Dielectric enhancement in (0 0 1)-textured BaTiO3/LaNiO3 superlattice

Artificial superlattices consisting of ferroelectric BaTiO3 (BTO), and conductive LaNiO3 (LNO) layers were successfully prepared by rf magnetron sputtering with dual guns. The (0 0 1)-textured BTO and LNO layers were sequentially and coherently grown on (0 0 1)LNO/Pt/Ti/SiO2/Si substrates. The formation of superlattice structure was confirmed from the X-ray diffraction, cross-sectional image of transmission electron microscopy and depth profile of secondary ion mass spectrometer. An expansion of the c-axis of the BTO lattice was induced by the insertion of the LNO layers having a smaller lattice, and the expansion only slightly increases with the reduction of stacking periodicity of BTO layer below 12 nm. The formation of a conductive interdiffusion layer of 1.5–2.0 nm thick between the adjacent BTO and LNO layers was also found. A significant, but nearly the same extent, dielectric enhancement was achieved in the BTO/LNO superlattice with stacking periodicity of BTO ≤ 12 nm. The temperature dependence of dielectric constant also reveals the shift-up of Curie temperature in the strained BTO.