Electric‐Field Control of the Metal‐Insulator Transition in Ultrathin NdNiO3 Films

Field-effect transistors (FETs) are ubiquitous in our everyday life. Applying the fi eld-effect technique to new materials can lead not only to a modulation of their conductivity, but also to electrostatically driven phase transitions. [ 1–3 ] This method is particularly appealing for complex oxides, which exhibit a wide range of functional properties including metal-insulator (MI) transitions, colossal magnetoresistance and highT c superconductivity, all very sensitive to the level of electronic doping. The electric fi eld-effect approach seems thus to be a natural tool to try controlling and modifying reversibly the ground states of these materials. However, the required changes in carrier densities, which typically exceed 10 14 cm − 2 , [ 1 , 4 ] are diffi cult to induce with standard dielectrics. Recently, electric double layer transistors (EDLT), in which an ionic liquid or an electrolyte is used as a gate dielectric, have been the subject of intense research and rapidly increasing interest owing to the considerable amount of charge which can be provided by this technique. [ 5–7 ]