Evidence of ionic film deposition from single-filament dielectric barrier discharges in Ar–HMDSO mixtures

Abstract

The short residence time of Ar–HMDSO (Ar–hexamethyldisiloxane) gas mixtures rapidly flowing across atmospheric-pressure, glow-type, single-filament dielectric barrier discharges is utilized to accomplish thin-film deposition via a purely ionic route. A comparison of thin-film volumes obtained from profilometry, on the one hand, and from the transferred charge, on the other hand, enables to evaluate the mass of the ions contributing to the film growth. For HMDSO fractions at the lower end of the studied range of molar fractions, 50 ppm, pentamethyldisiloxanyl cations (Me3SiOSiMe2+, PMDS+), generated from the monomer via Penning ionization by Ar(1s) species, are mainly responsible for film formation. For HMDSO fractions growing beyond 1,000 ppm, ionic oligomerization processes by reactions of PMDS+ with HMDSO molecules result in a 2.5-fold increase of the average deposited ion mass.