Atomic-scale investigation of interface phenomena in two-dimensionally Sr-doped La2CuO4 and La2CuO4/ La2-xSrxNiO4 superlattices
Y. Wang, Y. E. Suyolcu, W. Sigle, U. Salzberger, F. Baiutti, G. Gregori, G. Cristiani, G. Logvenov, J. Maier, and P.A. van Aken
Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
Physics phenomena at interfaces of complex oxide heterostructures have stimulated intense research activity due to the occurrence of a broad range of electric and magnetic functionalities that do not pertain to the constituting single phases alone. Interface effects have been proven to be a powerful tool for improving or even inducing novel functionalities [1, 2]. In the case of interface superconductivity, the interatomic structure relaxation and charge transfer play a key role .
In this work, we combine atomic-resolved quantitative STEM imaging with analytical STEM-EELS/EDX analysis to investigate the interface effects in La2CuO4 (LCO)-based hetero-structures, i.e. superlattices of Sr two-dimensionally (2D) doped LCO, and LCO/La2-xSrxNiO4 (LSNO) hetero-structures, both exhibiting Tc up to 40 K, despite its non-superconducting constituents. HAADF images of the structure are displayed in Fig.1 confirming high-quality epitaxy. A detailed study of the cation distribution and concentration at the doped interfaces was performed by EDXS and EELS analyses. In the case of Sr-2D doped LCO superlattices, the analysis shows that Sr cations undergo an asymmetric redistribution, as a result of the MBE growth process. Oxygen K-edge fine structure analysis reveals that the hole concentration profile on the downward side of the nominal SrO layer is clearly decoupled from the Sr-profile indicating an accumulation of positive charges compensating the negatively charged SrO planes (Fig.2).
These results were supplemented by quantitative analysis of atomic-resolved high-angle annular dark-field (HAADF) and annular bright-field (ABF) images, which were simultaneously acquired. From these images the local lattice and copper-apical-oxygen distortions at the interfaces were evaluated. The relation of these results with the observed Tc will be discussed.
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 Y.Wang et al., ACS Appl. Mater. Interfaces (2016) DOI :10.1021/acsami.5b12813
 The research leading to these results has received funding from the European Union Seventh Framework Program under Grant Agreement 312483-ESTEEM2 (Integrated Infrastructure Initiative I3).
To cite this abstract:Yi Wang, Y. Eren Suyolcu, Wilfried Sigle, Ute Salzberger, Federico Baiutti, Giuliano Gregori, Georg Cristiani, Gennady Logvenov, Joachim Maier, Peter van Aken; Atomic-scale investigation of interface phenomena in two-dimensionally Sr-doped La2CuO4 and La2CuO4/ La2-xSrxNiO4 superlattices. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/atomic-scale-investigation-of-interface-phenomena-in-two-dimensionally-sr-doped-la2cuo4-and-la2cuo4-la2-xsrxnio4-superlattices/. Accessed: December 5, 2022
EMC Abstracts - https://emc-proceedings.com/abstract/atomic-scale-investigation-of-interface-phenomena-in-two-dimensionally-sr-doped-la2cuo4-and-la2cuo4-la2-xsrxnio4-superlattices/