Phonons and Thermal Transport in Si/SiO2 Multishell Nanotubes: Atomistic Study

Abstract

Thermal transport in the Si/SiO2 multishell nanotubes is investigated theoretically. The phonon energy spectra are obtained using the atomistic lattice dynamics approach. Thermal conductivity is calculated using the Boltzmann transport equation within the relaxation time approximation. Redistribution of the vibrational spectra in multishell nanotubes leads to a decrease of the phonon group velocity and the thermal conductivity as compared to homogeneous Si nanowires. Phonon scattering on the Si/SiO2 interfaces is another key factor of strong reduction of the thermal conductivity in these structures (down to 0.2 Wm−1K−1 at room temperature). We demonstrate that phonon thermal transport in Si/SiO2 nanotubes can be efficiently suppressed by a proper choice of nanotube geometrical parameters: lateral cross section, thickness and number of shells. We argue that such nanotubes have prospective applications in modern electronics, in cases when low heat conduction is required.

Record High Power Factor and Low Thermal Conductivity in Amorphous/PbTe/Amorphous Multiple Quantum Wells

“…According to previous theoretical and experimental results, thermal conductivity as low as the amorphous limit or even lower can be achieved in SLs with amorphous layers. [54][55][56][57][58] In [(PbTe)n/𝛼-STO]22 MQWs, phonon scattering happened at interfaces due to diffuse interface scattering (in the incoherent regime where phonons behave like particles [59] ). Thus, interfacial roughness is generally considered as another source of diffuse interface scattering since phonons see more interfaces to scatter at (illustrated schematically in Figure 7c).…”