Fabrication and Study of Large-Area QHE Devices Based on Epitaxial Graphene

Quantum Hall effect (QHE) devices based on epitaxial graphene films grown on SiC were fabricated and studied for development of the QHE resistance standard. The graphene-metal contacting area in the Hall devices has been improved and fabricated using a double metallization process. The tested devices had an initial carrier concentration of (0.6-10) · ~10¹¹ cm^-2 and showed half-integer QHE at a relatively low (3 T) magnetic field. The application of the photochemical gating method and annealing of the sample provides a convenient way for tuning the carrier density to the optimum value. Precision measurements of the quantum Hall resistance in graphene and GaAs devices at moderate magnetic field strengths (≤7 T) showed a relative agreement within ·10^-9.