Performance and Stability Assessment of Graphene-Based Quantum Hall Devices for Resistance Metrology

For more than three decades, GaAs/AlGaAs quantum Hall (QH) devices are being used as standards for the realization of the dc resistance unit ohm. Recently, the outstanding performance of graphene-based quantum Hall resistance (QHR) devices signifies an immense potential for a transition from GaAs to graphene-based devices in the field of resistance and also impedance metrology, with equally good accuracy. The recent developments in epitaxial graphene (EG) quality and fabrication of EG-based doped QHR devices and their improved performance tested in several national metrology institutes (NMIs) all over the world have demonstrated a more user-friendly dissemination of the unit ohm since they can be operated at relatively low magnetic fields and higher temperatures in comparison to existing GaAs-based devices. In this work, we have extensively tested the temporal stability of the magneto-transport properties of our graphene QH devices fabricated in the PTB and the resistance quantization performance by means of repeated high-accuracy cryogenic current comparator (CCC) measurements with several devices. Together with interlaboratory comparisons between NMI's, the performance and stability assessment demonstrate the readiness of the technology for calibration purposes in resistance metrology.