Oxygen Hole Character and Lateral Homogeneity in PrNiO2+δ Thin Films

Abstract

Using x-ray absorption spectroscopy with lateral resolution from the submillimeter to submicrometer range, we investigate the homogeneity, the chemical composition, and the nickel 3d- oxygen 2p charge transfer in topotactically reduced epitaxial PrNiO2+δ thin films. To this end, we use x-ray absorption spectroscopy in a standard experimental setup and in a soft x-ray microscope to probe the element and spatially resolved electronic structure modifications through changes of the nickel-2p and oxygen-1s absorption spectrum upon soft-chemistry reduction. We find that the reduction process is laterally homogeneous across a partially reduced PrNiO2+δ thin film sample for length scales down to 50 nm.

The Quest for High-Temperature Superconductivity in Nickelates under Ambient Pressure

“…Finally, in 2019, the group led by Harold Hwang at Stanford observed superconductivity with T c ≈ 8 K in Nd 0.8 Sr 0.2 NiO 2 [ 5 ]. With the focused effort of several groups, this result was improved further by optimizing the synthesis conditions [ 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. In La 0.8 Sr 0.2 NiO 2 , the best result reported was T c onset = 18.8 K and T c ( R = 0) = 16.5 K [ 13 ].…”