Molecular Doping on Epitaxial Graphene by Gaseous Surface Adsorbents: Influence of Interband Scattering

Abstract

We investigate molecular adsorption doping by electron withdrawing NO2 and electron donating NH3 on epitaxial graphene grown on C-face 6H-SiC substrates. We reconcile models describing the conductivity of graphene at low and high frequencies in the relaxation time approximation. These equations are applied to develop theoretical model for adsorption of NO2 and NH3 molecules on an epitaxial graphene surface probed by infrared reflectance, a non-destructive technique for transport studies in graphene. We separate the intraband and interband scattering contributions to the electronic transport under gas adsorption. We find that only by including a significant interband (intraband) contribution can measured reflectance be fit accurately at low (high) frequency regime. Interband relaxation times as short as ~0.1 fs are obtained under gas adsorption, much shorter than previously assumed (~100 fs), leading to a breaking of the usual universal conductivity observed in purer samples. This method can also calculate percentage charge transfer by NO2 to graphene (1~2 %) and NH3 to graphene (0.01~0.1 %). Finally, this transport behavior indicate that, under gas adsorption, the influence of interband scattering cannot be neglected, even at DC

Keywords

• Graphene
• Molecular adsorption doping
• Interband Scattering
• Gas adsorption