Ferroelectric properties of nb-doped Bi4Ti3O12 thin films prepared using surfactant in acid or basic atmosphere

Nb-doped Bi4Ti3O12 (BITN) thin films were prepared on Pt/Ti/SiO2/Si substrates by a sol-gel method. The remanent polarization (2P(r)) and coercive field (2(Ec)) values were 36 muC/cm(2) and 140 kV/cm, respectively. It was found that Nb doping can improve ferroelectric properties by reducing defects such as oxygen vacancies. The BITN thin films were also prepared by using surfactants in an acid or basic atmosphere, and their grain orientation and ferroelectric properties were investigated by X-ray diffraction, scanning electron microscopy and P-E hysteresis loop measurements. In particular, a completely c-axis-oriented BITN thin film was prepared by using a surfactant in a HCl atmosphere. The 2P(r) and 2E(c) values of the BITN thin film were 4 muC/cm(2) and 20 kV/cm, respectively, which were much lower than those of Bi4Ti3O12 (BIT) thin film with random orientation. A completely c-axis-oriented BITN thin film was grown and its ferroelectric properties were found to be similar to those of a BIT single crystal with c-axis orientation.