Preparation of Water-Repellent Monomolecular Films by CF₄ Plasma Treatment on Hydrocarbon Monolayers

Abstract

Hydrocarbon monomolecular films were prepared on a glass slide with a chemical adsorption technique. Water-repellent fluorocarbon monomolecular films were prepared by CF₄ plasma treatment on the chemically adsorbed hydrocarbon monomolecular films. However, the monomolecular films were usually removed by sputtering when the CF₄ plasma was treated, because CF₄ plasma contains ions of the fluorocarbon fragments, not only its radicals. Therefore, fluorocarbon ions were removed from the plasma by mesh connected to the earth, and then only fluorocarbon radicals were used for treatment in order to prevent the monomolecular film from being removed. Fourier-transform infrared reflection absorption spectroscopy (FTIR-RAS) revealed that the hydrocarbon groups or hydrogens of the hydrocarbon monomolecular film were substituted with fluorocarbon or a fluorocarbon radical. In addition, the water drop contact angle of the film slightly increased by the treatment. It was demonstrated that water-repellent monomolecular films can be prepared by CF₄ plasma treatment on hydrocarbon monolayers. Thus, the plasma treatment technique may be useful into preparing the highly durable fluorinated monomolecular films with the cross linkage inter adsorbed molecules in the monolayer films.