Assessment of Self-Assembled Monolayers as High-Performance Thermal Interface Materials
YL Wang and Y Cao and K Zhou and ZP Xu, ADVANCED MATERIALS INTERFACES, 4, 1700355 (2017).
Thermal interface materials (TIMs) are highly desirable for efficient thermal transfer or dissipation in a wide range of material and device applications. The self-assembled monolayers (SAMs) are promising candidates for these applications due to their high thermal transparency and structural flexibility. In this work, the performance of SAMs as practical TIMs is assessed by performing atomistic simulations. The mixed nature of diffusive and ballistic thermal transport is identified across the monolayers from signatures of coherent energy propagation and strong phonon scattering processes, respectively. The interfacial thermal conductance (ITC), G, displays remarkable dependence on the length, N, packing density, n and stretch of alkane chains. The nonmonotonic G-N relation features a peak at N = 4 that corresponds to maximum overlap of the vibrational density of states between molecular chains and substrate. When n > 0.98 mols/nm(2), phonon scattering between neighboring chains reduces the ITC. The ITC can be reduced by 32.9% under tensile strain of 23.9%, but remains almost unchanged under compression. Compared to other TIMs such as polymers, graphene, and carbon nanotubes, SAMs demonstrate simultaneously high thermal transparency and structural flexibility that can be further tailored through their molecular structures and mechanical loading conditions.
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