Terahertz and Infrared Spectroscopy of Gated Large-Area Graphene

TL;DR

This study demonstrates the ability to modulate terahertz and infrared transmission in large-area graphene devices through electrical gating and thermal annealing, providing insights into Dirac fermion behavior and potential optoelectronic applications.

Contribution

It introduces a large-area graphene device with gating capabilities and characterizes its terahertz and infrared response over a wide frequency range, revealing tunable conductivity and absorption features.

Findings

Effective modulation of Fermi energy via gating and annealing.

Observation of Drude-like intraband absorption changes.

Identification of the '2E_F onset' for interband absorption.

Abstract

We have fabricated a centimeter-size single-layer graphene device, with a gate electrode, which can modulate the transmission of terahertz and infrared waves. Using time-domain terahertz spectroscopy and Fourier-transform infrared spectroscopy in a wide frequency range (10-10000 cm^{-1}), we measured the dynamic conductivity change induced by electrical gating and thermal annealing. Both methods were able to effectively tune the Fermi energy, E_F, which in turn modified the Drude-like intraband absorption in the terahertz as well as the '2E_F onset' for interband absorption in the mid-infrared. These results not only provide fundamental insight into the electromagnetic response of Dirac fermions in graphene but also demonstrate the key functionalities of large-area graphene devices that are desired for components in terahertz and infrared optoelectronics.