Optical response of large scale single layer graphene

We have measured optical transmission and reflection spectra of large scale graphene grown by chemical vapor deposition technique over the extensive frequency range from far-IR to uv (4 meV-6.2 eV). Large scale graphene exhibits an excitonic absorption peak in the uv-region (hω=4.6 eV) and the constant interband absorption with σ₁ (ω) = e²/4h in the IR-visible region, respectively. In the far-IR range, Drude peak is observed, and its strength ω _p,2d²indicates the induced carrier density N_2d=1.95× 10¹²cm ^-2. These results are highly consistent with the theoretical prediction/experimental results of the single layer graphene. It proves that, contrary to the doubts about its quality due to the chemical growth process, the sample has single layer optical response over the entire photon energy; therefore, it can be applied to large scale devices such as terahertz-IR detector, solar cell material, and visible uv-transparent conductor.