We report high-precision resistance measurements on quantum Hall resistance devices fabricated from uniform epitaxial graphene grown by propane-hydrogen chemical vapor deposition on a two-inch silicon carbide substrate. Through molecular doping, we achieve a low carrier density regime (ns 1.5 × 1011 cm−2) combined with high mobility (μ ≥ 6000 cm2 V−1 s−1) at low temperature. Accurate quantization of the Hall resistance is demonstrated at magnetic flux densities as low as 3.5 T, temperatures up to 8 K, and measurement currents up to 325 μA, with relative measurement uncertainties of a few parts per billion. A stability diagram mapping dissipation as a function of temperature and current provides insight into optimal doping conditions that maximize the breakdown current. All measurements were carried out in a pulse-tube-based cryomagnetic system, enabling simplified and continuous operation of the quantum Hall resistance standard without liquid helium consumption.
Couëdo et al. (Mon,) studied this question.