Article abstract


Nature Materials 6, 129 - 134 (2007)
Published online: 21 January 2007 | doi:10.1038/nmat1821

Subject Categories: Electronic materials | Semiconductors

Giant thermoelectric Seebeck coefficient of a two-dimensional electron gas in SrTiO3

Hiromichi Ohta1,2,3, SungWng Kim4, Yoriko Mune1, Teruyasu Mizoguchi5, Kenji Nomura3, Shingo Ohta1, Takashi Nomura1, Yuki Nakanishi1, Yuichi Ikuhara5, Masahiro Hirano3, Hideo Hosono3,4 & Kunihito Koumoto1,2


Enhancement of the Seebeck coefficient (S ) without reducing the electrical conductivity (sigma) is essential to realize practical thermoelectric materials exhibiting a dimensionless figure of merit (ZT=S2dotsigmadotTdotkappa-1) exceeding 2, where T is the absolute temperature and kappa is the thermal conductivity. Here, we demonstrate that a high-density two-dimensional electron gas (2DEG) confined within a unit cell layer thickness in SrTiO3 yields unusually large |S|, approximately five times larger than that of SrTiO3 bulks, while maintaining a high sigma2DEG. In the best case, we observe |S|=850 muV K-1 and sigma2DEG=1.4times103 S cm-1. In addition, by using the kappa of bulk single-crystal SrTiO3 at room temperature, we estimate ZTapprox2.4 for the 2DEG, corresponding to ZTapprox0.24 for a complete device having the 2DEG as the active region. The present approach using a 2DEG provides a new route to realize practical thermoelectric materials without the use of toxic heavy elements.

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  1. Nagoya University, Graduate School of Engineering, Furo-cho, Chikusa, Nagoya 464-8603, Japan
  2. CREST, JST, 4-1-8 Honcho, Kawaguchi 332-0012, Japan
  3. ERATO-SORST, JST, in Frontier Collaborative Research Center, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
  4. Frontier Collaborative Research Center, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
  5. Institute of Engineering Innovation, The University of Tokyo, 2-11-16 Yayoi, Bunkyo, Tokyo 113-8656, Japan

Correspondence to: Hiromichi Ohta1,2,3 e-mail: h-ohta@apchem.nagoya-u.ac.jp

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