Effect of conductive oxide buffering on structural and nanoscale electrical properties of ultrathin SrTiO 3 films on Pt electrodes

Abstract

30 nm-thick SrTiO 3 (STO) dielectric thin films were grown on RuO 2 and LaNiO 3 (LNO)-buffered Pt/Ti/SiO 2/Si substrates at 500–700 °C. STO thin films that were grown on Pt and RuO 2 substrates are randomly oriented over a wide range of deposition temperatures. The use of an LNO buffer in the growth of STO film promotes the appearance of well developed (1 0 0)-crystallographic features. RuO 2 and LNO buffers effectively prevent the outdiffussion of Ti ions into the STO thin films at a high growth temperature. The Sr/Ti composition ratio of the STO films on RuO 2 and LNO at a high growth temperature is close to the stoichiometric value. However, an STO film grown on Pt without the buffer at a high temperature contains excess Ti because of the outdiffusion of Ti ions from the adhesive Ti layer. Both RuO 2 and LNO buffering enhances the dielectric constant of, and reduces the nanostructural leakage current in, STO films that were grown at a high growth temperature of 700 °C. Moreover, LNO has a similar crystalline structure and chemistry to STO film, and so substantially reduces the nanostructural leakage current of ultrathin STO films by effectively improving the film/electrode interface, the chemical homogeneity of the films, and the surface roughness of the films.