Migration kinetics of oxygen vacancies in Mn-modified BiFeO3 thin films

Abstract

Migration kinetics of oxygen vacancies in BiFe0.95Mn 0.05O3 thin film were investigated by the temperature -dependent leakage current as well as the electric field and temperature-dependent impedance spectroscopy. The BiFe0.95Mn 0.05O3 is of an abnormal leakage behavior, and an Ohmic conduction is observed regardless of varied temperatures and electric fields. The temperature-dependent impedance spectroscopy under different resistance states is used to illuminate different leakage behavior between BiFe 0.95Mn0.05O3 and pure BiFeO3. The impedance spectroscopy under a high resistance state shows that the first ionization of oxygen vacancies is responsible for the dielectric relaxation and electrical conduction of BiFe0.95Mn0.05O3 in the whole temperature range of 294 to 474 K; the BiFeO3 exhibits similar dielectric relaxation and electrical conduction behavior in the low-temperature range of 294-374 K, whereas the short-range motion of oxygen vacancies was involved in the high-temperature range of 374-474 K. The impedance spectroscopy under a low resistance state demonstrates that the dielectric relaxation and conduction mechanisms almost keep unchanged for BiFe 0.95Mn0.05O3, whereas the hopping electrons of Fe2+-VO-Fe3+ and Fe2+-Fe 3+ are responsible for its dielectric relaxation and conduction mechanism of BiFeO3. Different impedance spectroscopy under low and high resistance states confirms that an abnormal leakage behavior of BiFe 0.95Mn0.05O3 is related to different migration kinetics of oxygen vacancies, obviously differing from that of BiFeO 3. © 2011 American Chemical Society.