Discovery of quantum confinement effect in sputtered topological insultor films and observation of room-temperature high spin–orbit torque

Invited

Abstract

In this talk, we will report and discuss the experimental demonstration and first-principles calcuation of quantum confinement in topological insulator. First, we report BixSe(1-x) films with high SOT at RT grown onto thermally oxidized silicon substrates by magnetron sputtering, which is a semiconductor industry compatible process. The dc planar Hall and ST-FMR methods were used for the characterization of SOT in BixSe(1-x)/CoFeB heterostructures with in-plane CoFeB. At RT, the of the sputtered BixSe(1-x) film is up to two orders of magnitude larger than that of HMs. Notably, we developed perpendicular CoFeB multilayers on BixSe(1-x) films, and we demonstrated switching of the magnetization using SOT arising from the BixSe(1-x) with very low switching current density in bilayers at RT. Second, we will report our discovery of the quantum confinement effect in topological insulators. The sputter deposited BixSe(1-x) has granular structure with grain size as small as approximately 6 nm. Electronic band-structure analysis indicates that the reduced dimensionality and quantum confinement strongly influences the spintronic properties of the TI. Our theory identifies the presence of lowly dispersive surface bands with large charge-to-spin conversion efficiency in nanoscale grains, which might explain the experimentally observed enhancement in the figure-of-merit. The demonstrated , ease of growth of the films on a silicon substrate, and successful growth and switching of perpendicular CoFeB multilayers on BixSe(1-x) film provide an avenue for the use of BixSe(1-x) as a spin-density generator in SOT-based memory and logic devices.

Mahendra DC, et al, "Room-temperature high spin–orbit torque due to quantum confinement in sputtered BixSe(1–x) films" Nature Materials. 17, 800-807 (2018); DOI: 10.1038/s41563-018-0136-z

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Presenters

  • Jianping Wang

    University of Minnesota, School of Physics and Astronomy, University of Minnesota, Electrical and Computer Engineering, University of Minnesota

Authors

  • Mahendra DC

    University of Minnesota, School of Physics and Astronomy, University of Minnesota

  • roberto grass

    University of Minnesota

  • Junyang Chen

    University of Minnesota

  • Mahdi Jamali

    University of Minnesota, Electrical and Computer Engineering, University of Minnesota

  • Danielle Hickey

    University of Minnesota

  • Delin zhang

    University of Minnesota

  • zhengyang zhao

    University of Minnesota

  • hongshi Li

    University of Minnesota

  • Patrick Quarterman

    National Institute of Standards and Technology, University of Minnesota

  • Yang Lv

    University of Minnesota, Electrical and Computer Engineering, University of Minnesota

  • mo li

    University of Minnesota

  • Aurelien Manchon

    King Abdullah University of Science and Technology

  • K. Andre Mkhoyan

    Chemical Engineering and Materials Science, University of Minnesota - Twin Cities, University of Minnesota, Chemical Engineering and Materials Science, University of Minnesota

  • Tony Low

    Electrical and Computer Engineering, University of Minnesota, University of Minnesota, Department of Electrical and Computer Engineering, University of Minnesota

  • Jianping Wang

    University of Minnesota, School of Physics and Astronomy, University of Minnesota, Electrical and Computer Engineering, University of Minnesota