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Title: From amorphous to nanocrystalline: the effect of nanograins in amorphous matrix on the thermal conductivity of hot-wire chemical-vapor deposited silicon films

Here, we have measured the thermal conductivity of amorphous and nanocrystalline silicon films with varying crystalline content from 85K to room temperature. The films were prepared by the hot-wire chemical-vapor deposition, where the crystalline volume fraction is determined by the hydrogen (H2) dilution ratio to the processing silane gas (SiH4), R=H2/SiH4. We varied R from 1 to 10, where the films transform from amorphous for R < 3 to mostly nanocrystalline for larger R. Structural analyses show that the nanograins, averaging from 2 to 9nm in sizes with increasing R, are dispersed in the amorphous matrix. The crystalline volume fraction increases from 0 to 65% as R increases from 1 to 10. The thermal conductivities of the two amorphous silicon films are similar and consistent with the most previous reports with thicknesses no larger than a few um deposited by a variety of techniques. The thermal conductivities of the three nanocrystalline silicon films are also similar, but are about 50-70% higher than those of their amorphous counterparts. The heat conduction in nanocrystalline silicon films can be understood as the combined contribution in both amorphous and nanocrystalline phases, where increased conduction through improved nanocrystalline percolation path outweighs increased interface scattering betweenmore » silicon nanocrystals and the amorphous matrix.« less
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  1. Naval Research Lab., Washington, D.C. (United States)
  2. Sotera Defense Solutions Inc., Herndon, VA (United States)
  3. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0953-8984; TRN: US1800950
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Physics. Condensed Matter
Additional Journal Information:
Journal Volume: 30; Journal Issue: 8; Journal ID: ISSN 0953-8984
IOP Publishing
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
US Department of the Navy, Office of Naval Research (ONR); USDOE
Country of Publication:
United States
36 MATERIALS SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; thermal conductivity; amorphous silicon films; nanocrystalline silicon films
OSTI Identifier: