Influence of Oxygen to Argon Ratio on the Optical Band Gap of Bi3.25La0.75Fe1Ti2O12 Thin Films Deposited by RF Sputtering

Achieving wide band gap tunability in ferroelectric perovskite oxides is desirable for the development of photovoltaic device applications and solar cells. To tune the wide band gap of perovskite oxides, ferroelectric iron doped BLT thin films (BLFT) on SrTiO3 substrates were fabricated by RF sputtering with simple control of the oxygen content. The structural and optical properties were analyzed by X-ray diffraction, scanning electron microscopy and ultraviolet-visible absorption spectroscopy. As the oxygen content in the mixed Ar+O2 atmosphere was increased from 0% to 50%, the optical band gap of the thin films were decreased from 2.8 eV to 2.64 eV. The BLFT film deposited at an Ar/O2 ratio of 1/1 exhibited a significantly lower optical band gap than the other samples. This simple sputtering approach to controlling the band gap with a simple method can provide a new candidate tool for manipulating optoelectronics devices.