Interface and Surface Cation Stoichiometry Modified by Oxygen Vacancies in Epitaxial Manganite Films

Authors

  • Zhipeng Li,

    1. School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
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  • Michel Bosman,

    Corresponding author
    1. Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 3 Research Link, Singapore 117602, Singapore
    • Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 3 Research Link, Singapore 117602, Singapore
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  • Zhen Yang,

    1. School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
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  • Peng Ren,

    1. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
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  • Lan Wang,

    1. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
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  • Liang Cao,

    1. Physics Department, Faculty of Science, National University of Singapore, 2 Science Drive 3, 117551, Singapore
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  • Xiaojiang Yu,

    1. Physics Department, Faculty of Science, National University of Singapore, 2 Science Drive 3, 117551, Singapore
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  • Chang Ke,

    1. School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
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  • Mark B. H. Breese,

    1. Physics Department, Faculty of Science, National University of Singapore, 2 Science Drive 3, 117551, Singapore
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  • Andrivo Rusydi,

    1. Physics Department, Faculty of Science, National University of Singapore, 2 Science Drive 3, 117551, Singapore
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  • Weiguang Zhu,

    Corresponding author
    1. School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
    • School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore.
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  • Zhili Dong,

    Corresponding author
    1. School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
    • School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
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  • Yong Lim Foo

    Corresponding author
    1. Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 3 Research Link, Singapore 117602, Singapore
    • Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 3 Research Link, Singapore 117602, Singapore
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Abstract

Perovskite manganites are viewed as one of the key building blocks of oxide spintronics devices due to their attractive physical properties. However, cation off-stoichiometry at epitaxial interfaces between manganites and other materials can lead to interfacial dead layers, severely reducing the device performance. Here, transmission electron microscopy and synchrotron-based spectroscopy are used to demonstrate that oxygen vacancies during growth serve as a critical factor for modifying the cation stoichiometry in pulsed laser deposited La0.8Sr0.2MnO3 films. Near the film/substrate (SrTiO3) interface, A-site cations (La/Sr) are in excess when oxygen vacancies are induced during film growth, partially substituting Mn. Simultaneously, Sr cations migrate towards the film surface and form a SrO rock-salt monolayer. Consequentially, a gradient of the Mn nominal valence is observed along the film growth direction, leading to anomalous magnetic properties. The results narrow the selection range of useful oxygen pressures during deposition and demonstrate that accurate cation stoichiometry can only be achieved after oxygen vacancies are eliminated during growth. This finding suggests that the oxygen pressure serves as a tuning parameter for the interfacial dead layers and, hence, for control over device properties.

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