▎ 摘　　要

Thermal-transport properties of various graphene junctions and quantum dots with nanoscale width are systematically investigated by nonequilibrium Green's-function method. Thermal conductance is insensitive to the detailed structure of the contact region but substantially limited by the narrowest part of the systems. Thermal-contact resistance in nanodevices carved entirely from graphene is quite low (similar to 10(-10) m(2) K/W at 300 K), at least one order lower than that between graphene and other materials. Interestingly, thermal-contact resistance of double-interface junctions is just slightly higher than that of single-interface junctions, distinct from the case of electronic transport. Moreover, graphene junctions with smaller connection angles show lower thermal conductance but higher electronic conductance. The different, even opposite dependences of thermal- and electronic-transport properties on the structural characteristics may find wide applications in nanoelectronics and thermoelectricity.