Strain evolution of epitaxial tetragonal-like BiFeO3 thin films on LaAlO3(001) substrates prepared by sputtering and their bulk photovoltaic effect

Abstract

The structural evolution of high-quality 3.3–73.2-nm-thick tetragonal-like BiFeO3 (T-BFO) thin films grown on LaAlO3(001) substrates and the bulk photovoltaic effect of the films were investigated. The T-BFO films were grown by rf magnetron sputtering, showing the Peudellösung fringes around the T-BFO (001) diffraction peak in X-ray diffraction θ–2θ patterns. These indicate the structural coherence between the surface and the interface in the surface normal direction of the films. High-resolution synchrotron X-ray diffraction analysis and transmission electron microscopy reveal that the lattice relaxation behavior from the MA monoclinic to MC monoclinic structure occurs as the film thickness increases. The domain structure was partly controlled by using a vicinal LAO (001) substrate along [100]. Regarding the current–voltage characteristics of the Pt/T-BFO/Pt coplanar capacitor under violet laser illumination, T-BFO films show an anomalous photovoltaic effect with an open-circuit voltage of 6.1 V and a short-circuit current of −290 pA along the [100]T-BFO direction.