Ferroelectric and Piezoelectric Properties of Polycrystalline BiFeO3 Thin Films Prepared by Pulsed Laser Deposition under Magnetic Field

Polycrystalline BiFeO 3 (BFO) thin films have been prepared on Pt/TiO 2 /SiO 2 /Si substrates by using a pulsed laser deposition (PLD) method under a magnetic field. The X-ray diffraction (XRD) pattern shows a single-phase perovskite structure with no secondary phases, and (010) and (020) peaks slightly shift to lower angles in comparison with those of a BFO thin film prepared without a magnetic field. A columnar structure and small grain size were observed and the leakage current is slightly high in comparison with that of a BFO thin film prepared without a magnetic field. A polarization versus electric field ($P$--$E$) hysteresis loop was obtained at RT and the polarization at zero electric field is 50 μC/cm 2 . Ferroelectric domain switching corresponding to up and down polarization states was confirmed. An enhanced piezoelectric coefficient ($d_{33}$) of about 100 pm/V has been obtained at a certain point. Ferroelectric and piezoelectric properties were affected by a columnar microstructure formed by magnetic field application.