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

摘要

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 Peudellosung fringes around the T-BFO (001) diffraction peak in X-ray diffraction theta-2 theta 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 M-A monoclinic to M-C 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 6.1V and a short-circuit current of -290 pA along the [100](T-BFO) direction. (C) 2016 The Japan Society of Applied Physics