Orientation dependence of ferroelectric behavior of BiFeO3 thin films

Multiferroic BiFeO3 (BFO) thin films with (111), (100), (110) preferred, and random orientations were deposited by radio frequency magnetron sputtering on SrRuO3-buffered SrTiO3(111), SrTiO3(100), SrTiO3(110), and Pt(111)/Ti/SiO2/Si(100) substrates, respectively. The orientation dependences of ferroelectric and fatigue behavior of the BFO thin films were investigated. As expected, the (111)-oriented BFO thin film exhibits the highest, giant ferroelectric polarization (2Pr=196.9 μC/cm2) at 1 kHz and room temperature using positive up negative down measurement, while the (100)-oriented BFO thin film possesses an almost fatigue-free behavior up to 5.25×107 switching cycles when measured at 100 kHz and room temperature. The observed behavior confirms that the largest spontaneous polarization direction and the fatigue endurance are (111) and (100) for BFO thin films, respectively. Regardless of the film orientation, the charge carriers that are responsible for dielectric relaxation and conductivity are oxygen vacancies (VO••) .