Berlin 2024 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 52: Nickelates II

TT 52.3: Talk

Wednesday, March 20, 2024, 15:45–16:00, H 3010

influence of SrTiO₃ capping layer on infinite-layer nickelate thin films — •martando rath¹, yu chen¹, guillaume krieger², daniele preziosi², and marco salluzzo¹ — ¹CNR-SPIN, Napoli, Italy — ²Université, de Strasbourg, CNRS, IPCMS UMR, France

By using core-level x-ray photoemission spectroscopy (XPS), we studied the electronic properties of epitaxial NdNiO₂ thin films. In particular, we compare the surface-interface electronic structure of SrTiO₃ (STO)-capped and uncapped NdNiO₂ samples by core-level Nd 3d and Ni 2p XPS spectra. Our preliminary results show the enhancement of 3d⁹4f⁴L (L stands for a hole on the oxygen ligands) compared to 3d⁹4f³ peak in Nd 3d_5/2 of the nickelates sample capped with STO layer, which suggests the formation of a Nd(Ti,Ni)O₃ layer at the upper interface. The origin of this layer, recently found also at the bottom interface with the STO-single crystal, has been attributed to the polar discontinuity between neutral STO planes and charged NdNiO₂. A single Nd(Ti,Ni)O₃ layer indeed is able to solve the polar-catastrophe which would otherwise occur due to the alternating charged (NiO₂)³⁻ and Nd³⁺ layers. Furthermore, we find substantial differences of the Ni 2p spectra, which indicates the sample with capping layer preserves the Ni¹⁺ charge state with a fraction of Ni²⁺ in the final photo-excited state.

Keywords: X-ray photoelectron spectroscopy; Polar Interface; Electronic Structure; Infinite-layer Nickelates; Capping Layer