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Open AccessArticle

Thermoelectric Properties and Morphology of Si/SiC Thin-Film Multilayers Grown by Ion Beam Sputtering

1
Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523, USA
2
Manufacturing Demonstration Facility, Oak Ridge National Laboratories, Oak Ridge, TN 37831, USA
3
Plasma Controls, LLC, Fort Collins, CO 80526, USA
4
Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
*
Author to whom correspondence should be addressed.
Coatings 2018, 8(3), 109; https://doi.org/10.3390/coatings8030109
Received: 6 February 2018 / Revised: 2 March 2018 / Accepted: 6 March 2018 / Published: 19 March 2018
(This article belongs to the Special Issue Novel Thin Film Materials for Thermoelectric Applications)
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Abstract

Multilayers (MLs) of 31 bi-layers and a 10-nm layer thickness each of Si/SiC were deposited on silicon, quartz and mullite substrates using a high-speed, ion-beam sputter deposition process. The samples deposited on the silicon substrates were used for imaging purposes and structural verification as they did not allow for accurate electrical measurement of the material. The Seebeck coefficient and the electrical resistivity on the mullite and the quartz substrates were reported as a function of temperature and used to compare the film performance. The thermal conductivity measurement was performed for ML samples grown on Si, and an average value of the thermal conductivity was used to find the figure of merit, zT, for all samples tested. X-ray diffraction (XRD) spectra showed an amorphous nature of the thin films. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the film morphology and verify the nature of the crystallinity. The mobility of the multilayer films was measured to be only 0.039 to 1.0 cm2/Vs at room temperature. The samples were tested three times in the temperature range of 300 K to 900 K to document the changes in the films with temperature cycling. The highest Seebeck coefficient is measured for a Si/SiC multilayer system on quartz and mullite substrates and were observed at 870 K to be roughly −2600 μV/K due to a strain-induced redistribution of the states’ effect. The highest figure of merit, zT, calculated for the multilayers in this study was 0.08 at 870 K. View Full-Text
Keywords: thin-film thermoelectric; Si/SiC multilayers; giant Seebeck thin-film thermoelectric; Si/SiC multilayers; giant Seebeck
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Cramer, C.L.; Farnell, C.C.; Farnell, C.C.; Geiss, R.H.; Williams, J.D. Thermoelectric Properties and Morphology of Si/SiC Thin-Film Multilayers Grown by Ion Beam Sputtering. Coatings 2018, 8, 109.

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