Mechanism for the Large Conductance Modulation in Electrolyte-gated Thin Gold Films

Abstract

Electrolyte gating using ionic liquid electrolytes has recently generated considerable interest as a method to achieve large carrier density modulations in a variety of materials. In noble metal thin films, electrolyte gating results in large changes in sheet resistance. The widely accepted mechanism for these changes is the formation of an electric double layer with a charged layer of ions in the liquid and accumulation or depletion of carriers in the thin film. We report here a different mechanism. In particular, we show using x-ray absorption near edge structure (XANES) that the previously reported large conductance modulation in gold films is due to reversible oxidation and reduction of the surface rather than the charging of an electric double layer. We show that the double layer capacitance accounts for less than 10\% of the observed change in transport properties. These results represent a significant step towards understanding the mechanisms involved in electrolyte gating.

References in corpus (4)

• Double layer in ionic liquids: Overscreening vs. crowding
• Electrolyte gate-controlled Kondo effect in SrTiO3
• Large conductance modulation of gold thin films by huge charge injection via electrochemical gating
• Electrostatic gating of metallic and insulating phases in SmNiO3 ultrathin films

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