Coherent and incoherent effects of nanopores on thermal conductance in silicene
L Cui and GS Wei and Z Li and JJ Ma and XZ Du, INTERNATIONAL JOURNAL OF THERMAL SCIENCES, 167, 107009 (2021).
A fundamentally new approach of manipulating thermal properties is utilizing the wave nature of phonons, which can be realized by introducing secondary artificial periodicity in nanostructures. In this paper, we have studied the heat transport in silicene nanomesh (SNM, a silicene sheet with periodically arranged nanopores), using first- principles calculations and molecular dynamics simulations. The results show the thermal conductivity of SNM is obviously lower than that of silicene. Combining with the analysis of wave and particle characteristics of phonons, we reveal the main reasons responsible for the reduction in thermal conductivity of SNM. The coherent Bragg scattering from the secondary artificial periodicity leads to the reduction in phonon group velocities of LA and optical phonons. Different from the graphene nanomesh reported previously, multiple phonon bandgaps in the optical phonon spectrum of SNM are found for the first time. Moreover, it is noticed that, phonons are scattered not only at the hole boundaries, but also at the interface between the surface and interfacial regions in SNMs. In particular, the out-of-plane vibrations are easier to be scattered at the interface than the in-plane vibrations. This study uncovers the coherent and incoherent phonon transport in SNMs, which would deepen our understanding on heat conduction and shed light on the development of Si-based nanoelectronic devices.
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