Making graphene visible

TLDR: In this paper, the authors studied the visibility of graphene and showed that it depends strongly on both thickness of silicon dioxide and light wavelength, and they used a Fresnel-law-based model to quantitatively describe the experimental data without any fitting parameters.

Abstract: 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 silicon wafers with a certain thickness of silicon dioxide. We study graphene's visibility and show that it depends strongly on both thickness of silicon dioxide and light wavelength. We have found that by using monochromatic illumination, graphene can be isolated for any silicon dioxide thickness, albeit 300 nm (the current standard) and, especially, approx. 100 nm are most suitable for its visual detection. By using a Fresnel-law-based model, we quantitatively describe the experimental data without any fitting parameters.