Topotactic fluorination of perovskite strontium ruthenate thin films using polyvinylidene fluoride

Abstract

We investigated the polyvinylidene fluoride (PVDF)-mediated topotactic fluorination of two perovskite ruthenate thin films with different crystallographic structures, non-layered perovskite SrRuO₃ and layered perovskite Sr₂RuO₄. While the former ruthenate did not react with PVDF, the latter was fluorinated to form Sr₂RuO₃F₂ with a structure that exhibited a largely expanded c-axis. These results indicate that fluorine ions are preferentially inserted into the SrO rocksalt blocks in perovskite ruthenates, and that the oxygen atoms in the precursor oxide were partially removed upon fluorination. Finally, we noted that the Sr₂RuO₃F₂ film was insulating, with a resistivity of 4.1 × 10 Ω cm at 300 K. It should be noted that this resistivity is five orders of magnitude higher than that of the metallic Sr₂RuO₄ film (6.7 × 10⁻⁴ Ω cm).