Effects of LaNiO₃ Conductive Buffer Layer on The Structural and Electrical Characteristics of Ba_0.4Sr_0.6TiO₃ Thin Films Prepared by RF Magnetron Sputtering

Abstract

Sputter-deposited LaNiO 3 (LNO) was used as a conductive buffer layer for the deposition of 80-nm-thick Ba 0.4 Sr 0.6 TiO 3 (BST) thin films on Pt/Ti/SiO 2 /Si substrates by rf magnetron sputtering. Smooth and highly (100)-oriented perovskite films of BST were grown on the (100)-textured LNO by deposition at temperatures ≧200 °C. However, a relatively rough and weakly crystallized BST film was obtained by deposition directly on Pt/Ti/SiO 2 /Si substrates at 500 °C. Satisfactory dielectric constants of 160 to 320 were achieved for films deposited on LNO at temperatures from 350 to 550 °C, while a low dielectric constant of 120 was obtained for the film deposited on Pt at 500 °C. All the films in a Pt/BST/LNO or Pt/BST/Pt capacitor configuration basically showed a similar ohmic conduction characteristic of low conductivity in low bias regime up to a transition voltage around 1–3 V, and beyond that a nonohmic conduction with current rapidly increasing against the applied bias occurred. However, the films deposited on LNO would have a more moderate nonohmic conduction than that of the film deposited on Pt.