Strain effect analysis on phonon thermal conductivity of two-dimensional nanocomposites

Abstract

In this paper, we present a model that combines lattice dynamics and the phonon Boltzmann transport equation (BTE) to analyze strain effect on the cross-plane phonon thermal conductivity of silicon wire-germanium host nanocomposites. For a given strain condition, mechanical strain is translated to crystal lattice deformation by using the Cauchy–Born rule. Strain-dependent phonon thermal properties of Si and Ge obtained from lattice dynamics with Tersoff empirical interatomic potential are then incorporated into the BTE, in which ballistic transport within one material and diffuse scattering between Si–Ge interface are employed. The strain-dependent BTE is solved numerically on an unstructured triangular mesh by using a finite volume method. Nanocomposites with different Si nanowire cross sections are also investigated. The results show that the phonon thermal conductivity of the nanocomposites can be significantly decreased (or increased) by a tensile (or compressive) strain. With the same length change, hydrostatic strain produces a larger variation in phonon thermal conductivity than uniaxial strain. In addition, it is shown that with the same atomic percentage, the cross-sectional shape makes little difference to the thermal conductivity except at very small characteristic lengths of the Si nanowire.

Thermal conductivity of strained silicon: Molecular dynamics insight and kinetic theory approach

“…More importantly we notice that the general trend of κ(ε h ) variations obtained with Tersoff III potential, plotted in Fig. 2, is similar to the previously reported strain effects on the thermal conductivity of bulk silicon 7,11,15 and Si nanostructures 64,65 .…”

Colloquium: Phononic thermal properties of two-dimensional materials

“…The experimental demonstration of utilizing strain to actively control phonon and thermal properties has been applied to many different kinds of material systems (Hsieh, et al, 2009;Hsieh, et al, 2011;Alam, et al, 2015). Theoretical studies have also been performed to understand the origins of strain-dependent thermal conductivity of both bulk crystals (Picu, et al, 2003;Bhowmick and Shenoy, 2006;Li, et al, 2010;Parrish, et al, 2014) and nanostructured materials (Xu and Li, 2009;Xu and Buehler, 2009;Li, et al, 2010). While it is necessary to quantify the strain dependence of thermal conductivity, it is still more challenging to precisely control the exerted strain in 2-D materials than in 3-D materials.…”

Influence of Prestress Fields on the Phonon Thermal Conductivity of GaN Nanostructures

“…The strain effects on the thermal conductivity in thin films and insulating solids have been explored by using molecular dynamic simulations [27][28][29]. The thermal conductivity of strained nanostructures such as two-dimensional nanocomposites, nanowires, and nanofilms also have been modeled and analyzed by the atomic method and continuum models [30][31][32]. The more relevant studies of straindependent thermal conductivity in GaN nanostructures revealed that the deformation along the axial directions of wires reduces the thermal conductivity linearly both in rectangular and triangu lar GaN nanowires [33,34], More recently, an experimental study has shown the strong strain-thermal conductivity coupling in the SiN thin film [35], For the sake of giving more complete insights into the strain/ stress-thermal conductivity coupling behavior in GaN nanostruc tures, it is cardinal that various deformation modes are needed to examined since the nanostructures could experience complex strain/stress circumstances in corresponding electronic devices.…”