Precision comparison of the quantum Hall effect in graphene and gallium arsenide

Janssen, T. J. B. M.; Williams, Jonathan M. J.; Fletcher, Nick; Goebel, R; Tzalenchuk, Alexander; Yakimova, Rositza; Lara‐Avila, Samuel; Kubatkin, Sergey; Fal’ko, Vladimir I.

doi:10.1088/0026-1394/49/3/294

Cited by 68 publications

(64 citation statements)

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“…Since grain sizes in graphene made by chemical vapor deposition are usually small, this may help explain why the quantum Hall effect is usually poorly developed in devices made of this material. The half-integer quantum Hall effect (QHE) [1,2] in monolayer graphene grown on silicon-carbide substrates has been observed to metrological accuracy [3][4][5]. Very high breakdown currents have been recorded, and quantization remains accurate also at elevated temperatures.…”

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Influence of [0001] tilt grain boundaries on the destruction of the quantum Hall effect in graphene

2015

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The reason why the half-integer quantum Hall effect (QHE) is suppressed in graphene grown by chemical vapor deposition (CVD) is unclear. We propose that it might be connected to extended defects in the material and present results for the quantum Hall effect in graphene with [0001] tilt grain boundaries connecting opposite sides of Hall bar devices. Such grain boundaries contain 5-7 ring complexes that host defect states that hybridize to form bands with varying degree of metallicity depending on grain boundary defect density. In a magnetic field, edge states on opposite sides of the Hall bar can be connected by the defect states along the grain boundary. This destroys Hall resistance quantization and leads to non-zero longitudinal resistance. Anderson disorder can partly recover quantization, where current instead flows along returning paths along the grain boundary depending on defect density in the grain boundary and on disorder strength. Since grain sizes in graphene made by chemical vapor deposition are usually small, this may help explain why the quantum Hall effect is usually poorly developed in devices made of this material. The half-integer quantum Hall effect (QHE) [1,2] in monolayer graphene grown on silicon-carbide substrates has been observed to metrological accuracy [3][4][5]. Very high breakdown currents have been recorded, and quantization remains accurate also at elevated temperatures. This material may therefore be the next choice for an improved resistance standard. On the other hand, QHE plateaux have not been measured to the same level of accuracy on Hall bars made of graphene grown by chemical vapor deposition (CVD) [6,7]. The reason for this disparity is unclear, but it may be due to extrinsic effects, such as defects and inhomogeneity introduced in the process of graphene transfer from substrates used in the growth to other substrates used for devices, or due to defects in the material itself, such as grain boundaries that usually are found in graphene made by CVD [8].In a recent experiment [7], it was indeed argued that grain boundaries may be the source of reduced quantization in devices made of CVD graphene. A clear theoretical picture of how the QHE is destroyed in graphene with grain boundaries is however still lacking. One particular and very special type of grain boundary has been considered theoretically in the literature before [7,9]. The grain boundary consists of a perfect row of 5-8-5 ring complexes that separates two perfect armchair ribbons oriented along the same axis. To join the armchair ribbons to the grain boundary, the ribbons are cut at 90• to their armchair edges so that perfect zigzag edges are formed. These zigzag edges can be attached to the grain boundary. In a magnetic field, a picture appears of current flowing along an armchair edge in the ribbon and along a zigzag edge along the grain boundary over to the opposite edge of the ribbon where the current can flow back in the opposite direction. This special type of grain boundary is not the only or typical grain...

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Influence of [0001] tilt grain boundaries on the destruction of the quantum Hall effect in graphene

2015

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“…3 In particular, graphene grown on the Si-face of SiC (SiC/G) has been the material of choice for the fabrication of graphene-based high performance electronic devices such as high-frequency analogue transistors, 4 sensors, 5 and quantum resistance standards. [6][7][8][9][10] In SiC/G, the two-dimensional system is formed by graphene situated on top of a non-conducting buffer carbon layer (the 0-layer), covalently bonded to SiC. Charge transfer between graphene and the localised donor states in the buffer, driven by the work function difference A $ 1 eV, leads to a significant electron density in the as grown SiC/G, typically n $ 10 13 cm À2 .…”

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“…11 On the other hand, the SiC/G-substrate charge transfer leads to a robust quantum Hall quantization, making this material a superior embodiment of the quantum resistance standard compared to conventional GaAs heterostructures. 7,12 Charge transfer from the substrate manifests in quantum magnetotransport as anomalously wide quantum Hall plateaux and high breakdown currents that have lead to the most accurate resistance quantization measurements to-date. 7 The ideal technique for carrier density control would preserve the rich interplay between the graphene layer and the substrate.…”

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“…7,12 Charge transfer from the substrate manifests in quantum magnetotransport as anomalously wide quantum Hall plateaux and high breakdown currents that have lead to the most accurate resistance quantization measurements to-date. 7 The ideal technique for carrier density control would preserve the rich interplay between the graphene layer and the substrate. The standard graphene field-effect transistor (GFET) configuration applied to epitaxial graphene shows promise for transistor applications, but, as far as precision metrology is concerned, suffers from unacceptable gate dielectric leakage, up to nanoamperes per square micrometre of the gate area, even at modest voltages of a few volts.…”

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Tuning carrier density across Dirac point in epitaxial graphene on SiC by corona discharge

Lartsev

Yager

Bergsten

et al. 2014

Applied Physics Letters

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We demonstrate reversible carrier density control across the Dirac point (Delta n similar to 10(13) cm(-2)) in epitaxial graphene on SiC (SiC/G) via high electrostatic potential gating with ions produced by corona discharge. The method is attractive for applications where graphene with a fixed carrier density is needed, such as quantum metrology, and more generally as a simple method of gating 2DEGs formed at semiconductor interfaces and in topological insulators.

Funding Agencies|Graphene Flagship [CNECT-ICT-604391]; Swedish Foundation for Strategic Research (SSF); Linnaeus Centre for Quantum Engineering; Knut and Allice Wallenberg Foundation; Chalmers AoA Nano; NMS (UK); EMRP project GraphOhm; EMRP within EURAMET; European Union

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“…4 The observation of the quantum Hall effect in graphene presented exciting new opportunities for metrology, 1,5 since the unique electronic structure of graphene leads to an exceptionally robust QHE, observable even at room temperature. 6 In a recent direct comparison experiment between SiC/G and GaAs (the present system of choice for QHR), 2 the QHR was found to agree with a relative uncertainty of 10 −10 . The accuracy of this comparison was limited by the lower breakdown current in the GaAs device (i.e.…”

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confidence: 78%

Low contact resistance in epitaxial graphene devices for quantum metrology

et al. 2015

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We investigate Ti/Au contacts to monolayer epitaxial graphene on SiC (0001) for applications in quantum resistance metrology. Using three-terminal measurements in the quantum Hall regime we observed variations in contact resistances ranging from a minimal value of 0.6 Omega up to 11 k Omega. We identify a major source of high-resistance contacts to be due bilayer graphene interruptions to the quantum Hall current, whilst discarding the effects of interface cleanliness and contact geometry for our fabricated devices. Moreover, we experimentally demonstrate methods to improve the reproducibility of low resistance contacts (less than 10 Omega) suitable for high precision quantum resistance metrology.

Funding Agencies|Graphene Flagship [CNECT-ICT-604391]; Swedish Foundation for Strategic Research (SSF); Linnaeus Centre for Quantum Engineering; Knut and Alice Wallenberg Foundation; Chalmers AoA Nano; Swedish-Korean Basic Research Cooperative Program of the NRF [2014R1A2A1A1 2067266]; EMRP project GraphOhm; EMRP within EURAMET; EMRP within European Union

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Precision comparison of the quantum Hall effect in graphene and gallium arsenide

Cited by 68 publications

References 45 publications

Influence of [0001] tilt grain boundaries on the destruction of the quantum Hall effect in graphene

Influence of [0001] tilt grain boundaries on the destruction of the quantum Hall effect in graphene

Tuning carrier density across Dirac point in epitaxial graphene on SiC by corona discharge

Low contact resistance in epitaxial graphene devices for quantum metrology

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