Using Mosaicity to Tune Thermal Transport in Polycrystalline AlN Thin Films

Shivkant Singh, Shahab Shervin, Haiding Sun, Milad Yarali, Jie Chen, Ronghui Lin, Kuang-Hui Li, Xiaohang Li, Jae-Hyun Ryou, Anastassios Mavrokefalos

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8 Scopus citations

Abstract

The effect of controlling the c-axis alignment (mosaicity) to the cross-plane thermal transport in textured polycrystalline aluminum nitride (AlN) thin films is experimentally and theoretically investigated. We show that by controlling the sputtering conditions we are able to deposit AlN thin films with varying c-axis grain tilt (mosaicity) from 10° to 0°. Microstructural characterization shows that the films are nearly identical in thickness and grain size, and the difference in mosaicity alters the grain interface quality. This has a significant effect to thermal transport where a thermal conductivity of 4.22 W/mK vs. 8.09 W/mK are measured for samples with tilt angles of 10° vs. 0° respectively. The modified Callaway model was used to fit the theoretical curves to the experimental results using various phonon scattering mechanisms at the grain interface. It was found that using a non-gray model gives an overview of the phonon scattering at the grain boundaries, whereas treating the grain boundary as an array of dislocation lines with varying angle relative to the heat flow, best describes the mechanism of the thermal transport. Lastly, our results show that controlling the quality of the grain interface provides a tuning knob to control thermal transport in polycrystalline materials.
Original languageEnglish (US)
Pages (from-to)20085-20094
Number of pages10
JournalACS Applied Materials & Interfaces
Volume10
Issue number23
DOIs
StatePublished - May 17 2018

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