Bottom electrode etching effect on the electrical properties of lead strontium titanate thin film

Abstract

(Pb_0.4Sr_0.6)TiO₃ thin films were prepared by a modified sol-gel method on Pt/Ti/SiO₂/Si substrates, where lower figure of merit of about 16% was observed in spite of higher tunability above 58%. The electrode surface was etched with different CF₄ and Ar gas ratios to modify the surface roughness. The electrical properties of PST thin films were investigated as a function of etching condition and film thickness. With changing CF₄/(Ar+CF₄) gas composition, the dielectric loss and the figure of merit were apparently affected which can be explained in terms of the surface roughness of Pt bottom electrode. When the Pt electrode surface was etched by using CF₄/(Ar+CF₄) = 20% gas mixture, the improvement above 25–27% in dielectric loss and figure of merit was observed, according to the decreased rms value of Pt surface of ∼30%, from 1.8 to 1.2 nm. The etching effect was found to be dominant for the dielectric loss and the thinner films.