Session: 04-15-01: Nanoengineered, Nano Modified, Hierarchical, Multi-Scale Materials and Structures

Paper Number: 145893

145893 - Comparative Analysis of Different Void Shapes on Thermal Conductivity of Silicon Nanowires 

The thermal transport characteristics of phonons in silicon nanowires (SiNWs) have gained increasing significance in recent times, particularly in the context of applications involving nanoscale electronic devices, where reducing heating issues is crucial. Moreover, there has been a notable focus on the thermal transport properties of silicon nanowires (SiNWs) to develop efficient thermoelectric devices.  As the diameters of silicon nanowires (SiNWs) have reduced significantly, falling below 100 m, there is an urgent imperative to understand the thermal transport of SiNWs from an atomistic viewpoint.  Silicon nanowires (SiNWs) are highly regarded for their advantageous thermoelectric, electrical, optical, and thermal characteristics. Extensive research efforts have been directed toward the fabrication, exploration, and utilization of these nanostructures. Research shows that silicon nanowire field-effect transistors (SINW-FETs) emerge as promising candidates for biosensors due to their real-time monitoring capability, high selectivity, and exceptional sensitivity.  In silicon, heat is predominantly transported through phonon transport, a phenomenon that remains dominant even when high concentrations of charge carriers are present. Therefore, the optimization of phonon sceptering stands out as a promising strategy for effectively reducing thermal conductivity in silicon- based systems. Numerous geometrical or physical parameters can influence the thermal conductivity of SiNWs including their lateral dimensions, length, presence of defects, strain, and temperature variations. Structural defects inadvertently generated during the growth process have the potential to induce alterations in the thermal conductivity of these nanostructures.

In this study, we analyze the effect of different void shapes on the thermal conductivity of SiNWs using large-scale atomic/molecular massively parallel simulator (LAMMPS) simulations. The thermal conductivity of silicon nanowires was measured for each vacancy arrangement for a different percentage of the removed atom. Our findings demonstrate that the existence of voids considerably affects the thermal conductivity of silicon nanowires, which varies from 25% to 50% compared to pure SiNWs for different compositions. It has been found that a cuboidal void reduces thermal conductance slightly more than a spherical void. When the 2.80% atom is removed, thermal conductivity is reduced by 64.5% for the cuboidal void, which is 9% more than the spherical void. To determine the cause of this significant decrease in thermal conductivity, an analysis of the vibrational density of states (VDOS) is undertaken. It is found that the high ratio of surface area to volume leads to multiple boundary inelastic scatterings of phonons, resulting in a substantial reduction in thermal conductivity. Also, the presence of voids leads to a greater disparity in mass, resulting in reduced heat conductivity. The results suggest that including vacancy defects is an effective strategy for enhancing the thermoelectric efficiency of silicon nanowires.

Presenting Author: Titan C. Paul University of South Carolina Aiken

Presenting Author Biography: The presenter is an Associate Professor of Engineering at the University of South Carolina Aiken.

Authors:

Aninda Dey Bangladesh University of Engineering and Technology
Nafis Sadik Zim Bangladesh University of Engineering and Technology
a.k.m. Monjur Morshed Bangladesh University of Engineering and Technology
Titan C. Paul University of South Carolina Aiken