Spectroscopic and theoretical investigation of the electronic states of layered perovskite oxyfluoride Sr2RuO3F2 thin films

Abstract

We investigated the electronic structure of a layered perovskite oxyfluoride Sr 2 RuO 3 F 2 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 Sr 2 RuO 3 F 2 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 Sr 2 RuO 3 F 2 , predicting that Ru 4+ takes a high-spin configuration of (xy) ↑ (yz, zx) ↑↑ (3z 2-r 2) ↑ and that Sr 2 RuO 3 F 2 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 Sr 2 RuO 3 F 2 thin film, corresponding to the valence band and conduction band density of states, respectively, were drastically different compared to those of the Sr 2 RuO 4 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 crystal field.

Oxygen K-edge X-ray Absorption Spectra

“…This assignment is essentially reproduced in later experiments on Sr 2 RuO 4 and Ca 2 RuO 4 . ,− Fatuzzi et al performed an elegant experiment to distinguish the three 2p orbitals x , y , and z , from a combination of angular and polarization dependence. They performed a RIXS experiment on Sr 2 RuO 4 and Ca 2 RuO 4 and analyzed the low-energy excitations as a combination of the crystal field splitting of the t 2g states and the effect of the 4d spin–orbit coupling .…”

“…Chikamatsu et al compared the Sr 2 RuO 4 system with the oxyfluoride system Sr 2 RuO 3 F 2 . The oxygen K-edge spectra, in relation to other core and valence band spectroscopies, indicate that the Ru 4+ in Sr 2 RuO 3 F 2 is in a high-spin ground state, in contrast to the low-spin Sr 2 RuO 4 systems …”

“…The oxygen K-edge spectra, in relation to other core and valence band spectroscopies, indicate that the Ru 4+ in Sr 2 RuO 3 F 2 is in a high-spin ground state, in contrast to the low-spin Sr 2 RuO 4 systems. 431 Palladium Oxides. Palladium is an important catalyst, for which the reactivity is enhanced by fabricating nanosized metallic particles.…”

Strain-Induced Anion-Site Occupancy in Perovskite Oxyfluoride Films

“…For example, biaxial strains of ±3% are now routinely imposed in epitaxial oxide films that are tens of nanometers in thickness without loss of coherence with the substrate . The development of topochemical approaches − to convert perovskite oxide films to oxyfluorides has enabled the realization of numerous families of epitaxial oxyfluorides including ferrites, − manganites, , ruthenates, , chromates, cobaltites, and nickelates . The thin film nature of these samples has been exploited for functionality not accessible to bulk polycrystalline oxyfluorides, for instance, through reversible insertion and removal of F in NdNi­(O, F) 3−δ films and lateral patterning of SrFeO 2.5 /SrFeO 2 F heterostructures through spatially controlled topochemistry .…”