Chemical Vapor Deposition (CVD) is the most popular technique to synthesize thin films, among them graphene layers, thanks to its ease of setup, successful long-term use in industrial settings, and the potential to scale up fabrication. A variety of different CVD process approaches can be employed in this synthesis, according to the characteristics of the processing parameters (pressure, temperature, precursor nature, gas flow state, wall/substrate temperature, depositing time, and activation manner).
For instance, a cold-wall CVD approach or a Plasma-Enhanced CVD (PECVD) one can be used for graphene growth. In the first one, the substrate is directly heated to the desired growth temperature in an unheated reaction chamber. Whereas in the second, a high frequency voltage ignites plasma to low pressure gas forming the reactive species needed for graphene deposition and making possible a reduction in the growth temperature requirements. Catalytic metal substrates such as Cu, Pt and Ru are used to favour the graphene layer formation, giving place to uniform thickness single layer graphene films, thanks to the low solubility of C in those metals.
After the synthesis, the graphene layers must be transferred to the final substrate used for the fabrication of devices.
Functionalization of graphene-based materials is also a widely used technique, allowing the tunning of the chemico-physical surface properties and morphology of graphene nanosheets. Tailored graphene materials and composites can be realized by ad-hoc chemical methodologies and enable to target specific sorption capability with resulting new applications in environmental and biomedical fields.