University of Illinois Urbana-Champaign

Investigating Thermoelectric Effect in Bulk Si and Si Nanowire

Li, Ran

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Description

Title
Investigating Thermoelectric Effect in Bulk Si and Si Nanowire
Author(s)
Li, Ran
Contributor(s)
Ravaioli, Umberto
Issue Date
2012-05
Keyword(s)
  • thermoelectric effect
  • nanowires
  • silicon nanowires
  • device modeling
Abstract
In this research, the efficiency of thermoelectric effect in different dimensions is investigated. The efficiency is measured by figure of merit ZT, which is proportional to the power factor including the Seebeck coefficient and electrical conductivity and inversely proportional to thermal conductivity. According to the Landauer formalism, all the electronic performance parameters could be compared among 3D, 2D and 1D. The 1D material shows a high power factor per effective conducting channel, but this advantage could not be put in practice due to the challenge of nanowire package density. Our research focuses on the thermal conductivity calculation in bulk Si and Si Nanowire at temperatures 20-350K. The simple Debye model is used to calculate the bulk Si conductivity but does not produce the good match with experimental results. Good agreement with experimental results is achieved in bulk Si through choosing a more exact scattering mechanism formula and using the Callaway formula in bulk Si. Due to the confinement of phonon mean free path, the thermal conductivity is reduced greatly in Si Nanowire. The boundary scattering rate increases dramatically and becomes the dominant scattering mechanism. The similar scattering mechanisms are chosen in Si Nanowire except the boundary scattering got slightly adjusted due to specular or diffuse scattering on the surface. The theoretical results match the experimental results with 115 nm, 56 nm and 37 nm diameters Si Nanowire very well except for small differences at very low temperature ranges. investigated. The efficiency is measured by figure of merit ZT, which is proportional to the power factor including the Seebeck coefficient and electrical conductivity and inversely proportional to thermal conductivity. According to the Landauer formalism, all the electronic performance parameters could be compared among 3D, 2D and 1D. The 1D material
Type of Resource
text
Language
en
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http://hdl.handle.net/2142/46499

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