Room-temperature Tunable Fano Resonance by Chemical Doping in Few-layer Graphene Synthesized by Chemical Vapor Deposition

TL;DR

This study demonstrates room-temperature tunable Fano resonance in few-layer graphene via chemical doping, revealing strong electron-phonon interactions and Fano line shape variations dependent on doping levels.

Contribution

It introduces a method to control Fano resonance in graphene at room temperature through chemical doping, highlighting the tunability of electron-phonon interactions.

Findings

Fano resonance observed at room temperature in few-layer graphene.

Fano line shape varies from anti-resonance to phonon-dominated with doping.

Resonance strength peaks near the Dirac point.

Abstract

A Fano-like phonon resonance is observed in few-layer (~3) graphene at room temperature using infrared Fourier transform spectroscopy. This Fano resonance is the manifestation of a strong electron-phonon interaction between the discrete in-plane lattice vibrational mode and continuum electronic excitations in graphene. By employing ammonia chemical doping, we have obtained different Fano line shapes ranging from anti-resonance in hole-doped graphene to phonon-dominated in n-type graphene. The Fano resonance shows the strongest interference feature when the Fermi level is located near the Dirac point. The charged phonon exhibits much-enhanced oscillator strength and experiences a continuous red shift in frequency as electron density increases. It is suggested that the phonon couples to different electronic transitions as Fermi level is tuned by chemical doping.