Tailored plasmons in pentacene/graphene heterostructures with interlayer electron transfer

TL;DR

This study investigates how the addition of pentacene layers affects surface plasmons in graphene, revealing a nonlinear wavelength change driven by interlayer electron transfer, and introduces a new way to tailor graphene plasmon properties.

Contribution

It demonstrates the influence of molecular layer thickness on graphene plasmons and attributes this to interlayer electron tunneling, advancing nano-optical control in vdW heterostructures.

Findings

Plasmon wavelength decreases nonlinearly with pentacene thickness.

Interlayer electron transfer significantly alters plasmon behavior.

Provides a new method to tailor graphene plasmons via molecular layering.

Abstract

Van der Waals (vdW) heterostructures, which are produced by the precise assemblies of varieties of two-dimensional (2D) materials, have demonstrated many novel properties and functionalities. Here we report a nano-plasmonic study of vdW heterostructures that were produced by depositing ordered molecular layers of pentacene on top of graphene. We find through nano-infrared (IR) imaging that surface plasmons formed due to the collective oscillations of Dirac fermions in graphene are highly sensitive to the adjacent pentacene layers. In particular, the plasmon wavelength declines systematically but nonlinearly with increasing pentacene thickness. Further analysis and density functional theory (DFT) calculations indicate that the observed peculiar thickness dependence is mainly due to the tunneling-type electron transfer from pentacene to graphene. Our work unveils a new method for tailoring graphene plasmons and deepens our understanding of the intriguing nano-optical phenomena due to interlayer couplings in novel vdW heterostructures.