Effect of phonon confinement on the thermal conductivity of In0.53Ga0.47As nanofilms

Abstract

Over the past few decades, significant progress has been made to manipulate thermal transport in solids. Most of the effort has focused on reducing the phonon mean free path through boundary scattering. Herein, we demonstrate that the phonon confinement effect can also be used as a tool for managing thermal transport in solids. We measured the thermal conductivities of 10-70-nm-thick In 0.53 Ga 0.47 As nanofilms and found that the thermal conductivities decrease as the film thickness decreases. However, the reasons for this reduction differ for films with different thicknesses. The thermal conductivity of the 30-and 70-nm-thick In 0.53 Ga 0.47 As nanofilms decreases because of severe phonon boundary scattering. Our analysis indicates that phonon confinement occurs in the 10-and 20-nm-thick In 0.53 Ga 0.47 As nanofilms, which modifies phonon dispersion leading to changes in the phonon group velocity and the Debye temperature. These experimental and theoretical results could help to elucidate the phonon confinement effect in nanomaterials as well as establish a platform for understanding nanoscale thermal physics.

Strategies for Manipulating Phonon Transport in Solids

“…Therefore, theoretical analysis based on the modified υ g and the modified θ D adequately explain the experimental data. Reprinted with permission from ref . Copyright 2018 AIP Publishing.…”

“…Phonon confinement denotes phonon dispersion changes due to a phonon spatial confinement induced phonon spatial confinement induced its by its boundaries . Kim et al . reported phonon confinements in 20 and 10 nm-thick, free-standing In 0.53 Ga 0.47 As nanolayers.…”

“…Phonon confinement denotes phonon dispersion changes due to a phonon spatial confinement induced phonon spatial confinement induced its by its boundaries. 32 Kim et al 33 reported phonon confinements in 20 and 10 nm-thick, freestanding In 0.53 Ga 0.47 As nanolayers. Figure 4b shows thermal conductivities of bulk, 20, and 10 nm-thick In 0.53 Ga 0.47 As, indicated in black, blue, and red, respectively.…”

“…Therefore, theoretical analysis based on the modified υ g and the modified θ D adequately explain the experimental data. Reprinted with permission from ref 33 nanoparticles being the smallest possible, the average interparticle distance should also be the closest, leading to a reduction in the overall phonon mean free path. Similarly, Mingo et al 50 also claimed the existence of an optimum size of nanoparticles when reducing a material's thermal conductivity.…”

The role of pressure on lattice thermal conductivity and its related thermodynamical parameters in In0.53Ga0.47As nanofilms

“…Other parameters, like surface roughness and electron concentration, are determined by fitting to the experimental data 5,20 at 0 GPa. Excluding dislocations, the concentration of imperfections, such as impurities (N imp ) and electrons (N e ), remains constant across nanosizes and under varying pressures; these values, along with size-and pressure-dependent parameters, eqn ( 20)-( 34), cause modifications in this model, specifically tailored to the properties of In 0.53 Ga 0.47 As nanofilms, where (N e = 0.8 Â 10 25 m À3 ) and (N imp = 0.069 Â 10 23 m À3 ), and these values are obtained from the fitting process to the experimental data 5,20 of LTC for phonon-electron and phonon-impurity scattering rates, which are inserted into (t L (T) ph-e ) À1 and (t L(T) M ) À1 in eqn (10). New values for the first derivative, appropriate for In 0.53 Ga 0.47 As nanofilms, have been determined through a fresh derivation of the nanomaterial form (refer to Table 1).…”