▎ 摘　　要

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) . 10(11) 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 (