Micrometer-Scale Ballistic Transport in Encapsulated Graphene at Room Temperature

Mayorov, Alexander S.; Gorbachev, Roman; Морозов, С. В.; Britnell, L.; Jalil, R.; Пономаренко, Л. А.; Blake, P.; Новоселов, К. С.; Watanabe, Kenji; Taniguchi, Takashi; Geǐm, A. K.

doi:10.1021/nl200758b

Cited by 1,517 publications

(1,241 citation statements)

References 18 publications

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“…This mobility degradation is likely due to the presence of a small number of bubbles and wrinkles, as observed in the atomic force microscopy images of Supplementary Fig. S3, which can introduce charge inhomogeneity 26 . However, as hysteresis is not observed in all the GB devices, it is obvious that the existence of underlying MoS 2 layer gives rise to the hysteresis in transfer curve of the GBM devices.…”

Section: Resultsmentioning

confidence: 98%

Controlled charge trapping by molybdenum disulphide and graphene in ultrathin heterostructured memory devices

et al. 2013

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Atomically thin two-dimensional materials have emerged as promising candidates for flexible and transparent electronic applications. Here we show non-volatile memory devices, based on field-effect transistors with large hysteresis, consisting entirely of stacked two-dimensional materials. Graphene and molybdenum disulphide were employed as both channel and charge-trapping layers, whereas hexagonal boron nitride was used as a tunnel barrier. In these ultrathin heterostructured memory devices, the atomically thin molybdenum disulphide or graphene-trapping layer stores charge tunnelled through hexagonal boron nitride, serving as a floating gate to control the charge transport in the graphene or molybdenum disulphide channel. By varying the thicknesses of two-dimensional materials and modifying the stacking order, the hysteresis and conductance polarity of the field-effect transistor can be controlled. These devices show high mobility, high on/off current ratio, large memory window and stable retention, providing a promising route towards flexible and transparent memory devices utilizing atomically thin two-dimensional materials.

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Section: Resultsmentioning

confidence: 98%

Controlled charge trapping by molybdenum disulphide and graphene in ultrathin heterostructured memory devices

et al. 2013

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“…8,17 For charge transport, it has been shown that the carrier mobility of graphene devices on SiO 2 is mainly limited by interfacial charged impurities, surface roughness, and phonons. [18][19][20] The demonstration of an order-of-magnitude improvement in the mobility of graphene encapsulated between atomically flat, charge trap free boron nitride crystals 21,22 has triggered the recent spin transport studies in encapsulated single layer and recently bilayer graphene-based spin valves, where a spin-relaxation length of up to~12 μm and~24 μm have been observed, respectively. 23,24 For the case of bilayer graphene, the initial experiments on SiO 2 revealed an inverse scaling between spin and momentum relaxation times, for example, the longest spinrelaxation times were observed in the lowest-mobility devices.…”

Section: Introductionmentioning

confidence: 99%

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Electronic spin transport in dual-gated bilayer graphene

et al. 2016

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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 SiO 2 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 μm in the encapsulated bilayer, with a charge mobility of 24 000 cm 2 Vs − 1 . The carrier density dependence on the spin-relaxation time has two distinct regimes; no4 × 10 12 cm − 2 , where the spin-relaxation time decreases monotonically as the carrier concentration increases, and n ⩾ 4 × 10 12 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. INTRODUCTIONGraphene is considered to be a promising spin-channel material for future spintronics applications 1 because of its high-electronic mobility, 2 weak spin-orbit coupling 3,4 and a negligible hyperfine interaction. 5,6 The initial spin transport studies were mainly performed on single-layer 7-10 and bilayer exfoliated graphene, 9,11 and large-area graphene 12-15 deposited on conventional SiO 2 substrates. Although enhanced spin-relaxation times have been reported for bilayer graphene-based devices compared with those based on a single layer, the relatively low spin diffusion constants overall yield a lower spin-relaxation length of only 1-2 μm, 9,11 far below the theoretical predictions. 16 One approach suggested for achieving a longer distance spin communication is to increase the spin diffusion constants by fabricating higher mobility devices. 8,17 For charge transport, it has been shown that the carrier mobility of graphene devices on SiO 2 is mainly limited by interfacial charged impurities, surface roughness, and phonons. [18][19][20] The demonstration of an order-of-magnitude improvement in the mobility of graphene encapsulated between atomically flat, charge trap free boron nitride crystals 21,22 has triggered the recent spin transport studies...

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“…Graphene and h-BN share the same crystal structure and have very similar lattice constants but, unlike graphene, h-BN is an insulator with a large energy bandgap of 6 eV (7,8). Most previous studies have focused on the use of thick layers of BN as a substrate for graphene electronics (7,9,10) or as a dielectric in experiments on coupled 2D electron gases (11). HBN has also been used as a barrier for tunneling experiments: thick hBN (>6 layers) was sandwiched between two graphene layers (12) and thinner layers of this material (down to monolayer) were used in gold/hBN/gold tunneling devices (13).…”

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Electron Tunneling through Ultrathin Boron Nitride Crystalline Barriers

Britnell

Gorbachev

Jalil³

et al. 2012

Nano Lett.

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767

738

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We investigate the electronic properties of heterostructures based on ultrathin hexagonal boron nitride (h-BN) crystalline layers sandwiched between two layers of graphene as well as other conducting materials (graphite, gold). The tunnel conductance depends exponentially on the number of h-BN atomic layers, down to a monolayer thickness. Exponential behaviour of I-V characteristics for graphene/BN/graphene and graphite/BN/graphite devices is determined mainly by the changes in the density of states with bias voltage in the electrodes. Conductive atomic force microscopy scans across h-BN terraces of different thickness reveal a high level of uniformity in the tunnel current. Our results demonstrate that atomically thin h-BN acts as a defect-free dielectric with a high breakdown field; it offers great potential for applications in tunnel devices and in field-effect transistors with a high carrier density in the conductingchannel.

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Micrometer-Scale Ballistic Transport in Encapsulated Graphene at Room Temperature

Cited by 1,517 publications

References 18 publications

Controlled charge trapping by molybdenum disulphide and graphene in ultrathin heterostructured memory devices

Controlled charge trapping by molybdenum disulphide and graphene in ultrathin heterostructured memory devices

Electronic spin transport in dual-gated bilayer graphene

Electron Tunneling through Ultrathin Boron Nitride Crystalline Barriers

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