Structural and Dielectric Properties of Sputter-Deposited Ba0.48Sr0.52TiO3/LaNiO3 Artificial Superlattice Films

Artificial superlattices consisting of dielectric Ba0.48Sr0.52TiO3 (BST) and conductive LaNiO3 (LNO) were fabricated on an Nb-doped SrTiO3(001) single-crystal substrate with radio-frequency magnetron sputtering at temperatures in the range of 500-700 degrees C. A symmetric structure with a sublayer thickness of 3 nm was deposited at varied substrate temperatures; the superlattices contained 10 periods of BST/LNO bilayers. The microstructure of these films was characterized with measurements of X-ray reflectivity and diffraction at high resolution. The formation of a superlattice structure was confirmed through the appearance of both the Bragg peaks separated by Kiessig fringes in X-ray reflectivity curves and the satellite peaks of a (002) diffraction pattern and the secondary-ion mass spectrometry profile. The clearly discernible main feature and satellite features observed in the (002) crystal truncation rod indicate the high quality of the BST/LNO artificial superlattice structure formed on a SrTiO3 substrate at all temperatures of deposition. The higher the temperature of deposition, the smaller the full width at half-maximum of the in-plane rocking curve and the better the crystalline quality. These BST/LNO artificial superlattices show a dielectric constant significantly enhanced relative to the BST single layers of the same effective thickness. Both the lattice strain and the interface quality affect the dielectric properties of the BST/LNO superlattices.