Thermal transport across graphene-mediated multilayer tungsten nanostructures

The thermal conductivity of monolayer graphene/beta-phase tungsten (beta-W) periodic stack nanostructure and the interfacial thermal resistance induced by graphene have been measured by a modified two-color femtosecond laser pump-probe technique. The thickness of beta-W films is 15, 30, 40 nm respectively, and the total thickness of periodic stack nanostructures is about 120 nm ignoring the thickness of graphene. The cross-plane thermal conductivity (k) of beta-W film is determined as 7.58 W/m K which is two orders of magnitude smaller than that of alpha-phase bulk tungsten. The small value is attributed to the vacancies in beta-W and the small grain size of beta-W, which can suppress the mean free path of hot carriers. The cross-plane thermal conductivity of periodic stack nanostructure is smaller than the value of pure W film and gradually decreases with the increasing number of graphene layers. The interfacial thermal resistance between the monolayer graphene and the tungsten films ranges from 4 x 10(-9) to 8.15 x 10(-9) m(2) K/W. The results predicted by the diffuse mismatch model are smaller than the experimental results, indicating that the phonon inelastic scattering plays an important role in the heat transport of W/graphene periodic stack nanostructure. (C) 2019 Elsevier Ltd. All rights reserved.