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 n2D as high as 3.5×10^15  e/cm^2 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 n2D—as expected within a free-electron model—if the film is thick enough (≥25  nm); 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.