Dielectric and optical properties of BiFeO3–(Na0.5Bi0.5)TiO3 thin films deposited on Si substrate using LaNiO3 as buffer layer for photovoltaic devices

Abstract: Highly (100)-oriented BiFeO3–(Na0.5Bi0.5)TiO3 thin films without undesirable phases were synthesized by chemical solution deposition. The preparation of BiFeO3–(Na0.5Bi0.5)TiO3 sol and deposition procedure were studied. BiFeO3–(Na0.5Bi0.5)TiO3 thin films were deposited onto SiO2/Si substrates via a sol–gel method, with LaNiO3 as buffer layer. X-ray diffraction analyses show that the BiFeO3–(Na0.5Bi0.5)TiO3 films are highly (100)-oriented due to lattice match growth. Smooth surface with evenly distributed grains as small as about 50nm were observed by scanning electron microscope. The dielectric and insulating characteristics against applied field, and optical properties were studied. It is found that the introduction of Ti4+ reduces the number of oxygen vacancy greatly and thus can suppress the leaking current. The film has a conspicuous absorption in the blue and green light region, and band gap of about 2.74eV. [Copyright &y& Elsevier]