Interface Energy Coupling between β-tungsten Nanofilm and Few-layered Graphene

We report the thermal conductance induced by few-layered graphene (G) sandwiched between β -phase tungsten ( β -W) films of 15, 30 and 40 nm thickness. Our differential characterization is able to distinguish the thermal conductance of β -W film and β -W/G interface. The cross-plane thermal conductivity ( k ) of β -W films is determined at 1.69~2.41 Wm −1 K −1 which is much smaller than that of α -phase tungsten (174 Wm −1 K −1 ). This small value is consistent with the large electrical resistivity reported for β -W in literatures and in this work. The β -W/ β -W and β -W/G interface thermal conductance ( G W/W and G W/G ) are characterized and compared using multilayered β -W films with and without sandwiched graphene layers. The average G W/W is found to be at 280 MW m −2 K −1 . G W/G features strong variation from sample to sample, and has a lower-limit of 84 MW m −2 K −1 , taking into consideration of the uncertainties. This is attributed to possible graphene structure damage and variation during graphene transfer and W sputtering. The difference between G 2 W/G and G W/W uncovers the finite thermal resistance induced by the graphene layer. Compared with up-to-date reported graphene interface thermal conductance, the β -W/G interface is at the high end in terms of local energy coupling.