The magnitude of the optical sheet resistance of single layer graphene is universal, and equal to e2/4ħ. As the optical frequency decreases, the conductivity decreases. However, at some frequency in the THz range, the conductivity increases again, eventually reaching the dc value, where the magnitude of the dc sheet resistance is continuously variable between of order e2/h and 100 e2/h. Thus, the THz range is predicted to be a non-trivial region of the spectrum of the fundamental properties of graphene, and may have interesting technological applications. We currently published the first measurements of the absolute value of multilayer and single layer sheet conductivity and transparency from DC to 1 THz, and establish a firm foundation for future THz applications of graphene.
Source: Nima Rouhi, Yung Yu Wang, Peter Burke.
“Ultrahigh conductivity of large area suspended few layer graphene films”
Applied Physics Letters, 2012, 101, 263101, DOI: 10.1063/1.4772797