Nondestructive Characterization of the Structural Quality and Thickness of Large-Area Graphene on Various Substrates

We demonstrate an inspection technique, based on only one ellipsometric parameter, Psi of spectroscopic ellipsometry (SE), for the rapid, simultaneous identification of both the structural quality and thicknesses of large-area graphene films. The measured Psi spectra are strongly affected by changes in the out-of-plane absorption coefficients (alpha(TM)); they are also correlated to the ratio of the intensities of the D and G bands in Raman spectra of graphene films. In addition, the electronic transition state of graphene within the UV regime assists the characterization of the structural quality. We also demonstrated that the intensities and shifts of the signals in Psi spectra allow clear identification of the structural qualities and thicknesses, respectively, of graphene films. Moreover, this Psi-based method can be further applied to graphene films coated on various substrates. In addition, mapping of the values of Psi is a very convenient and useful means of rapidly characterizing both the structural quality and thickness of 2D materials at local areas. Therefore, this Psi-based characterization method has great potential for application in the mass production of devices based on large-area graphene.