Etude de l’effet de la composition d’une couche mince et de ses conditions d’élaboration par plasma froid à partir de vapeurs organosiliciées sur les propriétés de surface d’un film polymérique

Abstract

Plasma polymerization of hexamethyldisiloxane (PPHMDSO) was used to deposit SiOxCyHz thin films on silicon and polyimide substrates, using low-frequency plasma and microwave plasma discharge at low pressure. The effects of plasma chamber pressure, oxygen rate in Ar/O2 mixture, treatment time and post-treatment on the films characteristics were studied. The thickness, surface properties and chemical structure of the deposited thin films were analyzed using profilo-meter measurements, scanning electron microscopy (SEM), static contact angle and infrared spectroscopy (FTIR and FTIR-ATR). At low frequencies and for certain deposition parameters, nano-powders of different concentrations and sizes were observed on the deposited thin films surface. The FTIR analysis revealed that the chemical formula of the deposited layers is close to SiOxCyHz one, with more organic character when chamber pressure and/or deposition time were increased. Water contact angle measurements show that the increase in the deposition pressure and deposition time leads to the growth on the polyimide and silicon substrates of thin layers with super-hydrophobic surface due to the increase in the concentration of the nano-powders on the treated surfaces. Plasmas created in HMDSO vapours using a microwave frequency plasma in ECR reactor leads to the deposition of similar PPHMDSO thin layer on polyimide and silicon surfaces. A post-treatment of these coating layers using a microwave plasma created in Ar/O2 mixtures shows that the increase of oxygen rate in this mixture and the increase in the post-treatment time induces a significant decrease of the contact angle because of a decrease in the layers roughness (revealed by AFM characterization) and mainly, because of a more surface oxidation of the thin layers (revealed by FTIR analyzes).