Increasing the adhesion of graphene on quartz through fluorination

Abstract

Graphene was the first 2D-material ever discovered, and its unique properties open up for many applications. Due to its high mechanical resistance and transparency, it has been investigated as a coating for optical devices such as windows or lenses. A particular focus has been as an anti-icing coating where graphene functionalized with fluorine atoms, so-called fluorinated graphene, has been demonstrated to inhibit ice formation. However, to function as a durable coating the adhesion between graphene and the underlying substrate must be strong. Up till now it has not been possible to deposit graphene/functionalized graphene on a transparent substrate, such as SiO₂, with strong adhesion, without an intermediate metal layer (that gradually makes it opaque). Through optical and electron microscopy observation of surfaces scratched with a sapphire tip, we show how a transparent, functionalized graphene coating with improved adhesion can be created through fluorination of graphene transferred onto a quartz substrate ($\alpha$-SiO₂). The fluorination leads to an increase in adhesion of approximately 3 times compared to unfluorinated graphene adhered to the same substrate. Comparing this with reported adhesion energies for graphene on SiO₂ gives an estimated adhesion energy between 0.03 J/m² and 9 J/m² for graphene fluorinated on SiO₂.