Electron spin resonance investigation of oxygen-vacancy-related defects in BaTiO3 thin films

The Ti3+ center, based on a regular Ti site perturbed by an oxygen vacancy (VO), is identified by electron spin resonance (ESR) in textured BaTiO3 films. The center shows tetragonal symmetry along cubic ⟨100⟩ axes with g-factors: g‖=1.997, g⊥=1.904. The spectrum of this defect disappeared after the film annealing at 700°C in an O2 atmosphere. We describe the observed spectrum as Ti3+–VO couple defects or F+ center, which have never been observed in bulk BaTiO3. ESR is thus a unique tool to identify oxygen-vacancy-related defects, which have a large effect on the performance of ferroelectric films.