Ferroelectric SrBi2Nb2O9 thin films by aqueous chemical solution deposition

Abstract

SrBi2Nb2O9 (SBN) thin films on a Pt/Ti/SiO2/Si substrate were prepared by aqueous chemical solution deposition. The precursor solution was synthesized by means of an 'aqueous solution-gel method', starting with stable, inexpensive and easily available inorganic salts which are dissolved in an aqueous solution of chelating or coordinating ligands (acetates and citrates). Afterwards the synthesized precursor was spin-coated. However, problems arose as a consequence of insufficient 'wetting' of the substrate surface by the aqueous solution (poor film-substrate adhesion). Instead of improving surface adhesion by the addition of a surface-wetting reagent, a new strategy was developed: prior to spin-coating the platinum surface characteristics were modified using a UV/ozone technique. In this way the precursor solution was not chemically changed. Wetting/wettability was verified by means of contact angle measurements. A uniform, three-layer thin film with a total thickness of about 200 nm was obtained after thermal treatment, as could be verified using SEM and XRD.