Unusually Large Enhancement of Thermopower in an Electric Field Induced Two‐Dimensional Electron Gas

Two-dimensionally confined electrons showing unusually large thermopower (S) have attracted attention as a potential approach for developing high performance thermoelectric materials. However, enhanced S has never been observed in electric field induced two-dimensional electron gas (2DEG). Here we demonstrate electric field modulation of S for a field effect transistor (FET) fabricated on a SrTiO3 crystal using a water-infiltrated nanoporous glass as the gate insulator. An electric field application confined carrier electrons up to ~2E15 /cm^2 in an extremely thin (~2 nm) 2DEG. Unusually large enhancement of |S| was observed when the sheet carrier concentration exceeded 2.5E14 /cm^2, and it modulated from ~600 (~2E15 /cm^2) to ~950 {\mu}V/K (~8E14 /cm^2), which were approximately five times larger than those of the bulk, clearly demonstrating that an electric field induced 2DEG provides unusually large enhancement of |S|.

[1]  H. Ohta,et al.  Field-modulated thermopower in SrTiO3-based field-effect transistors with amorphous 12CaO⋅7Al2O3 glass gate insulator , 2009 .

[2]  G. Poon,et al.  Chapter 2 Electronic and thermoelectric properties of Half-Heusler alloys , 2001 .

[3]  K. Pernstich,et al.  Field-effect-modulated Seebeck coefficient in organic semiconductors. , 2008, Nature materials.

[4]  G. J. Snyder,et al.  Disordered zinc in Zn4Sb3 with phonon-glass and electron-crystal thermoelectric properties , 2004, Nature materials.

[5]  Hideo Hosono,et al.  Giant thermoelectric Seebeck coefficient of a two-dimensional electron gas in SrTiO3. , 2007, Nature materials.

[6]  H. Ohta,et al.  Field-induced water electrolysis switches an oxide semiconductor from an insulator to a metal , 2010, Nature communications.

[7]  H. Ohta Thermoelectrics based on strontium titanate , 2007 .

[8]  N. Mott,et al.  Observation of Anderson Localization in an Electron Gas , 1969 .

[9]  Peidong Yang,et al.  Field-effect modulation of Seebeck coefficient in single PbSe nanowires. , 2009, Nano letters.

[10]  G. Kotliar,et al.  Peierls distortion as a route to high thermoelectric performance in In4Se3-δ crystals , 2009, Nature.

[11]  F. Disalvo,et al.  Thermoelectric cooling and power generation , 1999, Science.

[12]  L. Gu,et al.  Electrically Induced Ferromagnetism at Room Temperature in Cobalt-Doped Titanium Dioxide , 2011, Science.

[13]  Masashi Kawasaki,et al.  Electric-field-induced superconductivity in an insulator. , 2008, Nature materials.

[14]  Gilles Horowitz,et al.  A Water‐Gate Organic Field‐Effect Transistor , 2010, Advanced materials.

[15]  T. Okuda,et al.  Large thermoelectric response of metallic perovskites: Sr 1 − x La x TiO 3 ( 0 x 0 . 1 ) , 2001 .

[16]  G. J. Snyder,et al.  Complex thermoelectric materials. , 2008, Nature materials.

[17]  George S. Nolas,et al.  Semiconducting Ge clathrates: Promising candidates for thermoelectric applications , 1998 .

[18]  H. Koinuma,et al.  Atomic Control of the SrTiO3 Crystal Surface , 1994, Science.