Making graphene visible
Microfabrication of graphene devices used in many experimental studies currently relies on the fact that graphene crystallites can be visualized using optical microscopy if prepared on top of Si wafers with a certain thickness of SiO 2 . The authors study graphene's visibility and show that it depends strongly on both thickness of SiO 2 and light wavelength. They have found that by using monochromatic illumination, graphene can be isolated for any SiO 2 thickness, albeit 300 nm ͑the current standard͒ and, especially, Ϸ100 nm are most suitable for its visual detection. By using a Fresnel-law-based model, they quantitatively describe the experimental data.