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.
Highlights
Theoretically considered already decades ago [1], superconductivity in nickelates with infinite-layer structure was only realized recently [2]
spatially homogeneous oxidation state within the length scales probed in our experiment
we conclude that the oxygen deintercalation processes upon soft-chemistry reduction
Summary
Theoretically considered already decades ago [1], superconductivity in nickelates with infinite-layer structure was only realized recently [2]. Sr and Ca-doped rare-earth nickelate thin films with composition RNiO2 (R La, Pr, Nd) show a superconducting transition below 9–15 K [3,4,5,6]. This discovery triggered a lot of research activity that uncovered similarities [1, 7], and significant differences [8, 9] between nickelates and cuprates. These concern in particular the role of heteroepitaxy with the underlying substrate, the exact chemical composition and crystal structure as well as the homogeneity of the distribution of the dopant ions and the oxygen removal
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