Effect of strain on the modifications in electronic structure and resistive switching in Ca-doped BiFeO3 films

Abstract

Strain-induced modifications in the structure, electronic structure, electrical, and ferroelectric properties of the Bi0.90Ca0.10FeO3 (BCFO)/Nb-doped SrTiO3 (100) films have been systematically studied in light of variation in film thickness. X-ray diffraction and ɸ-scan measurements confirm the single phase, (100) oriented epitaxial growth of all films. Room temperature absorption spectra show the presence of asymmetric broad peak around ∼2.5 eV, which is indicative of the presence of defect states inside the bandgap and is attributed to the oxygen vacancies. Improvement in the bipolar resistive switching behavior with a decrement in oxygen vacancies and improvement in ferroelectric properties with increasing film thickness suggest the crucial role of oxygen vacancies and strain in modifying the electrical properties of the BCFO films. Improvement in the ferroelectric behavior is attributed to the increment in the Fe 3d-O 2p hybridization, localization of Fe 3deg/Bi 6s-O 2p orbitals, and reduction in the oxygen vacancies with an increase in the film thickness. Observed stable retention and large ON/OFF switching ratio in BCFO films make them a promising candidate for application in the non-volatile memory device.