research owing to its emerging room-temperature multiferroicity. In this study, the epitaxial thin film of (110)-oriented SMO on the piezoelectric (110)-oriented (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) substrate, which has the largest converse piezoelectric effect, is grown for the first time. The effects of the thickness and oxygen annealing on the crystal structure, stoichiometry, and ferroelectric properties of the SMO film were systematically investigated. The tensile strain produced by the lattice mismatch between the bulk SMO and the PMN-PT substrate induces an expansion of the c-lattice parallel to the in-plane direction of the (110)-oriented thin film. The tetragonality (c/a) values determined using the X-ray reciprocal space maps of the 85- and 145-nm thick film were 1.011 and 1, respectively. The film shows a larger a-lattice parameter along both the in-plane and out-of-plane directions than the bulk material, resulting in volume expansion of the unit cell. The origin of this out-of-plane expansion was the production of oxygen vacancies owing to the reduced formation energy caused by the high elastic strain. Piezoelectric force microscopy revealed that the SMO film contained domains with strain-mediated in-plane and vacancy-mediated out-of-plane polarization. Furthermore, the piezoelectric response of the PMN-PT substrate efficiently modulated the biaxial tensile strain in the SMO film, which is a possible way to control the crystal structure of SMO and its ferroelectric properties.

Keywords: Strain-engineering, multiferroic materials, strain-induced ferroelectricity, defect chemistry, crystallographic orientation