Effects of Donor Ion Doping on the Orientation and Ferroelectric Properties of Bismuth Titanate Thin Films

Abstract

Bismuth layer-structured ferroelectric thin films, Bi4Ti3O12 (BTO) and donor (V5+, W6+, and Nb5+)-doped BTO (BTV, BTW, and BTN) were prepared on Pt(111)/Ti/SiO2/Si(100) substrates by a sol–gel method. We investigated the doping effects of donor ions on the grain orientation and the electrical properties. Donor ions which substituted for Ti4+ ions in pseudoperovskite layers of BTO decreased the c-axis orientation and increased the remanent polarization (2Pr). The fatigue resistances of donor-doped thin films were shown to be superior to that of BTO, and the leakage currents were decreased by approximately 1 order of magnitude compared with BTO. The improvements of electrical properties with donor doping in BTO could be attributed to the changes in grain orientation and space charge density in the thin films.