Influence of volatile element composition and Mn doping on the electrical properties of lead-free piezoelectric (Bi0.5Na0.5)TiO3 thin films

Lead-free piezoelectric (Bi0.5Na0.5)TiO3 (BNT) thin films were prepared by chemical-solution deposition. Perovskite single-phase BNT and Mn-doped BNT thin films were successfully fabricated at 600–700 °C on Pt/TiOx/SiO2/Si substrates. The BNT thin films fabricated from a stoichiometric BNT precursor solution showed considerable surface roughness and poor ferroelectric properties. The surface roughness of the films was improved by incorporating a controlled excess of volatile elements in the composition. In addition, the leakage current density of the BNT films, especially in the high-applied-field region, was reduced by doping with a small amount of Mn. Moreover, Mn doping markedly improved the ferroelectric properties of these films. Thus, 0.5 and 1.0 mol% Mn-doped BNT thin films exhibited well-shaped ferroelectric polarization (P)–electric field (E) hysteresis loops at room temperature. Furthermore, the synthesized BNT films showed a typical field-induced strain loop, and the effective d33 values were estimated at 41–60 and 39 pm/V for the BNT thin films with and without Mn doping, respectively.