Dual-gated graphene devices for near-field nano-imaging

TL;DR

This paper demonstrates two methods for integrating top-gates in graphene heterostructures to enable near-field nano-imaging, advancing the study of tunable plasmonic and electronic phenomena.

Contribution

It introduces and compares bilayer MoS₂ and monolayer graphene top-gates for nano-optics, facilitating detailed near-field investigations of correlated electronic phases.

Findings

Nano-infrared imaging performed on both structures.

Evaluation of strengths and weaknesses of each gating approach.

Facilitates future studies of plasmonic effects in graphene heterostructures.

Abstract

Graphene-based heterostructures display a variety of phenomena that are strongly tunable by electrostatic local gates. Monolayer graphene (MLG) exhibits tunable surface plasmon polaritons, as revealed by scanning nano-infrared experiments. In bilayer graphene (BLG), an electronic gap is induced by a perpendicular displacement field. Gapped BLG is predicted to display unusual effects such as plasmon amplification and domain wall plasmons with significantly larger lifetime than MLG. Furthermore, a variety of correlated electronic phases highly sensitive to displacement fields have been observed in twisted graphene structures. However, applying perpendicular displacement fields in nano-infrared experiments has only recently become possible (Ref. 1). In this work, we fully characterize two approaches to realizing nano-optics compatible top-gates: bilayer $\text{MoS}_2$ and MLG. We perform nano-infrared imaging on both types of structures and evaluate their strengths and weaknesses. Our work paves the way for comprehensive near-field experiments of correlated phenomena and plasmonic effects in graphene-based heterostructures.