Phonon heat conduction in a semiconductor nanowire

Abstract

A model for phonon heat conduction in a semiconductor nanowire with dimensions comparable to the phonon mean free path is developed. It is based on the solution of Boltzmann's equation, which takes into account ͑i͒ modification of the acoustic phonon dispersion due to spatial confinement, and ͑ii͒ change in the nonequilibrium phonon distribution due to partially diffuse boundary scattering. Numerical simulation is performed for a silicon nanowire with boundaries characterized by different interface roughness. Phonon confinement and boundary scattering lead to a significant decrease of the lattice thermal conductivity. The value of this decrease and its interface roughness and temperature dependence are different from the predictions of the early models. The observed change in thermal resistance has to be taken into account in simulation of deep-submicron and nanometer-scale devices.

Thermal transport in phononic crystals and the observation of coherent phonon scattering at room temperature

“…impurity;j ¼ Do 4 j ðqÞ and t À 1 boundary;j ¼ Ev j ðqÞ=L, respectively, where L is the effective sample length and is a measure of the average distance between boundaries 7,19,21,22 . The constants B, C, D and E measure the fractional influence of these different types of scattering mechanisms in a given sample, and are determined by fitting equation (1) to measured bulk Si data.…”

Polar surface effects on the thermal conductivity of ZnO nanowires: a shell-like surface reconstruction-induced preserving mechanism

“…24,25,26,27,28 The thermoelectric phenomenon can be utilized to harvest otherwise wasted thermal energy directly into electric power. To increase the thermoelectric efficiency, the thermal conductivity in NWs should be reduced, which can be realized through phonon confinement effects, 29,30,31,32 isotope doping, 33 surface roughness, 34,35,36 or non-planar (kinked) structures. 37 Shi et al suggested enhancing the thermoelectric efficiency through gallium doping, and the thermoelectric figure of merit was found to be increased by a factor of 2.5 at 4% gallium doping.…”

Enhancement and reduction of one-dimensional heat conduction with correlated mass disorder

“…[1] In particular, the manipulation of the thermal conductivity in nanomaterials may enable the realization of potential applications in thermoelectric devices, solid state refrigeration and thermal cloaking. [2] One approach is to use a low-dimensional material such as nanowires [3][4][5][6] in which confinement alters the intrinsic phononic properties (e.g., anisotropy, dispersion and mean free path). The other is to use a bulk material such as Si or Ge and modify its thermal conductivity (κ) via nanostructuring.…”