Characterization of Niobium-Doped Lead Titanate Thin Films

Lead titanate ( PbTiO3) thin films were deposited on silicon substrates covered with platinum by reactive sputtering using a single multicomponent-type target at high temperatures (around 500° C). Small chips of metallic niobium were incorporated into the target for doping purposes. Samples analyzed in this study were fabricated in such a way that the molar concentration of niobium was kept at 0, 1, 2, 3, or 4%. X-ray diffraction (XRD) patterns showed that samples doped with niobium tended to exhibit epitaxial growth on top of a (111)-oriented platinum electrode. At 2 mol% niobium doping, the tetragonality ratio (c/a) exhibited a maximum value and the dielectric permittivity showed a local minimum. The dielectric loss and leakage current characteristics of Nb-doped films were considerably improved. Electric displacement-electric field (D-E) hysteresis loops were observed at all doping concentrations. Some promising acoustic surface wave characteristics were also observed. Samples with 1 or 2 mol%Nb seem to be very promising candidates for integrated devices.