Influence of seed layer on crystal orientation and electrical properties of (Na0.85K0.15)0.5Bi0.5TiO3 thin films prepared by a sol-gel process

Sol-gel derived lead-free (Na0.85K0.15)0.5Bi0.5TiO3 (NKBT) thin films, with and without a Pb0.8La0.1Ca0.1Ti0.975O3 (PLCT) seed layer, were fabricated on (111)Pt/Ti/SiO2/Si substrates. The influences of the seed layer on crystal orientation and electrical properties were investigated in detail. XRD indicated that the NKBT thin films fabricated with a seed layer were fully crystallized into a single perovskite structure, while the films fabricated under the same conditions, but without a seed layer, possessed a certain amount of pyrochlore phase. The NKBT film with a 14 nm-thick seed layer showed high (100) orientation, and exhibited enhanced electrical properties, such as a higher remanent polarization (Pr∼18 µC/cm2), a lower dielectric loss tangent (tan δ ∼0.023) and smaller transient current density (J<10−5 A/cm2).