Improvement of the Ferroelectric Properties of Chemically Synthesized Bi1/2Na1/2TiO3 Thin Films via Mn Doping

Lead-free ferroelectric (Bi0.5Na0.5)TiO3 (BNT) thin films were prepared on Pt/TiOx/SiO2/Si substrates via chemical solution deposition. Mn doping of these BNT films was very effective for improving the ferroelectric properties, and the doped Mn ion affected the leakage current properties in both low- and high-applied-field region. Specifically, the leakage current density was effectively reduced by doping with an appropriate amount of Mn. For example, a 1 mol% Mn-doped BNT thin film exhibited a well-shaped ferroelectric polarization–electric field hysteresis loop with a remanent polarization of 22 μC/cm2 and a coercive field of 165 kV/cm at room temperature. In addition, electron spin resonance and X-ray photoelectron spectroscopic analyses revealed that the Mn ions are doped into the Ti sites of BNT as Mn2+ or Mn3+.