Graphene could help make new SI standard for resistance

The quantum Hall effect provides a universal standard for electrical resistance, based on only two fundamental constants of nature: the Planck constant, h, and the elementary charge, e. At the moment, this standard is realized with excellent accuracy in semiconductor devices made from gallium arsenide, but it requires magnetic fields of around 10 teslas, ultralow temperatures of around 1 kelvin and small measurement currents of tens of microamperes. Researchers in France are now saying that devices made from high-quality graphene grown by chemical vapour deposition (CVD) on silicon carbide (SiC) do not require such stringent experimental conditions since they have measured the Hall resistance in these structures with an accuracy to within one part per billion (and below), at temperatures as high as 10 kelvin under magnetic fields of just 3.5 teslas or measurement currents as high as 0.5 mA.