Molecular Dynamics Investigation on Thermal Conductivity and Phonon Transmission of Folded Graphene
J Gao and C Si and YR Yang and BY Cao and XD Wang, ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY, 9, 093005 (2020).
This work employs the molecular dynamics approach to investigate effects of folding on thermal conductivity of graphene that contains 86 x 60 atoms, to provide the phononics understanding for thermal conductance modulator devices constituted by the folded graphene. The spectral energy density method is utilized to perform phononics analyses. It is found that the folding significantly reduces the contribution of the TA- phonon to the thermal conductivity, so that the thermal conductivity of folded graphene is 64.42% of the one before folding. The phonon dispersion curves are analyzed to quantify the TA-phonon transmission before and after folding. It turns out that the TA-phonon lifetime of the graphene, averaging 7.57 ps before folding, is significantly reduced and only remains 4.27 ps after folding. The effects of the stress contribution and phonon mode mismatch behavior are discussed to understand how the folding affects the TA-phonon transmission. It is found that the effects of stress on the TA branch phonon transmission and the thermal conductivity are negligible. While the phonon-folding scattering should be responsible for the reduced lifetime and the decreasing thermal conductivity for folded graphene. When the phonons pass the fold, some phonons along the in-plane direction need to change from the in-plane mode into a mixed mode, and change back to an in-plane mode after passing the fold.
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