Phonon-mediated mid-infrared photoresponse of graphene

TL;DR

This study investigates how graphene's photoresponse in the mid-infrared range is influenced by substrate phonons, revealing mechanisms that could enhance graphene-based thermal sensors.

Contribution

The paper provides a spectrally resolved analysis of mid-infrared photoresponse in graphene, highlighting phonon-related enhancement mechanisms on polar substrates.

Findings

Photoresponse is enhanced by substrate phonon excitation.

Different photocurrent generation mechanisms are identified.

Broad frequency range (1000-1600 cm$^{-1}$) analysis conducted.

Abstract

The photoresponse of graphene at mid-infrared frequencies is of high technological interest and is governed by fundamentally different underlying physics than the photoresponse at visible frequencies, as the energy of the photons and substrate phonons involved have comparable energies. Here we perform a spectrally resolved study of the graphene photoresponse for mid-infrared light by measuring spatially resolved photocurrent over a broad frequency range (1000-1600 cm$^{-1}$). We unveil the different mechanisms that give rise to photocurrent generation in graphene on a polar substrate. In particular, we find an enhancement of the photoresponse when the light excites bulk or surface phonons of the SiO$_2$ substrate. This work paves the way for the development of graphene-based mid-infrared thermal sensing technology.