Oxygen concentration and its effect on the leakage current in BiFeO3 thin films

Epitaxial c-axis oriented BiFeO3 (BFO) films were fabricated on (001) oriented SrTiO3 substrates by pulsed laser deposition. Nuclear resonance backscattering spectrometry was used to directly measure the oxygen concentration of as-deposited and annealed BFO films. Compared to the ideal stoichiometry of BFO, the as-deposited BFO film shows more than 10% oxygen deficiency. However, postannealing the as-deposited BFO films reduces the oxygen deficiency almost half. The reduced oxygen vacancies in annealed BFO films are believed to be responsible for the different leakage mechanisms and the two orders of magnitude drop in leakage current density.