Spin transport in two-layer-CVD-hBN/graphene/hBN heterostructures

M. Gurram*, S. Omar, S. Zihlmann, P. Makk, Q. C. Li, Y. F. Zhang, C. Schonenberger, B. J. van Wees

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

We study room-temperature spin transport in graphene devices encapsulated between a layer-by-layer-stacked two-layer-thick chemical vapor deposition (CVD) grown hexagonal boron nitride (hBN) tunnel barrier, and a few-layer-thick exfoliated-hBN substrate. We find mobilities and spin-relaxation times comparable to that of SiO2 substrate-based graphene devices, and we obtain a similar order of magnitude of spin relaxation rates for both the Elliott-Yafet and D'Yakonov-Perel' mechanisms. The behavior of ferromagnet/two-layer-CVDhBN/ graphene/hBN contacts ranges from transparent to tunneling due to inhomogeneities in the CVD-hBN barriers. Surprisingly, we find both positive and negative spin polarizations for high-resistance two-layer-CVD-hBN barrier contacts with respect to the low-resistance contacts. Furthermore, we find that the differential spininjection polarization of the high-resistance contacts can be modulated by dc bias from -0.3 to + 0.3 V with no change in its sign, while its magnitude increases at higher negative bias. These features point to the distinctive spin-injection nature of the two-layer-CVD-hBN compared to the bilayer-exfoliated-hBN tunnel barriers.

Original languageEnglish
Article number045411
Number of pages8
JournalPhysical Review. B: Condensed Matter and Materials Physics
Volume97
Issue number4
DOIs
Publication statusPublished - 9-Jan-2018

Keywords

  • HEXAGONAL BORON-NITRIDE
  • GRAPHENE
  • BILAYER
  • FILMS

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