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Title: Electronic spin transport in dual-gated bilayer graphene
Authors: Avsar, A 
Vera-Marun, I.J
Tan, J.Y 
Koon, G.K.W 
Watanabe, K
Taniguchi, T
Adam, S 
Keywords: Carrier concentration
Magnetic devices
Magnetic resonance
Reconfigurable hardware
Relaxation time
Semiconductor junctions
Charge mobilities
Charge neutrality
Comparative studies
Density dependence
Impedance mismatch
Low temperatures
Spin relaxation time
Spin-valve devices
Issue Date: 2016
Citation: Avsar, A, Vera-Marun, I.J, Tan, J.Y, Koon, G.K.W, Watanabe, K, Taniguchi, T, Adam, S, Ozyilmaz,Barbaros (2016). Electronic spin transport in dual-gated bilayer graphene. NPG Asia Materials 8 (6) : e274. ScholarBank@NUS Repository.
Abstract: The elimination of extrinsic sources of spin relaxation is key to realizing the exceptional intrinsic spin transport performance of graphene. Toward this, we study charge and spin transport in bilayer graphene-based spin valve devices fabricated in a new device architecture that allows us to make a comparative study by separately investigating the roles of the substrate and polymer residues on spin relaxation. First, the comparison between spin valves fabricated on SiO2 and BN substrates suggests that substrate-related charged impurities, phonons and roughness do not limit the spin transport in current devices. Next, the observation of a fivefold enhancement in the spin-relaxation time of the encapsulated device highlights the significance of polymer residues on spin relaxation. We observe a spin-relaxation length of ?10 ?m in the encapsulated bilayer, with a charge mobility of 24 000 cm2Vs-1. The carrier density dependence on the spin-relaxation time has two distinct regimes; n<4 × 1012 cm-2, where the spin-relaxation time decreases monotonically as the carrier concentration increases, and n ? 4 × 1012 cm-2, where the spin-relaxation time exhibits a sudden increase. The sudden increase in the spin-relaxation time with no corresponding signature in the charge transport suggests the presence of a magnetic resonance close to the charge neutrality point. We also demonstrate, for the first time, spin transport across bipolar p-n junctions in our dual-gated device architecture that fully integrates a sequence of encapsulated regions in its design. At low temperatures, strong suppression of the spin signal was observed while a transport gap was induced, which is interpreted as a novel manifestation of the impedance mismatch within the spin channel.
Source Title: NPG Asia Materials
ISSN: 18844049
DOI: 10.1038/am.2016.65
Appears in Collections:Staff Publications

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