Phonon Dispersion in <100> Si Nanowire Covered with SiO₂ Film Calculated by Molecular Dynamics Simulation

Abstract

The phonon dispersion relation in <100> Si nanowire (SiNW) is calculated by employing a realistic atomistic model surrounded by thin SiO 2 layers. We performed molecular dynamics simulation to calculate the dynamical structure factor by the space-time Fourier transform of atomic trajectories, and extracted the phonon dispersion relations. Although the bulk dispersion relations are maintained in the SiNWs on the whole, acoustic phonon branches are diffused beyond recognition, which is considered as the origin of the thermal conductivity degradation in SiNWs. A red shift of the transverse optical mode also appears probably due to the lattice strain induced by the outer oxide film. These results provide a foothold to estimate the electron-phonon scattering rates and the heat transport processes in realistic SiNWs.

Development of Interatomic Potential of Group IV Alloy Semiconductors for Lattice Dynamics Simulation

“…In the our previous work, we focus on a wave number component of k = (2π/a)(q,0,0) for 0 < q < 1, because the nanowire model has a periodicity along only the <100> ECS Transactions, 75 (8) 785-794 (2016) direction (12,16). Here a = 5.43 Å, the side length of the conventional cubic cell of the Si lattice.…”

Evaluation of thermal conductivity characteristics in Si nanowire covered with oxide by UV Raman spectroscopy

“…Recently, some researchers have reported that a decrease in thermal conductivity is caused by disorder strain induced in the SiO 2 /SiNW interface by molecular dynamics (MD) simulation. [17][18][19] Moreover, Refs. 20, 21 have reported that electrical transconductance of SiNW is enhanced by oxideinduced strain.…”

Evaluation of controlled strain in silicon nanowire by UV Raman spectroscopy

“…11,12) In addition, Zushi and coworkers have shown that a decrease in κ is caused by the disorder strain induced in SiO 2 =Si NWs by molecular dynamics (MD) simulation. [13][14][15] From these findings, to realize Si NW devices with high electric and thermoelectric performance characteristics, further improvements through the optimization of strain in the nanowires covered with an oxide film, as well as size, impurity, and crystallinity, are necessary to achieve a higher mobility and a lower κ. However, it is difficult to evaluate strain accurately during nanoscale wire fabrication by various complicated processes.…”