SrBi₂Nb₂O₉ ferroelectric thin films deposited by pulsed laser deposition on textured and epitaxied platinum electrodes

Abstract
SBN thin films have been deposited by pulsed laser deposition on polycrystalline Pt/Ti/SiO₂/Si (Pt/Si) substrates and on Pt epitaxied on (100)MgO, (100) or (110)SrTiO₃ single crystals. On Pt/Si substrates, SBN polycrystalline film were obtained in situ at 700°C. X-ray diffraction (XRD) patterns indicate that these films exhibit some (001) preferential orientation and also reveal some formation of secondary phases which can be due to reaction between fîlm and substrate as suggested by Secondary Ions Mass Spectrometry (SIMS) results. Alternatively, in view of ferroelectric investigations, SBN films were deposited at lower temperature (typically 400°C) and then annealed at 750°C under air in order to allow better grain growth and to overcome this (001) preferential orientation that is deleterious for ferroelectric performances in such a structure. On single crystalline substrates, Pt bottom electrodes were deposited by d.c. sputtering at ~ 450° C. Their epitaxial growth was confirmed by Electron Channeling Pattern (ECP) and XRD in θ/2θ and φ-scan modes. SBN films grown on (l00)Pt/(l00)SrTiO₃ and (100)Pt(l00)MgO are (001) oriented and in-plane rotated by 45° with respect to the substrate while SBN films grown on (100)Pt/(110)SrTiO₃ are (116) oriented as shown by θ/2θ and --scans. SIMS also reveals interdiffusion. Finally, the morphologies of these various films (Scanning Electron Microscopy) have been compared.