Thermal Conductivity of Amorphous and Nanocrystalline Silicon Films Prepared by Hot-Wire Chemical-Vapor Deposition: Article No. 014206

William Nemeth, B. Jugdersuren, B. Kearney, D. Queen, T. Metcalf, J. Culbertson, C. Chervin, R. Stroud, Q. Wang, Xiao Liu

Research output: Contribution to journalArticlepeer-review

25 Scopus Citations

Abstract

We report 3..omega.. thermal conductivity measurements of amorphous and nanocrystalline silicon thin films from 85 to 300 K prepared by hot-wire chemical-vapor deposition, where the crystallinity of the films is controlled by the hydrogen dilution during growth. The thermal conductivity of the amorphous silicon film is in agreement with several previous reports of amorphous silicon prepared by a variety of deposition techniques. The thermal conductivity of the as-grown nanocrystalline silicon film is 70% higher and increases 35% more after an anneal at 600 degrees C. They all have similarly weak temperature dependence. Structural analysis shows that the as-grown nanocrystalline silicon is approximately 60% crystalline, nanograins and grain boundaries included. The nanograins, averaging 9.1 nm in diameter in the as-grown film, are embedded in an amorphous matrix. The grain size increases to 9.7 nm upon annealing, accompanied by the disappearance of the amorphous phase. We extend the models of grain boundary scattering of phonons with two different non-Debye dispersion relations to explain our result of nanocrystalline silicon, confirming the strong grain size dependence of heat transport for nanocrystalline materials. However, the similarity in thermal conductivity between amorphous and nanocrystalline silicon suggests the heat transport mechanisms in both structures may not be as dissimilar as we currently understand.
Original languageAmerican English
Number of pages8
JournalPhysical Review B
Volume96
Issue number1
DOIs
StatePublished - 2017

NREL Publication Number

  • NREL/JA-5J00-69127

Keywords

  • thermal conductivity
  • thin films

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