Optical contrast of single- and multi-layer graphene deposited on a gold   substrate
  We study the optical contrast for single and multilayer graphene deposited on a Au/SiO2/Si substrate. Our results prove that optical microscopy allows for easy and quick localization, identification and counting of graphene layers. Visibility depends on the thicknesses of the Au and SiO2 layers as well as the wavelength of the light used. We propose optimum parameters for the detection of graphene. 
Igor Wlasny, Pawel Dabrowski, Zbigniew Klusek
cond-mat.mes-hall