▎ 摘　　要

The thermoelectric response of high mobility (similar to 20 000 cm(2)/V s at 4 K) single layer epitaxial graphene on silicon carbide substrates has been experimentally investigated. The temperature dependence of the thermopower displays a strong deviation from the Mott relation at a carrier density of 1 x 10(12) cm(-2), reflecting the importance of the screening effect. In the quantum Hall regime, the amplitude of the thermopower peaks is lower than a quantum value, despite the high mobility of the sample. In addition, a temperature dependence for the amplitude is observed, unexpected by theories. The Nernst signal changes it sign as the magnetic field increases. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3641424]