title: Quenched phonon drag in silicon nanowires reveals significant effect in the bulk at room temperature.
abstract: Existing theory and data cannot quantify the contribution of phonon drag to the Seebeck coefficient (S) in semiconductors at room temperature. We show that this is possible through comparative measurements between nanowires and the bulk. Phonon boundary scattering completely quenches phonon drag in silicon nanowires enabling quantification of its contribution to S in bulk silicon in the range 25-500 K. The contribution is surprisingly large (∼34%) at 300 K even at doping of ∼3 × 10(19) cm(-3). Our results contradict the notion that phonon drag is negligible in degenerate semiconductors at temperatures relevant for thermoelectric energy conversion. A revised theory of electron-phonon momentum exchange that accounts for a phonon mean free path spectrum agrees well with the data.
authors.affiliation: †Department of Mechanical Science and Engineering, ‡Department of Electrical and Computer Engineering, and §Micro and Nanotechnology Laboratory, University of Ilinois at Urbana-Champaign, Urbana Illinois 61801, United States.
authors.forename: Jyothi
authors.initials: J
authors.lastname: Sadhu
authors.affiliation: †Department of Mechanical Science and Engineering, ‡Department of Electrical and Computer Engineering, and §Micro and Nanotechnology Laboratory, University of Ilinois at Urbana-Champaign, Urbana Illinois 61801, United States.
authors.forename: Hongxiang
authors.initials: H
authors.lastname: Tian
authors.affiliation: †Department of Mechanical Science and Engineering, ‡Department of Electrical and Computer Engineering, and §Micro and Nanotechnology Laboratory, University of Ilinois at Urbana-Champaign, Urbana Illinois 61801, United States.
authors.forename: Jun
authors.initials: J
authors.lastname: Ma
authors.affiliation: †Department of Mechanical Science and Engineering, ‡Department of Electrical and Computer Engineering, and §Micro and Nanotechnology Laboratory, University of Ilinois at Urbana-Champaign, Urbana Illinois 61801, United States.
authors.forename: Bruno
authors.initials: B
authors.lastname: Azeredo
authors.affiliation: †Department of Mechanical Science and Engineering, ‡Department of Electrical and Computer Engineering, and §Micro and Nanotechnology Laboratory, University of Ilinois at Urbana-Champaign, Urbana Illinois 61801, United States.
authors.forename: Junhwan
authors.initials: J
authors.lastname: Kim
authors.affiliation: †Department of Mechanical Science and Engineering, ‡Department of Electrical and Computer Engineering, and §Micro and Nanotechnology Laboratory, University of Ilinois at Urbana-Champaign, Urbana Illinois 61801, United States.
authors.forename: Karthik
authors.initials: K
authors.lastname: Balasundaram
authors.affiliation: †Department of Mechanical Science and Engineering, ‡Department of Electrical and Computer Engineering, and §Micro and Nanotechnology Laboratory, University of Ilinois at Urbana-Champaign, Urbana Illinois 61801, United States.
authors.forename: Chen
authors.initials: C
authors.lastname: Zhang
authors.affiliation: †Department of Mechanical Science and Engineering, ‡Department of Electrical and Computer Engineering, and §Micro and Nanotechnology Laboratory, University of Ilinois at Urbana-Champaign, Urbana Illinois 61801, United States.
authors.forename: Xiuling
authors.initials: X
authors.lastname: Li
authors.affiliation: †Department of Mechanical Science and Engineering, ‡Department of Electrical and Computer Engineering, and §Micro and Nanotechnology Laboratory, University of Ilinois at Urbana-Champaign, Urbana Illinois 61801, United States.
authors.forename: P M
authors.initials: PM
authors.lastname: Ferreira
authors.affiliation: †Department of Mechanical Science and Engineering, ‡Department of Electrical and Computer Engineering, and §Micro and Nanotechnology Laboratory, University of Ilinois at Urbana-Champaign, Urbana Illinois 61801, United States.
authors.forename: S
authors.initials: S
authors.lastname: Sinha
keywords: Seebeck effect; electron−phonon scattering; phonon drag; silicon nanowires; thermoelectrics