New perspectives of atmospheric pressure dielectric barrier discharges for the deposition of thin films: From uncontrolled amorphous plasma-polymer layers to chemically patterned and crystalline (in)organic coatings

Abstract

For more than a century, atmospheric pressure dielectric barrier discharges (DBDs) have been utilized in industries for gas conversion and surface treatment. However, the application of DBDs for coating deposition remained limited due to challenges in controlling film quality. At atmospheric pressure, the extremely short mean free path results in species with very low energies, often causing random processes due to moving filaments.

In this paper, we show that, today, DBD technology can produce chemically well-controlled and tunable thin films using organic or inorganic precursors. Atmospheric pressure dielectric barrier discharges are either used to deposit organic or crystalline inorganic coatings, with or without chemical patterning, thanks to the immobilization of plasma filaments, evidencing the versatility of this new approach. The influence of the plasma parameters and the precursor chemistry on the composition of plasma-polymerized organic coatings is shown. More specifically, the protective effect of double bonds in the precursor structure on the chemical functionalities in the final coatings is evidenced, along with the impact on the deposition rate. In parallel, the nature of the plasma gas is shown to influence the final chemistry of the coatings, and the deposition rate. The effect of the plasma frequency on the crystal size of vanadium coatings is also shown and explained. Immobilizing filaments enables spatial chemically differentiation between organic and inorganic coatings. The local chemistry can be tuned by changing the gas gap, the monomer flow and the oxygen content (for inorganic coatings).