Quantum Hall resistance standards based on epitaxial graphene with <i>p</i>-type conductivity

In the last decade, quantum resistance metrology has benefited from the application of graphene as the base material for the fabrication of quantum Hall (QH) resistance standards since it allows for the realization of the resistance unit ohm in the revised International System of Units under relaxed experimental conditions. Here, we present a detailed magnetotransport investigation of p-type epitaxial graphene, which was doped by the molecular acceptor F4-TCNQ. High-accuracy measurements of the QH resistance show an excellent quantization and a reproduction of the nominal value, the half of the von Klitzing constant RK/2, within 2 nΩ/Ω. It underlines the universality of the QH effect and shows that p-type epitaxial graphene can also serve as the basis for future resistance standards for operation at relaxed experimental conditions. For the p-type devices, the onset of the QH plateau is observed at about 1 T higher magnetic fields, which can be attributed to an additional disorder or a non-symmetric charge transfer mechanism in the QH regime.