Phonon–boundary scattering in ultrathin single-crystal silicon layers

Abstract

Thermal engineering of many nanoscale sensors, actuators, and high-density thermomechanical data storage devices, as well as the self-heating in deep submicron transistors, are largely influenced by thermal conduction in ultrathin silicon layers. The present study measures the lateral thermal conductivity of single-crystal silicon layers of thicknesses 20 and 100 nm at temperatures between 20 and 300 K, using Joule heating and electrical–resistance thermometry in suspended microfabricated structures. The thermal conductivity of the 20 nm thick silicon layer is ∼22 W m−1 K−1, which is nearly an order of magnitude smaller than the bulk value at room temperature. In general, a large reduction in thermal conductivity resulting from phonon–boundary scattering, particularly at low temperatures, is observed. It appears that the classical thermal conductivity theory that accounts for the reduced phonon mean-free paths based on a solution of the Boltzmann transport equation along a layer is able to capture the ballistic, or nonlocal, phonon transport in ultrathin silicon films.

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

“…In this formulation, assuming a sufficiently large sample thickness [23][24][25][26] and feature sizes 13 , if coherent boundary scattering were absent, the Si phonon dispersion would remain basically unaltered before and after the PnC patterning and fixing L c would lead to a constant incoherent boundary scattering limit (Supplementary Table 1). We thus set out to realize an experiment where the geometry of the PnC lattice is varied, while L c is kept constant.…”

Atomistic origin of the reduced lattice thermal conductivity of silicon nanotubes

“…Clearly, our predictions are consistent with theoretical calculations 29,34 and experimental measurements. [37][38][39] The physical origin of this issue is that the phonon-boundary scattering becomes stronger when the thickness is reduced to the nanoscale, which causes the huge reduction of thermal conductivity. Also, the temperature-dependent thermal conductivities of SiNFs at fixed thicknesses of 1600, 830, 420, 100 and 20 nm are shown in Fig.…”

Non-local effects in radial heat transport in silicon thin layers and graphene sheets

“…These systems have been much studied theoretically (Alvarez et al 2009(Alvarez et al , 2011 and experimentally (Asheghi et al 1997;Ju & Goodson 1999;Liu & Asheghi 2004;Saito et al 2007;Balandin et al 2008;Ghosh et al 2008;Balandin 2011). However, the thermodynamical behaviour in…”