Theoretical Study on Magnetoelectric and Thermoelectric Properties for Graphene Devices

Two of our recent theoretical efforts on elucidating the functions of graphene are reported. A first-principles calculation of the growth process of graphene islands on SiC(0001) shows that an embedded structure is energetically preferable. Island with this embedded structure do not have any broken dangling bonds at their edges. Their electronic states clearly show that they surely act as islands. Islands with zigzag edges have edge-localized states, which causes magnetoelectric effects. Graphene is also expected as a highly efficient material for thermoelectric elements according to a theoretical study. If the carrier scattering sources are adequately suppressed, the thermoelectric figure of merit greatly exceeds 1 at temperatures higher than 300 K with the Fermi energy fixed around the Dirac point. Since graphene is cheaper, resource abundant, more harmless, higher in melting temperature, and much lighter in density, than the present typical material, BiTe/Sb, many new applications could be considered.