Abstract
Artificial superlattices having ferroelectric Ba0.48Sr0.52TiO3(BST) and conductive LaNiO3(LNO) as modulation length were grown epitaxially on Nb-doped SrTiO3 (001) substrates and LNO bottom-layer prepared by dual-gun Radio Frequency magnetron sputtering system. The formation of superlattice structure was confirmed from the x-ray reflectivity curves and SIMS depth profiles and (0 0 L) Bragg reflection of x-ray. A partial but nearly constant relaxation of in-plane strain in the superlattices was observed. From a macroscopic point of view, the strain in the superlattice structure contributes significantly to the dielectric enhancement. These BTO/LNO and BST/LNO artificial superlattices show a significant enhancement of dielectric constant relative to BTO and BST single layers of the same effective thickness. X-ray reflectivity measurement reveals that the superlattices have about the same interface roughness of BST/LNO. Consequently, nearly the same extent of dielectric enhancement results from the strained BST layer, along with a highly conductive interface zone in the superlattiecs.