Low-Temperature Plasma Oxidation of Aluminum by Ar-O2 Mixtures in a Dielectric-Barrier Discharge Reactor

Abstract Room-temperature growth of oxide layers on aluminum in highly diluted mixtures oxygen with argon (O 2 molar fractions 20 ppm ≤ $$x_{O_2}$$ x O 2 500 ppm, partial pressures Pa $$p_{O_2}$$ p 50 Pa) flowing through a dielectric-barrier discharge (DBD) reactor is studied, including oxidation the pre- and post-discharge regions (PrD, PoD) adjacent to main DBD. Three different mechanisms plasma-enhanced were found prevail, depending location sample: (1) In close PrD region, up 1 cm upstream from discharge, accelerated Al O 3 due irradiation sample surface by energetic (9.8 eV) excimer radiation presence . (2) remote PoD, few downstream DBD, can largely be attributed atoms, number densities typically between 5 × 10 14 −3 Here, analysis terms Cabrera–Mott (CM) theory results CM potentials − 1.5 2.1 V. (3) DBD itself both atoms VUV photons generally play an important role but, under special conditions, additional mode identified, characterized much larger limiting thickness: While, general, and/or virtually stops at thicknesses X 6 nm, thicker films achieved region growing length zone. Tentatively, we attribute this observation negative ions m (1 3) accumulating gas while passing reactor. Any direct electrical effects process probably neglected.