Abstract
Replacing GaAs by graphene to realize more practical quantum Hall resistance standards (QHRS), accurate to within 10−9 in relative value, but operating at lower magnetic fields than 10 T, is an ongoing goal in metrology. To date, the required accuracy has been reported, only few times, in graphene grown on SiC by Si sublimation, under higher magnetic fields. Here, we report on a graphene device grown by chemical vapour deposition on SiC, which demonstrates such accuracies of the Hall resistance from 10 T up to 19 T at 1.4 K. This is explained by a quantum Hall effect with low dissipation, resulting from strongly localized bulk states at the magnetic length scale, over a wide magnetic field range. Our results show that graphene-based QHRS can replace their GaAs counterparts by operating in as-convenient cryomagnetic conditions, but over an extended magnetic field range. They rely on a promising hybrid and scalable growth method and a fabrication process achieving low-electron-density devices.
Highlights
Replacing GaAs by graphene to realize more practical quantum Hall resistance standards (QHRS), accurate to within 10 À 9 in relative value, but operating at lower magnetic fields than 10 T, is an ongoing goal in metrology
From previous measurements of the Hall resistance quantization in graphene produced by various methods (exfoliation of graphite, chemical vapour deposition (CVD) on metal and Si sublimation from SiC), it was concluded that the production of graphene-based QHRS (G-QHRS) requires large graphene monolayers with homogeneous low carrier densities (o2 Â 1011 cm À 2) and high carrier mobilities (Z5,000 cm[2] V À 1 s À 1)
The combination of a large energy gap between LLs, the existence of a LL at zero energy and a moderate carrier mobility, which ensures a large mobility gap, are favourable to a wide extension of the RK/2 Hall resistance plateau, well beyond the magnetic field corresponding to vn0 1⁄4 2
Summary
Replacing GaAs by graphene to realize more practical quantum Hall resistance standards (QHRS), accurate to within 10 À 9 in relative value, but operating at lower magnetic fields than 10 T, is an ongoing goal in metrology. The Dirac physics in monolayer graphene manifests itself by a quantumpHffiffiffiffiaffiffilffilffiffiffieffiffifffifect (QHE)[7,8] with Landau levels (LLs) at energies Æ vF 2‘ neB with a 4eB/h degeneracy (valley and spin) and a sequence of Hall resistance plateaus at RH 1⁄4 ±RK/(4(n þ 1/ 2)) (with nXp0ffi)ffiffi9ffiffi.ffiffiTffi he energy spacing between the two first LLs, DEðBÞ 1⁄4 36 B1⁄2TmeV, is much larger than in GaAs (1.7B[T] meV) for currently accessible magnetic fields It results that the n 1⁄4 2 Hall resistance plateau of value RK/2 (n 1⁄4 hns/eB is the LL filling factor and ns the carrier density) can be observable even at room temperature[10].
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