  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.
