Phonon Transmission Across Silicon Grain Boundaries by Atomistic Green's Function Method

Chen Li,Zhiting Tian

doi:10.3389/fphy.2019.00003

Abstract

Nanostructured materials are of great interest for many applications because of their special properties. Understanding the effect of grain boundaries on phonon transport in polycrystals is important for engineering nanomaterials with desired thermal transport properties. The phonon transport properties of Σ3 grain boundaries in silicon are investigated by employing atomistic Green’s function method. Results show that similar to electron transport, the perfect grain boundary does not significantly reduce the thermal conductance, while defective grain boundaries can dramatically reduce the thermal conductance. This work may be helpful for the understanding of the underlying thermal transport mechanism with grain boundaries and the design of grain boundaries for energy applications.

Highlights

Nanostructured materials are promising and attracting considerable attention because they are the fundamental building blocks for continuous technology advancement and have special properties due to the nanoscale size [1]
Based on atomistic Green’s function method, the whole system is partitioned into three regions: left lead, center region, and right lead
The 3 grain boundary is constructed as Figure 1

Summary

Introduction

Nanostructured materials are promising and attracting considerable attention because they are the fundamental building blocks for continuous technology advancement and have special properties due to the nanoscale size [1]. Polycrystals widely exist in nanostructured materials while single-crystals only form in special conditions. Polycrystals are comprised of many individual grains and grain boundaries are the interfaces between different grains. Understanding the effect of grain boundaries is critical in controlling transport properties. The effects of grain boundaries on electron mobility has been studied both experimentally [2,3,4] and theoretically [5,6,7]. Grain boundaries generally present an energy barrier to the transport of electrons and lead to a reduction of electron mobility [2, 4]. Perfect (defect-free) grain boundaries were found to be almost transparent to electron transport in highly symmetric grain boundaries [8]

Methods

Results

Conclusion