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

Water is composed of two strong electrochemically active agents, H(+) and OH(-) ions, but has not been used as an active electronic material in oxide semiconductors. In this study, we demonstrate that water-infiltrated nanoporous glass electrically switches an oxide semiconductor from insulator to metal. We fabricated a field-effect transistor structure on an oxide semiconductor, SrTiO(3), using water-infiltrated nanoporous glass-amorphous 12CaO·7Al(2)O(3)-as the gate insulator. Positive gate voltage, electron accumulation, water electrolysis and electrochemical reduction occur successively on the SrTiO(3) surface at room temperature. This leads to the formation of a thin (~3 nm) metal layer with an extremely high electron concentration (10(15)-10(16) cm(-2)), which exhibits exotic thermoelectric behaviour. The electron activity of water as it infiltrates nanoporous glass may find many useful applications in electronics or in energy storage.