Modulated charged defects and conduction behaviour in doped BiFeO3 thin films

The charged defective structure in Bi1-xLaxFeO3 (BLF) and La-10% and Mg-2% co-doped BiFeO3 (BLFM) thin films as well as their relations to leakage and dielectric relaxation behaviour are investigated. Through temperature-dependent conductivity and x-ray photoelectron spectroscopy analyses, it is demonstrated that La doping suppresses but Mg doping increases the concentration of both oxygen vacancies (OVs) and Fe2+ ions. Correspondingly, the leakage mechanism evolves from grain boundary and space charge limited conduction of BLF (x = 0.2 and 0.1) to Poole-Frenkel emission of BLFM and BiFeO3. Although the dielectric relaxation originates from the migration of OVs, the formation of defect complexes between the acceptors and OVs is responsible for the increased activation energy of the BLFM film. (fast track communication)