Phonon Transport of Rough Si/Ge Superlattice Nanotubes

YH Jing and M Hu, CMC-COMPUTERS MATERIALS & CONTINUA, 38, 43-59 (2013).

Nanostructuring of thermoelectric materials bears promise for manipulating physical parameters to improve the energy conversion efficiency of thermoelectrics. In this paper the thermal transport in Si/Ge superlattice nanotubes is investigated by performing nonequilibrium molecular dynamics simulations aiming at realizing low thermal conductivity by surface roughening. Our calculations revealed that the thermal conductivity of Si/Ge superlattice nanotubes depends non-monotonically on periodic length and increases as the wall thickness increases. However, the thermal conductivity is not sensitive to the inner diameters due to the strong surface scattering at thin wall thickness. In addition, introducing roughness onto the superlattice nanotubes surface can destroy the phonon tunneling in superlattice nanotubes, which results in thermal conductivity even surpassing amorphous limit. Furthermore, a nonmonotonic dependence of the thermal conductivity of rough Si/Ge superlattice nanotubes with thicker wall thickness is found, while for thinner wall the thermal conductivity of rough Si/Ge superlattice nanotubes decreases monotonically with surface roughness increasing. Our results provide guidance for designing high performance thermoelectrics using superlattice nanotube.

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