Fabrication and characterization of Bi-substituted yttrium iron garnet films by pulsed laser deposition

Abstract

We have systematically investigated the effects of processing parameters, including various oxygen pressures (Po₂) ranging from 200 to 1000 m Torr and substrate temperatures (T_s) ranging from 500 to 750°C, on the characteristics of Bi-substituted yttrium iron garnet (Bi:YIG) films grown on (111) gadolinium gallium gamet (GGG) substrates. Bi: YIG films were grown using a pulsed laser deposition method with an ArF excimer laser (λ=193 nm). Although the compositions of all the Bi:YIG films grown at the constant T_s of 600°C were close to the target composition irrespective of Po₂, the Bi contents were slightly increased with increasing Po₂, which was consistent with the variation in Faraday rotation angles (θ_F). In addition, the crystallinity of the Bi:YIG films was deteriorated with increasing Po₂, and their grains became irregular. At T_s above 700°C, Bi-deficient yttrium iron garnet films were grown. Consequently, high quality epitaxial Bi:YIG films exhibiting Faraday rotation angles of −1.0≈−1.5 degree/μm were successfully grown at the substrate temperatures in the range of 500–650°C when the Po₂ of 200 mTorr was used.