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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

Thermal Transport in Silicon Nanowires at High Temperatures




Abstract

Thermal transport in silicon nanowires has captured the attention of theoretical scientists for understanding phonon transport at the nanoscale, and the thermoelectric figure-of-merit reported in rough nanowires has inspired engineers to develop cost-effective waste heat recovery systems. Thermoelectric power generators composed of silicon target high-temperature applications due to improved efficiency beyond 550 K, and there remain unanswered questions regarding the impact of surface boundaries and varying mode contributions as the highest vibrational modes are activated (the Debye temperature of silicon is 645 K). Here we present a technique to investigate thermal transport in individual nanowires at high temperatures up to 700 K. We use high-purity silicon nanowires and thermal transport models to assess the unique features of high-temperature phonons including the optical mode contribution. We verify temperature-dependent thermal transport in rough silicon nanowires using established synthesis techniques, which allow investigation of surface roughness effects with respect to vertical and lateral roughness scales. The rough nanowires show a significant thermal conductivty reduction throughout the temperature range (20 K – 700 K), demonstrating a potential for efficient power generation. The metrology opens up opportunities to study high-temperature phenomena in nanomaterials including one- and two-dimensional structures. New findings may make significant advances in high-temperature relevant energy conversion systems such as thermoelectric power generators.

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