Growth of BiFeO3/SrTiO3 artificial superlattice structure by RF sputtering

Abstract

Asymmetric superlattice structures consisting of multiferroic BiFeO3 (BFO) and paraelectric SrTiO3 (STO) sublayers were grown on a Nb-doped STO substrate by RF magnetron sputtering at temperatures in the range 500-800 degrees C. For substrate temperatures less than 500 degrees C and at 800 degrees C, only poorly crystalline films resulted, whereas a BFO/STO superlattice structure film of great crystalline quality was obtained for a substrate temperature in the range 550-750 degrees C. The formation of a superlattice structure was confirmed through both the appearance of Bragg lines separated by Kiessig fringes in X-ray reflectivity curves and the satellite features of a (002) diffraction pattern. The clearly discernible main and satellite features on both sides of the substrate about the (002) STO Bragg peak of superlattice films indicate the high quality of the BFO/STO artificial superlattice structure. For BFO/STO superlattice films deposited at 600-700 degrees C, the increased crystalline quality with smaller interface roughness correlates with larger lattice strain and remanent polarization of the film. The lattice strain and interface quality might be important factors that influence the leakage and ferroelectric properties in BFO/STO artificial superlattices. (C) 2011 Elsevier B.V. All rights reserved.