Engineering the thermal conductivity along an individual silicon nanowire by selective helium ion irradiation

TL;DR

This paper demonstrates that selective helium ion irradiation can precisely tune the local thermal conductivity of a single silicon nanowire, enabling control over heat flow at the nanoscale for advanced thermal management applications.

Contribution

It introduces a novel method to engineer thermal conductivity at the nanoscale using controlled helium ion irradiation and provides a detailed understanding of the underlying mechanisms.

Findings

Thermal conductivity can be tuned between crystalline and amorphous limits.

A threshold dose induces a crystalline-amorphous transition.

Mechanisms involve phonon-defect scattering and defect accumulation.

Abstract

The ability to engineer the thermal conductivity of materials allows us to control the flow of heat and derive novel functionalities such as thermal rectification, thermal switching, and thermal cloaking. While this could be achieved by making use of composites and metamaterials at bulk scales, engineering the thermal conductivity at micro- and nano-scale dimensions is considerably more challenging. In this work we show that the local thermal conductivity along a single Si nanowire can be tuned to a desired value (between crystalline and amorphous limits) with high spatial resolution through selective helium ion irradiation with a well-controlled dose. The underlying mechanism is understood through molecular dynamics simulations and quantitative phonon-defect scattering rate analysis, where the behavior of thermal conductivity with dose is attributed to the accumulation and agglomeration of scattering centers at lower doses. Beyond a threshold dose, a crystalline-amorphous transition was observed.