Ellipsometric measurements were made with a Gaertner model L2W26D ellipsometer. An analyzing wavelength of 632 nm was used, because GO absorbs minimally at this wavelength. The incident angle was 70° and the polarizer was set at 45°. Ellipsometric parameters were measured following each GO or PAH adsorption step. Si substrates were dried in an Ar stream before each measurement. The film thickness of the GO/PAH multilayers was calculated using the Si refractive indices, ns ) 3.875 and ks ) -0.018, determined from a blank sample. The refractive index of GO/PAH films was estimated as nf ) 1.540, kf ) 0.