Effect of Plasma Exposure on the Chemistry and Morphology of Aerosol-Assisted, Plasma-Deposited Coatings

This study reports on the effect on the morphology and chemistry of atmospheric pressure plasma deposited nm-thick coatings (21 +/- 3 nm) as the level of exposure to the plasma is systematically altered. Coatings were deposited by directly injecting hexamethyldisiloxane, polydimethylsiloxane or tetramethyldisiloxane liquid precursors through a nebulizer into a helium/oxygen atmospheric pressure plasma. An increase in the level of the precursor was found to be associated with a decrease in the concentration of methyl functional groups in the coating and an increase of Si-O crosslinking, as demonstrated using surface energy and XPS analysis. This resulted in an increase in the coating refractive index, and in a reduction of the number of surface particulates, as well as of surface roughness.