Preparation and electrical properties of Nd and Mn co-doped Bi4Ti3O12 thin films

Ferroelectric thin films of Nd and Mn co-doped bismuth titanate, Bi3.15Nd0.85Ti3−xMnxO12 (BNTM) (x = 0–0.1), were fabricated on Pt/TiO2/SiO2/Si(100) substrates by a sol–gel technique. The BNTM films had a polycrystalline perovskite structure and uniform and dense surface morphologies. A lattice distortion was observed in the BNTM films due to Mn ion doping. The ferroelectric measurement of the films indicated that the values of coercive field (Ec) decreased gradually with the increase of the Mn content (x), however, the remanent polarization (Pr) increase firstly and then decrease with the increase of x. The sample with x = 0.05 had optimum electrical properties and a maximum 2Pr value. The 2Pr and 2Ec values of the film at a maximum applied electric field of 400 kV/cm were 38.3 μC/cm2 and 180 kV/cm, respectively. Moreover, this BNTM capacitors did not show fatigue behaviors after 1.0 × 1010 switching cycles at a frequency of 1 MHz, suggesting a fatigue-free character. The main reason for the increase of the 2Pr and the decrease of the 2Ec might be attributed to the lattice distortion in BNTM films due to Mn ion doping.