Title: Thickness dependence of thermal conductivity and electron transport properties of Fe2VAl thin-films prepared by RF sputtering technique

Authors: Satoshi Hiroi; Masashi Mikami; Koichi Kitahara; Tsunehiro Takeuchi

Addresses: Faculty of Engineering, Toyota Technological Institute, 12-1, Hisakata-2, Tempaku, Nagoya, Aichi 468-8511, Japan ' National Institute of Advanced Industrial Science and Technology, 1-1-1, Umezono, Tsukuba, Ibaraki 305-8560, Japan ' Faculty of Engineering, Toyota Technological Institute, 12-1, Hisakata-2, Tempaku, Nagoya, Aichi 468-8511, Japan; Graduate School of Frontier Sciences, The University of Tokyo, 1-5, Kashiwanoha-5, Kashiwa, Chiba 277-8561, Japan ' Faculty of Engineering, Toyota Technological Institute, 12-1, Hisakata-2, Tempaku, Nagoya, Aichi 468-8511, Japan; Precursory Research for Embryonic Science and Technology, Japanese Science and Technology Agency, Gobancho-7, Chiyoda, Tokyo 102-0076, Japan; Green Mobility Collaborative Research Center, Nagoya University, Froutyou, Chikusa, Nagoya, Aichi 464-8603, Japan

Abstract: We prepared thin-films of Fe2VAl-based Heusler phase (L21 structure) by means of radio frequency magnetron sputtering technique to investigate the thickness dependence of thermoelectric properties. Epitaxial growth of L21 structure was confirmed in the samples deposited at 1073 K on single crystal magnesia substrate. Electrical resistivity and Seebeck coefficient showed weak variations, while the lattice thermal conductivity drastically decreased with decreasing thickness. The reduction of lattice thermal conductivity of the thin-films became remarkable in the samples thinner than 400 nm most likely because the mean free path of phonons was limited by the thickness of films. As a result, the figure of merit of thin-films increased significantly with decreasing thickness and showed double value of bulk sample.

Keywords: thermoelectric materials; Heusler-type Fe2VAl alloys; thin films; thermal conductivity; mean free path; phonons; thickness dependence; electron transport properties; RF sputtering; electrical resistivity; Seebeck coefficient.

DOI: 10.1504/IJNT.2016.080367

International Journal of Nanotechnology, 2016 Vol.13 No.10/11/12, pp.881 - 890

Published online: 12 Nov 2016 *

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