Spintronics with graphene-hexagonal boron nitride van der Waals heterostructures

Kamalakar, M. Venkata; Dankert, André; Bergsten, Johan; Ive, Tommy; Dash, Saroj P.

doi:10.1063/1.4902814

Cited by 46 publications

(43 citation statements)

References 35 publications

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“…3(c), it is clear that even after including the correction from the spin absorption due to the low-R c /R s contacts [24], the value of τ s is still lower than 400 ps for all three devices. We do not observe an increased τ s in our devices with two-layer-CVD-hBN encapsulating tunnel barriers, compared to the monolayer-CVD-hBN [18][19][20] encapsulating barriers. In contrast, in the case of an exfoliated-hBN encapsulating tunnel barrier, increasing the number of layers from monolayer to bilayer resulted in an increase of τ s due to large R c A contacts and enhanced screening of polymer contamination by bilayer-hBN [14][15][16][17].…”

Section: Discussionmentioning

confidence: 78%

“…Furthermore, previously reported spin-transport studies in graphene with CVD-hBN tunnel barriers incorporated a bare SiO 2 /Si substrate [18][19][20][21]. Even though hBN substrates have not been reported to enhance the spin-relaxation times of graphene compared to the SiO 2 /Si substrate [4], it can increase the mobility and thus the carrier diffusion.…”

Section: Introductionmentioning

confidence: 99%

“…Thicknesses of more than three layers are not suitable for * Author to whom all correspondence should be addressed: m.gurram@rug.nl spin injection [15,17,18] due to very high tunneling interface resistance. However, for large-scale spintronics applications, it is important to incorporate large-area chemical vapor deposition (CVD) grown hBN tunnel barriers in spin valves [18][19][20][21] and magnetic tunnel junctions [22,23]. Therefore, it is interesting to combine high-mobility graphene with the efficient CVD-hBN tunnel barriers for spintronics devices.…”

Section: Introductionmentioning

confidence: 99%

“…The potential of CVD-hBN as a tunnel barrier for electrical spin injection into graphene has been recently explored [18][19][20][21]. Electrical injection of spin current using a monolayer-CVD-hBN tunnel barrier is inefficient [18,19,21] due to its low contact resistance-area product R c A leading to the spin conductivity mismatch problem [24].…”

Section: Introductionmentioning

confidence: 99%

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

Gurram¹,

Omar²,

Zihlmann

et al. 2018

Phys. Rev. B

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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 SiO 2 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-CVDhBN 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.

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Section: Discussionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Gurram¹,

Omar²,

Zihlmann

et al. 2018

Phys. Rev. B

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“…The fit for the Hanle curve at zero gate voltage (solid red line in channel employing an h-BN tunnel barrier [19][20][21][22][23] . It is important to note that for van der Waals heterostructures, it is non-trivial to achieve clean interfaces 17,28 , and the impurities (or residues) at the interface can affect the electrical and spin related properties across the van der Waals heterostructures.…”

mentioning

confidence: 99%

Nanosecond spin relaxation times in single layer graphene spin valves with hexagonal boron nitride tunnel barriers

Singh

Katoch

et al. 2016

Applied Physics Letters

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Abstract:We present an experimental study of spin transport in single layer graphene using atomic sheets of hexagonal boron nitride (h-BN) as a tunnel barrier for spin injection. While h-BN is expected to be favorable for spin injection, previous experimental studies have been unable to achieve spin relaxation times in the nanosecond regime, suggesting potential problems originating from the contacts. Here, we investigate spin relaxation in graphene spin valves with h-BN barriers and observe room temperature spin lifetimes in excess of a nanosecond, which provides experimental confirmation that h-BN is indeed a good barrier material for spin injection into graphene. By carrying out measurements with different thicknesses of h-BN, we show that few layer h-BN is a better choice than monolayer for achieving high non-local spin signals and longer spin relaxation times in graphene.* Author to whom correspondence should be addressed: kawakami.15@osu.edu 2 Graphene is a promising spin channel material for next generation spintronic devices due to the experimental demonstration of long spin diffusion lengths at room temperature 1-3 and theoretical predictions of long spin relaxation times 4,5 arising from the weak spin-orbit and hyperfine couplings 5,6 .However, experimentally measured spin relaxation times [1][2][3]7,8 in graphene are orders of magnitude shorter than theoretically predicted 4,5 . In graphene spin valves, the tunnel barrier plays a crucial role for spin injection by circumventing the problem of impedance mismatch 9 between graphene and the ferromagnetic electrodes. As demonstrated by Han et. al. 8 , high quality tunnel barriers are critical for obtaining higher spin relaxation times (τ s ) in graphene because barriers with pinholes or rough surface morphology can cause additional contact-induced spin relaxation, which has received a great deal of interest recently. [10][11][12][13][14] As opposed to growing oxide tunnel barriers on graphene, a thin insulating twodimensional (2D) van der Waals material can also be used as a tunnel barrier. A particular material of interest is single (or few) layer h-BN because of its various suitable properties 15 : large energy band gap ~5.97 eV, high crystallinity, spin filtering 16 , absence of pinholes and dangling bonds, atomic lattice similar to graphene, and chemical stability at ambient conditions. In addition, atomically clean vertical heterostructures of h-BN/graphene can be mechanically assembled using polymer-based transfer techniques 17,18 . The first experimental report demonstrating spin injection into graphene using a monolayer h-BN tunnel barrier showed τ s less than 100 ps 19 . This was followed by the work of Kamalakar et. al. 20,21 and Fu et. al. 22 , which used chemically grown h-BN barriers, yielding τ s ~ 500 ps. Another recent study using an encapsulated geometry 23 with graphene sandwiched between a thick bottom layer of h-BN and a monolayer of h-BN on top showed τ s less than 200 ps. As evident from these studies, graphene spin valve devices ...

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Building Functional Memories and Logic Circuits with 2D Boron Nitride

Liu

Chen

Wang

et al. 2020

Adv Funct Materials

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The fast development of synthesis routes and preparation technology of 2D materials has motivated a rapid growth in the micro‐ and nanoelectronic memory devices, which gives rise to the breakthroughs in the semiconductor research area. Hexagon boron nitride (h‐BN) with excellent chemical, mechanical, and optical properties has been proven to have potential in overcoming the scaling limit to nanometer, and even sub‐nanometer lengths to replace the use of thick and stiff blocking dielectrics in two‐terminal or three‐terminal devices. The use of atomically thin h‐BN or h‐BN van der Waals heterostructures (vdWhs) can improve the reliability, capability, and functionality of memory devices. This is an encouraging strategy toward high‐density on‐chip integrated circuits, which has recently earned considerable interest. While the research in h‐BN material properties and characterization is comprehensively verified, specified mechanisms of resistive switching have not been analyzed in‐depth. Moreover, recent concern about novel structure design and expanding applications in electronics, optoelectronics, and spintronics has arisen. In this review, recent progress in h‐BN memories with volatile or nonvolatile properties is presented, expanding the memories to functional applications, and further challenges of the development of h‐BN‐based memories and logic circuits are discussed.

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Spintronics with graphene-hexagonal boron nitride van der Waals heterostructures

Cited by 46 publications

References 35 publications

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

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

Nanosecond spin relaxation times in single layer graphene spin valves with hexagonal boron nitride tunnel barriers

Building Functional Memories and Logic Circuits with 2D Boron Nitride

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