Résumé
We report on measurements in large quantum Hall devices, made of high-quality graphene grown by propane/hydrogen chemical vapor deposition on SiC. These devices, having all the properties of an ideal quantum electrical resistance standard, surpass state-of-the-art GaAs/AlGaAs devices by considerable margins in their operational conditions. The Hall resistance can be found accurately quantized within one part in 10(9) over a 10-T range of magnetic fields with a lower bound at 3.5 T, temperatures as high as 10 K, or currents as high as 0.5 mA. This simplification sets the superiority of graphene for accessible and low-cost primary resistance standards.