Huge field-effect surface charge injection and conductance modulation in metallic thin films by electrochemical gating

The field-effect technique, popular thanks to its application in common field-effect transistors, is here applied to metallic thin films by using as a dielectric a novel polymer electrolyte solution. The maximum injected surface charge, determined by a suitable modification of a classic method of electrochemistry called double-step chronocoulometry, reached more than 4 × 10^15 charges/cm^2. At room temperature, relative variations of resistance up to 8%, 1.9% and 1.6% were observed in the case of gold, silver and copper, respectively and, if the films are thick enough (>=25 nm), results can be nicely explained within a free-electron model with parallel resistive channels. The huge charge injections achieved make this particular field-effect technique very promising for a vast variety of materials such as unconventional superconductors, graphene and 2D-like materials.