Influence of fluorination on electronic states and electron transport properties of Sr2IrO4 thin films

Abstract

We fabricated layered-perovskite Sr₂IrO_4−xF_2x thin films by combining pulsed-laser deposition with topotactic fluorination and investigated their structures, electronic states, and electron transport properties. In the fluorination process, the insertion of fluorine into SrO rock-salt layers and the partial removal of oxygen occurred simultaneously while keeping Ir⁴⁺. The fluorine amount was evaluated to be 2x ≈ 3, which was much larger than the bulk value. Optical and photoemission measurements revealed that the effective total angular momentum J_eff = 3/2 is stabilized upon fluorination owing to the large electronegativity of fluorine. The Sr₂IrO_4−xF_2x film exhibited a semiconducting behavior described by Efros–Shklovskii variable-range hopping with ρ(T) ≈ T^−1/2. These results will be useful for modifying electronic states by anion doping to explore unprecedented physical properties in Ruddlesden–Popper-type iridates.