Self-aligned local electrolyte gating of 2D materials with nanoscale resolution

摘要

In the effort to make 2D materials-based devices smaller, faster, and moreefficient, it is important to control charge carrier at lengths approaching thenanometer scale. Traditional gating techniques based on capacitive couplingthrough a gate dielectric cannot generate strong and uniform electric fields atthis scale due to divergence of the fields in dielectrics. This fielddivergence limits the gating strength, boundary sharpness, and pitch size ofperiodic structures, and restricts possible geometries of local gates (due towire packaging), precluding certain device concepts, such as plasmonics andtransformation optics based on metamaterials. Here we present a new gatingconcept based on a dielectric-free self-aligned electrolyte technique thatallows spatially modulating charges with nanometer resolution. We employ acombination of a solid-polymer electrolyte gate and an ion-impenetrablee-beam-defined resist mask to locally create excess charges on top of the gatedsurface. Electrostatic simulations indicate high carrier density variations of$\Delta n =10^{14}\text{cm}^{-2}$ across a length of 10 nm at the maskboundaries on the surface of a 2D conductor, resulting in a sharp depletionregion and a strong in-plane electric field of $6\times10^8 \text{Vm}^{-1}$across the so-created junction. We apply this technique to the 2D materialgraphene to demonstrate the creation of tunable p-n junctions foroptoelectronic applications. We also demonstrate the spatial versatility andself-aligned properties of this technique by introducing a novel graphenethermopile photodetector.