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Charge Transfer and Defects in Ultrathin Metal Oxide – Graphene Spintronic Interfaces

POSTER

Abstract

The way metal oxides layers interface with graphene determines the performance of graphene spintronic devices. Titanium and Aluminum-based oxides are two widely used tunnel barriers in such devices at the contacts, and the impact of ultrathin metal oxide layers on graphene in electrical and spin transport properties and spin relaxation in graphene remains unclear. While it is believed that Al-oxide exhibits pinholes that lead to spin relaxation at contact interfaces, using Ti-based tunnel barriers, ns spin lifetimes are observed1,2.  In this work, we investigate the influence of TiOx and AlOx ultrathin layers on graphene via electrical measurement, structural and spectroscopic techniques,  and theory. We observe that both oxides layers lead to p-type doping in graphene, with atomic force microscopy revealing distinct coverage and topographic features. While surface charge transfer occurs in both cases, in sharp contrast to TiOx, the AlOx|graphene samples show the emergence of sp3 defects as revealed by Raman spectroscopy and confirmed by X-ray photoelectron spectroscopy. Our electronic structure calculations suggest interface configurations that match the charge transfer and defect emergence at these metal-oxide|graphene interfaces. This study concludes that while ultrathin TiOx on the top of graphene involves charge transfer doping, however, at the AlOx|Graphene interface, a combination of charge transfer and defect doping occurs that can explicate the implications to electrical and spin transport across such interfaces.  

Publication: (1) Tombros. Electronic Spin Transport and Spin Precession in Single Graphene Layers at Room Temperature. Nature 2007, 448 (7153), 571–574. https://doi.org/10.1038/nature06037.<br>(2) Panda. Ultimate Spin Currents in Commercial Chemical Vapor Deposited Graphene. ACS Nano 2020, 14 (10), 12771–12780. https://doi.org/10.1021/acsnano.0c03376.<br><br>

Presenters

  • Daria Belotcerkovtceva

    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden

Authors

  • Daria Belotcerkovtceva

    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden

  • Renan Marcel

    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden

  • Elin Berggren

    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden

  • R. R. Maddu

    Department of Materials Science and Engineering, Uppsala University, Box 35, SE-751 03 Uppsala, Sweden

  • Tapati Sarkar

    Department of Materials Science and Engineering, Uppsala University, Box 35, SE-751 03 Uppsala, Sweden

  • Yaroslav O Kvashnin

    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden, Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden

  • Andreas Lindblad

    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden

  • Olle Eriksson

    Uppsala University, Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden, Department of Physics and Astronomy, Uppsala University, Sweden, Department of Physics and Astronomy, Uppsala University and School of Science and Technology, Örebro University

  • M. Venkata Kamalakar

    Uppsala University, 1Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden