Nanometer-Scale Lateral p–n Junctions in Graphene/α-RuCl₃ Heterostructures

Abstract

The ability to create nanometer-scale lateral p–n junctions is essential for the next generation of two-dimensional (2D) devices. Using the charge-transfer heterostructure graphene/α-RuCl 3 , we realize nanoscale lateral p–n junctions in the vicinity of graphene nanobubbles. Our multipronged experimental approach incorporates scanning tunneling microscopy (STM) and spectroscopy (STS) and scattering-type scanning near-field optical microscopy (s-SNOM) to simultaneously probe the electronic and optical responses of nanobubble p–n junctions. Our STM/STS results reveal that p–n junctions with a band offset of ∼0.6 eV can be achieved with widths of ∼3 nm, giving rise to electric fields of order 10 8 V/m. Concurrent s-SNOM measurements validate a point-scatterer formalism for modeling the interaction of surface plasmon polaritons (SPPs) with nanobubbles. Ab initio density functional theory (DFT) calculations corroborate our experimental data and reveal the dependence of charge transfer on layer separation. Our study provides experimental and conceptual foundations for generating p–n nanojunctions in 2D materials.

Ultralocalized Optoelectronic Properties of Nanobubbles in 2D Semiconductors

“…Recently, several 2D materials interfaces have shown the ability to realize large charge transfer at the interface. 42,43 Our results indicate that such interfacial engineering together with nanostructuring can be employed to create optical emitters with arbitrarily desired shapes at the nanoscale. Our work provides a clear route to achieving this in the future.…”

Visualizing In‐Plane Junctions in Nitrogen‐Doped Graphene

“…[5] Substrate engineering has been used to induce potential wells in graphene through variations of substrate surface reconstruction, [6] vacancy islands, [7] interfacial charge transfer in graphene/α-RuCl 3 heterostructures. [8] Controlled local doping has been achieved by combining STM tip manipulation with back gate electrode. [9,10] In these works, the doping was achieved by the interaction of pure graphene with the environment.…”

Ultrasharp Lateral p–n Junctions in Modulation-Doped Graphene

“…The positive shift of the CNP takes place rapidly over ∼7 nm. A recent work in which STM was used to map the charge density in a nanobubble in graphene on α-RuCl 3 , at room temperature, finds an even sharper interface across a p–n junction . We note that an instability in STS is observed at the step edge, where the tip–sample interaction may lead to a small delamination of the graphene with a decrease in the charge transfer …”

“…A recent work in which STM was used to map the charge density in a nanobubble in graphene on α-RuCl 3 , at room temperature, finds an even sharper interface across a p−n junction. 36 We note that an instability in STS is observed at the step edge, where the tip−sample interaction may lead to a small delamination of the graphene with a decrease in the charge transfer. 37 To understand both the lateral and vertical spatial distributions of the charge transfer due to the modulation- doping of graphene by α-RuCl 3 , we perform first-principles calculations of a monolayer-thick α-RuCl 3 ribbon on graphene, as shown in Figure 4a,b.…”