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Improvement on Thermoelectric Characteristics of Layered Nanostructure by Ion Beam Bombardment

Published online by Cambridge University Press:  01 February 2011

Bangke Zheng
Affiliation:
[email protected], Center for Irradiation Materials, , Department of Physics, Alabama A&M University, Normal, AL, P.O.Box 1447, Normal, AL, 35762, United States, 256-372-5893
S. Budak
Affiliation:
[email protected], Center for Irradiation of Materials -Alabama A & M University, P.O.Box 1447, Normal, AL, 35762, United States
C. Muntele
Affiliation:
[email protected], Center for Irradiation of Materials -Alabama A & M University, P.O.Box 1447, Normal, AL, 35762, United States
Z. Xiao
Affiliation:
[email protected], Center for Irradiation of Materials -Alabama A & M University, P.O.Box 1447, Normal, AL, 35762, United States
S. Celaschi
Affiliation:
[email protected], Center for Irradiation of Materials -Alabama A & M University, P.O.Box 1447, Normal, AL, 35762, United States
I. Mutele
Affiliation:
[email protected], Center for Irradiation of Materials -Alabama A & M University, P.O.Box 1447, Normal, AL, 35762, United States
B. Chhay
Affiliation:
[email protected], Center for Irradiation of Materials -Alabama A & M University, P.O.Box 1447, Normal, AL, 35762, United States
R. L. Zimmerman
Affiliation:
[email protected], Center for Irradiation of Materials -Alabama A & M University, P.O.Box 14 47, Normal, AL, 35762, United States
L. R. Holland
Affiliation:
[email protected], Center for Irradiation of Materials -Alabama A & M University, P.O.Box 1447, Normal, AL, 35762, United States
D. Ila
Affiliation:
[email protected], Center for Irradiation of Materials -Alabama A & M University, P.O.Box 1447, Normal, AL, 35762, United States
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Abstract

We made p-type nanoscale super lattice thermoelectric cooling devices which consist of multiple periodic layers of Si1−x Gex / Si, The thickness of each layer ranges between 10 and 50 nm. The super lattice was bombarded by 5 MeV Si ion with different fluencies aiming to form nano-cluster quantum dot structures. We estimated the thermo-electric efficiency of the so fabricated devices, measuring the thin film cross plane thermal conductivity by the 3rd harmonic method, measuring the cross plane Seebeck coefficient, and finally measuring the cross plane electric conductivity before and after ion bombardment. As predicted, the thermo-electric Figure of Merit of the films increases with increasing Si ion fluencies. In addition to the effect of quantum well confinement of the phonon transmission, the nano-scale crystal quantum dots produced by the incident Si beam further adversely affects the thermal conductivity by absorbing and dissipating phonon along the lattice, and therefore further reduces the cross plane thermal conductivity, This process increases the electron density of state therefore increasing Seebeck coefficient, and the electric conductivity.

Type
Research Article
Copyright
Copyright © Materials Research Society 2006

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