Temperature dependent spin precession measurements in trilayer graphene utilizing co/graphene contacts

Abel, Joseph; Matsubayashi, Akitomo; Garramone, J. J.; LaBella, V. P.

doi:10.1116/1.4709768

Cited by 8 publications

(7 citation statements)

References 31 publications

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“…However, there is a huge sample-to-sample variation in the reported spin lifetimes which vary between tens of ps and several ns at room temperature. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] The predicted long intrinsic spin lifetimes of graphene are most likely masked by extrinsic sources of spin scattering and spin dephasing. [16][17][18] In particular, the direct contact of graphene to the underlying wafer and the electronic properties of the deposited spin injection and detection barriers are discussed as key factors that limit spin transport.…”

Section: Introductionmentioning

confidence: 99%

Suppression of contact-induced spin dephasing in graphene/MgO/Co spin-valve devices by successive oxygen treatments

et al. 2014

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By successive oxygen treatments of graphene non-local spin-valve devices we achieve a gradual increase of the contact resistance area products (RcA) of Co/MgO spin injection and detection electrodes and a transition from linear to non-linear characteristics in the respective differential dV -dI-curves. With this manipulation of the contacts both spin lifetime and amplitude of the spin signal can significantly be increased by a factor of seven in the same device. This demonstrates that contact-induced spin dephasing is the bottleneck for spin transport in graphene devices with small RcA values. With increasing RcA values, we furthermore observe the appearance of a second charge neutrality point (CNP) in gate dependent resistance measurements. Simultaneously, we observe a decrease of the gate voltage separation between the two CNPs. The strong enhancement of the spin transport properties as well as the changes in charge transport are explained by a gradual suppression of a Co/graphene interaction by improving the oxide barrier during oxygen treatment.

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Section: Introductionmentioning

confidence: 99%

Suppression of contact-induced spin dephasing in graphene/MgO/Co spin-valve devices by successive oxygen treatments

et al. 2014

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“…Spin lifetimes on the order of

μ

s have been proposed (). However, first experiments using non‐local graphene‐based spin valves on Si/SiO

_{2}

revealed typical spin lifetimes below 1 ns and electron mobilities below

10, 000 {normalcm}^{2} (Vs {false)}^{- 1}

. While the carrier mobilities could significantly be enhanced in suspended graphene devices or in devices in which the graphene sheet is in contact to hexagonal boron nitride (hBN), initial spin transport ex‐periments on those devices still exhibited short spin lifetimes .…”

Section: Introductionmentioning

confidence: 99%

Nanosecond spin lifetimes in bottom-up fabricated bilayer graphene spin-valves with atomic layer deposited Al2O3 spin injection and detection barriers

Drögeler

Volmer

Wolter

et al. 2015

Phys. Status Solidi B

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We present spin transport studies on bi‐ and trilayer graphene non‐local spin‐valves which have been fabricated by a bottom‐up fabrication method. By this technique, spin injection electrodes are first deposited onto Si++/SiO2 substrates with subsequent mechanical transfer of a graphene/hBN heterostructure. We showed previously that this technique allows for nanosecond spin lifetimes at room temperature combined with carrier mobilities which exceed 20,000thinmathspacenormalcm2(Vsfalse)−1. Despite strongly enhanced spin and charge transport properties, the MgO injection barriers in these devices exhibit conducting pinholes which still limit the measured spin lifetimes. We demonstrate that these pinholes can be partially diminished by an oxygen treatment of a trilayer graphene device which is seen by a strong increase of the contact resistance area products of the Co/MgO electrodes. At the same time, the spin lifetime increases from 1 to 2 ns. We believe that the pinholes partially result from the directional growth in molecular beam epitaxy. For a second set of devices, we therefore used atomic layer deposition of Al2O3 which offers the possibility to isotropically deposit more homogeneous barriers. While the contacts of the as‐fabricated bilayer graphene devices are non‐conductive, we can partially break the oxide barriers by voltage pulses. Thereafter, the devices also exhibit nanosecond spin lifetimes.

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“…[4,5] However, most electrical spin precession experiments measure spin lifetimes shorter than 1 ns and spin diffusion lengths smaller than 10 µm. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Therefore, there has been a strong effort to match spin lifetimes from theory to experimental values. Along this line, theoretical studies propose novel spin scattering mechanisms such as resonant spin scattering by magnetic impurities [24] or entanglement between spin and pseudospin by random spin orbit coupling, [25] which yield calculated spin lifetimes in the experimentally observed range.…”

mentioning

confidence: 99%

“…Long electron spin lifetimes as well as spin diffusion lengths are important prerequisites for enabling advanced spintronic devices. , Theoretically, graphene should fulfill these requirements thanks to its high charge carrier mobilities and its small spin orbit coupling . Accordingly, initial calculations predicted spin lifetimes of up to 1 μs for pristine graphene flakes. , However, for a long time the experimentally measured spin lifetimes at room temperature were shorter than 1 ns. − Such short lifetimes are normally also seen at low temperatures, − and only seldomly the 1 ns benchmark was reached at such low temperatures. , One explanation for this discrepancy between theoretically predicted and experimentally measured spin lifetimes is given by several recent studies, which demonstrated that the measured spin lifetimes are not intrinsic to graphene but are rather limited by invasive contacts. − Hence, much effort was put into the minimization of contact-induced effects and the optimization of the device fabrication. One way to diminish the effect of invasive contacts is the increase of the transport channel length .…”

mentioning

confidence: 99%

Spin Lifetimes Exceeding 12 ns in Graphene Nonlocal Spin Valve Devices

et al. 2016

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We show spin lifetimes of 12.6 ns and spin diffusion lengths as long as 30.5 µm in single layer graphene non-local spin transport devices at room temperature. This is accomplished by the fabrication of Co/MgO-electrodes on a Si/SiO2 substrate and the subsequent dry transfer of a graphenehBN-stack on top of this electrode structure where a large hBN flake is needed in order to diminish the ingress of solvents along the hBN-to-substrate interface. Interestingly, long spin lifetimes are observed despite the fact that both conductive scanning force microscopy and contact resistance measurements reveal the existence of conducting pinholes throughout the MgO spin injection/detection barriers. The observed enhancement of the spin lifetime in single layer graphene by a factor of 6 compared to previous devices exceeds current models of contact-induced spin relaxation which paves the way towards probing intrinsic spin properties of graphene.

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Temperature dependent spin precession measurements in trilayer graphene utilizing co/graphene contacts

Cited by 8 publications

References 31 publications

Suppression of contact-induced spin dephasing in graphene/MgO/Co spin-valve devices by successive oxygen treatments

Suppression of contact-induced spin dephasing in graphene/MgO/Co spin-valve devices by successive oxygen treatments

Nanosecond spin lifetimes in bottom-up fabricated bilayer graphene spin-valves with atomic layer deposited Al2O3 spin injection and detection barriers

Spin Lifetimes Exceeding 12 ns in Graphene Nonlocal Spin Valve Devices

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