Chemical and Physical Effects of the Carrier Gas on the Atmospheric Pressure PECVD of Fluorinated Precursors

The atmospheric pressure PECVD deposition and texturization of hydrophobic coatings using liquid fluorinated C₆F₁₂ and C₆F₁₄ precursors are investigated. The effect of the carrier gas (argon and helium) is discussed in terms of the behavior of the gas phase and of the characteristics of the deposited film. Mass spectrometry measurements indicate that the fragmentation is higher with argon while helium reacts very easily with oxygen impurities leading to the formation of C_xF_yO_z compounds. These observations are consistent with the chemical composition of the films determined by XPS and the variation in the deposition rate. Moreover, the streamers present in the argon discharge affect the morphology of the surface by increasing the roughness, which leads to the increase in the hydrophobicity of the coatings.