Control of Polar Orientation and Lattice Strain in Epitaxial BaTiO3 Films on Silicon

Conventional strain engineering of epitaxial ferroelectric oxide thin films is based on the selection of substrates with suitable lattice parameter. Here we show that the variation of oxygen pressure during pulsed laser deposition is a flexible strain engineering method for epitaxial ferroelectric BaTiO3 films either on perovskite substrates or on Si(001) wafers. This unconventional growth strategy permits continuous tuning of strain up to high levels (ε>0.8%) in films of thickness exceeding of a hundred of nanometers, as well as selecting the polar axis orientation to be either parallel or perpendicular to the substrate surface plane.Financial support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2015-0496) and the MAT2017-85232-R (AEI/FEDER,UE), MAT2014-56063-C2-1-R, and MAT2015-73839-JIN projects, and from Generalitat de Catalunya (2014 SGR 734) is acknowledged. JL is financially supported by China Scholarship Council (CSC) with No. 201506080019. JL work has been done as a part of his Ph.D. program in Materials Science at Universitat Autònoma de Barcelona. J.G. acknowledges the RyC contract (RC-2012–11709). Electron microscopy observations at ORNL were supported by the U.S. Department of Energy (DOE), Basic Energy Sciences (BES), Materials Sciences and Engineering Division. Authors acknowledge the ICTS-CNME for offering access to their instruments and expertise. S.E. acknowledges the Spanish Ministry of Economy and Competitiveness for his PhD contract (SEV-2015-0496-16-3).Peer reviewe