Molecular Gas Adsorption Induced Carrier Transport Studies of Epitaxial Graphene using IR Reflection Spectroscopy

TL;DR

This study explores how molecular adsorption of NO2 and NH3 affects carrier transport in epitaxial graphene by analyzing IR reflection spectra, revealing changes in carrier concentration and scattering mechanisms.

Contribution

It introduces a method to correlate IR reflection spectra with electronic transport properties of graphene under gas adsorption, separating intraband and interband scattering effects.

Findings

Adsorption of NO2 and NH3 alters carrier concentration in graphene.

IR reflection spectra can be used to quantify scattering changes due to gas adsorption.

Interband scattering significantly impacts electronic transport even at DC.

Abstract

We investigate molecular adsorption doping by electron withdrawing NO2 and electron donating NH3 on epitaxial graphene grown on C-face SiC substrates. Amperometric measurements show conductance changes upon introduction of molecular adsorbents on epitaxial graphene. Conductance changes are a trade-off between carrier concentration and scattering, and manifest at direct current and optical frequencies. We therefore investigate changes in the infrared (IR) reflection spectra to correlate these two frequency domains, as reflectance changes are due to a change of epitaxial graphene (EG) surface conductance. We match theory with experimental IR data and extract changes in carrier concentration and scattering due to gas adsorption. Finally, we separate the intraband and interband scattering contributions to the electronic transport under gas adsorption. The results indicate that, under gas adsorption, the influence of interband scattering cannot be neglected, even at DC.