Comparison Between NIST Graphene and AIST GaAs Quantized Hall Devices

Several graphene quantized Hall resistance (QHR) devices manufactured at the National Institute of Standards and Technology (NIST) were compared with GaAs QHR devices and a 100-Ω standard resistor at the National Institute for Advanced Industrial Science and Technology (AIST). Measurements of a 100-Ω resistor with graphene QHR devices agreed within 5 nΩ/Ω of the values for a 100-Ω resistor obtained through GaAs measurements. The electron density of the graphene devices was adjusted at AIST to restore device properties such that operation was possible at low magnetic flux densities of 4-6 T. This adjustment was accomplished by a functionalization method utilized at NIST, allowing for consistent tunability of the graphene QHR devices with simple annealing. Such a method replaces older and less predictable methods for adjusting graphene for metrological suitability. The milestone results demonstrate the ease with which graphene can be used to make resistance comparison measurements among many National Metrology Institutes (NMIs).