Large conductance modulation of gold thin films by huge charge injection via electrochemical gating

By using an electrochemical gating technique with a new combination of polymer and electrolyte, we were able to inject surface charge densities n 2D as high as 3.5×1015e/cm2 in gold films and to observe large relative variations in the film resistance, ΔR/R ′, up to 10% at low temperature. ΔR/R ′ is a linear function of n 2D-as expected within a free-electron model-if the film is thick enough (25nm); otherwise, a tendency to saturation due to size effects is observed. The application of this technique to 2D materials might allow extending the field-effect experiments to a range of charge doping where large conductance modulations and, in some cases, even the occurrence of superconductivity are expected. © 2012 American Physical Society.