Ballistic thermoelectric properties in graphene-nanoribbon-based heterojunctions

Ballistic thermoelectric properties in graphene-nanoribbon-based heterojunctions are investigated by using the nonequilibrium Green's function approach and the Landauer transport theory. The results show that the phonon thermal conductances have similar effects for the different heterojunctions, while the electron transport is highly sensitive to the geometry details of the heterojunctions. The fluctuation of electronic transmissions can strongly enhance the thermopower. We can obtain the high thermoelectric figure of merit ZT∼0.6 at room temperature T = 300 K and ZT∼0.9 at low temperature T = 100 K by optimizing the thermopower, together with suppression of phonon transport by mismatching interface structures.