Graphene wettability control: Texturing of the substrate and removal of airborne contaminants in the atmosphere of various gases

Experimental and theoretical studies on the wettability of graphene coating are carried out. Molecular dynamic modeling is used to structure water molecules on the surface of copper and graphene-copper, as well as to assess wettability. The instability of the properties of graphene coatings over time is one of the reasons that inhibit their widespread use as highly sensitive sensors. The adsorption of water vapor and airborne contaminations on the graphene surface leads to a change in the electrical properties of the coating. The influence of key parameters (copper recrystallization, copper oxidation due to graphene surface defects, wall textures and airborne contaminations) on the wettability of the graphene coating is investigated for the first time. It is shown that the predominant effect on the change in wettability is exerted by hydrocarbon impurities. Molecular dynamic modeling demonstrates that an insignificant local separation of copper, as well as an inhomogeneous graphene coating, increases the angle on the graphene coating from 25 to 30 degrees to 60-65 degrees. To remove the hydrocarbon layer, annealing is carried out in a wide temperature range, as well as in the atmosphere of argon and hydrogen. A comparison of various methods of removing impurities is carried out. After prolonged annealing, the contact angle of the drop decreases from 80 to 90 degrees to 55 degrees. (C) 2021 Elsevier B.V. All rights reserved.