Thermal Conductance across Tungsten/Graphene Interface
Thermal transport properties between graphene and substrate remains very challenging to characterize due to the local extremely small thickness. Here, we report the thermal conductance induced by graphene (G) monolayers sandwiched between tungsten (W) films of 15, 30 and 40 nm thickness. Our systematic differential characterization is able to distinguish the thermal conductance of W film and W/G interface. The thermal conductivity (k) of the tungsten films in the cross-plane direction is determined at 1.47~2.05 Wm-1K-1. This extremely low value results from very high electron reflection (99.3%) at grain boundaries, which is also confirmed by the electrical conductivity measurement in the in-plane direction. The W/W and W/G interface thermal conductance (GW/W and GW/G) are characterized and compared using multilayered tungsten films with and without sandwiched graphene layers. The average GW/W is found to be at 280 MW m-2K-1. GW/G features variation from sample to sample, and has a lower-limit of 103 MW m-2K-1. Based on the thermal resistance fitting against the W film thickness, the W/G thermal conductance is determined as 415 MWm-2K-1, corresponding to a G2W/G value of 208 MWm-2K-1. The difference between G2W/G and GW/W uncovers the finite thermal resistance induced by the graphene layer, yet this resistance is considered very small. Compared with up-to-date reported graphene interface thermal conductance, the W/G interface is at the high end in terms of local energy coupling.
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Meng Han (POC,Primary Presenter), Iowa State University, email@example.com;
Xinwei Wang (Co-Author), Iowa State University, firstname.lastname@example.org ;