Refractive index dispersion of swift heavy ion irradiated BFO thin films using Surface Plasmon Resonance technique

• Investigated the optical properties of BiFeO3 (BFO) thin films after irradiation using SPR.
• Otto configuration has been used to excite the surface plasmons using gold metal thin film.
• BFO thin films were prepared by sol–gel spin coating technique.
• Examined the refractive index dispersion of pristine and irradiated BFO thin film.

Swift heavy ion irradiation (SHI) is an effective technique to induce defects for possible modifications in the material properties. There is growing interest in studying the optical properties of multiferroic BiFeO3 (BFO) thin films for optoelectronic applications. In the present work, BFO thin films were prepared by sol–gel spin coating technique and were irradiated using the 15 UD Pelletron accelerator with 100 MeV Au9+ ions at a fluence of 1 × 1012 ions cm−2. The as-grown films became rough and porous on ion irradiation. Surface Plasmon Resonance (SPR) technique has been identified as a highly sensitive and powerful technique for studying the optical properties of a dielectric material. Optical properties of BFO thin films, before and after irradiation were studied using SPR technique in Otto configuration. Refractive index is found to be decreasing from 2.27 to 2.14 on ion irradiation at a wavelength of 633 nm. Refractive index dispersion of BFO thin film (from 405 nm to 633 nm) before and after ion radiation was examined.