Terahertz imaging and spectroscopy of large-area single-layer graphene

TL;DR

This study employs terahertz imaging and spectroscopy to analyze a large-area single-layer graphene film, enabling non-contact measurement of its carrier dynamics and sheet conductivity with high spatial resolution.

Contribution

It demonstrates broadband THz techniques for mapping and characterizing large-area graphene without electrodes, revealing spatial variations in conductivity.

Findings

Sheet conductivity varies from 1.7x10^-3 to 2.4x10^-3 {\

THz imaging maps carrier dynamics with sub-mm resolution.

Spectroscopy shows flat spectral response dominated by intraband transitions.

Abstract

We demonstrate terahertz (THz) imaging and spectroscopy of a 15x15-mm^2 single-layer graphene film on Si using broadband THz pulses. The THz images clearly map out the THz carrier dynamics of the graphene-on-Si sample, allowing us to measure sheet conductivity with sub-mm resolution without fabricating electrodes. The THz carrier dynamics are dominated by intraband transitions and the THz-induced electron motion is characterized by a flat spectral response. A theoretical analysis based on the Fresnel coefficients for a metallic thin film shows that the local sheet conductivity varies across the sample from {\sigma}s = 1.7x10^-3 to 2.4x10^-3 {\Omega}^-1 (sheet resistance, {\rho}s = 420 - 590 {\Omega}/sq).