Spectroscopic and theoretical investigation of the electronic states of layered perovskite oxyfluoride S r2Ru O3 F2 thin films

We investigated the electronic structure of a layered perovskite oxyfluoride Sr2RuO3F2 thin film by hard x-ray photoemission spectroscopy (HAXPES) and soft x-ray absorption spectroscopy (XAS) as well as density functional theory (DFT)-based calculations. The core-level HAXPES spectra suggested that Sr2RuO3F2 is a Mott insulator. The DFT calculations described the total and site-projected density of states and the band dispersion for the optimized crystal structure of Sr2RuO3F2, predicting that Ru4+ takes a high-spin configuration of (xy)↑(yz,zx)↑↑(3z2-r2)↑ and that Sr2RuO3F2 has an indirect band gap of 0.7 eV with minima at the M,A and X,R points. HAXPES spectra near the Fermi level and the angular-dependent O 1s XAS spectra of the Sr2RuO3F2 thin film, corresponding to the valence band and conduction band density of states, respectively, were drastically different compared to those of the Sr2RuO4 film, suggesting that the changes in the electronic states were mainly driven by the substitution of an oxygen atom coordinated to Ru by fluorine and subsequent modification of the crystal field.