Thin film deposition and surface modification with atmospheric pressure dielectric barrier discharges

Abstract

This paper focuses on some of the most debated issues concerning the utilization of atmospheric pressure dielectric barrier discharges (DBDs) in surface processing of materials such as, for instance, the existence of different discharge regimes (filamentary and homogeneous) and the influence on the discharge behaviour of feed gas additives and substrate properties (chemical composition, electrical characteristics, etc.). Crucial aspects of the DBD operation which highly differentiate this approach from the well established low pressure plasma technology will be discussed. An overview of the state of the art in atmospheric pressure thin film deposition from fluorocarbon- or organosilicon-containing DBDs will be also provided. In particular the possibility of tailoring the chemical composition of the coatings, the etching–deposition competition and the influence of feed gas contaminants (i.e. air and H 2O) in the deposition of fluoropolymers will be discussed. Recent results on the deposition of SiO xC yH z thin films from three different methyldisiloxanes (i.e. hexamethyldisiloxane, pentamethyldisiloxane and tetramethyldisiloxane) will allow to highlight the effect of the chemical structure of the organosilicon precursor and of the oxygen-to-methyldisiloxane feed ratio on the properties of the deposits. The results obtained through different diagnostic techniques of the plasma phase (i.e. optical emission spectroscopy and GC–MS analysis of the exhaust gas) and of the deposits (i.e. XPS, FT-IR, SEM, and WCA) allow to highlight interesting aspects of the fluorocarbon and organosilicon plasma chemistry at atmospheric pressure.