Structural and Electrical Properties of BiFeO<sub>3</sub> Fabricated on <i>C</i>-Sapphire Substrates Using a Double SrTiO<sub>3</sub>/TiO<sub>2</sub> Buffer Layer

Abstract

BiFeO3 (BFO) thin films were deposited by pulsed laser deposition (PLD) on c-plane sapphire substrates with a double SrTiO3/TiO2 oxide buffer layer grown by laser molecular beam epitaxy (laser-MBE). X-ray diffraction data showed the highly (111)-oriented perovskite phase in the BFO films with SrTiO3/TiO2 buffer layers, compared to the polycrystalline thin film grown directly on sapphire substrates. The epitaxial BiFeO3 thin films inherit its orientation from the underlying SrTiO3 buffer layer and have two in-plane orientations: (111)[1-10] BiFeO3 // (0001)[1-100] Al2O3 plus a twin variant related by a 180° in-plane rotation. The BiFeO3 thin films with the buffer layer show an out-of-plane remanent polarization of 81.5μC/cm2, which is comparable to the remanent polarization of BiFeO3 prepared on other single crystal substrates. Electrical measurements demonstrate that the BiFeO3 thin films with the buffer layer exhibit excellent fatigue endurance and a low leakage current density relative to the films without the buffer layer. These results indicate that the (111)-oriented BiFeO3 films with favorable electrical performance could be epitaxially grown on sapphire substrates using the double SrTiO3/TiO2 buffer layer.