Unusually large enhancement of thermopower in an electric field induced two-dimensional electron gas

Abstract

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 μV/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|.

20 pages including 4 figures and Supporting Information, Advanced Materials (in press)

References in corpus (1)

• Field-induced water electrolysis switches an oxide semiconductor from an insulator to a metal

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