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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

Journal Article · · Journal of Physics. Condensed Matter

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 between silicon nanocrystals and the amorphous matrix.

Research Organization:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Organization:
US Department of the Navy, Office of Naval Research (ONR); USDOE
Grant/Contract Number:
AC36-08GO28308
OSTI ID:
1416517
Report Number(s):
NREL/JA-5J00-70759; TRN: US1800950
Journal Information:
Journal of Physics. Condensed Matter, Vol. 30, Issue 8; ISSN 0953-8984
Publisher:
IOP PublishingCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 10 works
Citation information provided by
Web of Science

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Cited By (2)

Thermoelectric Properties of Nanocrystalline Silicon Films Prepared by Hot-Wire and Plasma-Enhanced Chemical-Vapor Depositions journal June 2019
Hierarchical nanostructuring approaches for thermoelectric materials with high power factors journal January 2019

Figures / Tables (6)