Evaluation of strain-dependent dielectric properties in BaTiO3/LaNiO3 and (Ba, Sr) TiO3/LaNiO3 artificial superlattice films on LaNiO3-coated SrTiO3 substrates

We formed strained artificial superlattices of BaTiO3/LaNiO3(BTO/LNO) and (Ba0.48Sr0.52)TiO3/LaNiO3(BST/LNO) on LaNiO3-coated SrTiO3 (001) substrates by dual-gun radio-frequency magnetron sputtering. The (00L) crystal truncation rod intensity profiles confirm the formation of a superlattice structure. The BTO (or BST) sublayer in the artificial superlattice is under biaxial compressive stress whereas the LNO sublayer is under biaxial tensile stress. Both BTO/LNO and BST/LNO superlattices of total thickness similar to 60 nm exhibit some degree of strain relaxation, even though the modulation length is less than the critical value to generate misfit dislocations. These BTO/LNO and BST/LNO artificial superlattices show a dielectric constant significantly enhanced relative to BTO and BST single layers of the same effective thickness. From a macroscopic point of view, the strain in the superlattice structure contributes significantly to the dielectric enhancement. (c) 2005 The Electrochemical Society.