Dielectric properties of SrTiO3/LaNiO3 composite structure prepared by "sol-gel" method

In this work, Pt/SrTiO3(STO)/LaNiO3(LNO) and Pt/STO/Pt structures were fabricated on Si substrates using sol-gel method. Dielectric tunability characteristics of these two structures are investigated over temperature range of 300-80 K. As temperature decreases, relative dielectric constant and tunability of STO films in both structures increase linearly, while loss tangent (tan delta) decreases. STO prepared on LNO exhibits better crystallinity and dielectric tunability than that prepared on Pt. Furthermore, LNO top pole array with 0.2 mm diameter was prepared on STO/LNO using photosensitive sol-gel method, resulting in LNO/STO/LNO structure with symmetric electrode. Dielectric tunability tests reveal that, compared with Pt/STO/LNO structure, LNO/STO/LNO structure exhibits similar tunability, lower tan delta, higher figure-of-merit (FOM) values, and better tunability symmetry. Relative dielectric constant, tunability (350 kV/cm), and FOM are approximately 391, 60%, and 142.6 at 80 K, respectively. Further analysis shows that because of Schottky barrier at Pt/STO interface, the FOM and tunability symmetry of Pt/STO/LNO structure are worse than those of LNO/STO/LNO structure. These re-sults demonstrate that LNO electrode performs better than conventional inert metal electrodes.