Thin films containing carboxylic acid groups are deposited from mixtures of helium, acrylic acid, and ethylene using an atmospheric pressure cold plasma jet in dielectric barrier discharge (DBD) configuration. The influence of the feed gas composition on the properties of the deposits is investigated. As assessed by X-ray photoelectron spectroscopy (XPS), the oxygen atomic concentration of the coatings as well as the percentage of the XPS C1s component ascribed to carboxylic groups (i.e., COOH and COOR moieties) increase with the acrylic acid concentration in the feed gas. On the other hand, ethylene addition enhances the deposition rate, reduces the carboxylic groups content of the coatings, and significantly improves their chemical and morphological stability upon immersion in water for 72 h. The surface concentration of COOH groups before and after immersion in water is determined by chemical derivatization in conjunction with XPS

Surface processing of materials by atmospheric pressure dielectric barrier discharges (DBDs) has experienced significant growth in recent years. Considerable research efforts have been directed for instance to develop a large variety of processes which exploit different DBD electrode geometries for the direct and remote deposition of thin films from precursors in gas, vapor and aerosol form. This article briefly reviews our recent progress in thin film deposition by DBDs with particular focus on process optimization. The following examples are provided: (i) the plasmaenhanced chemical vapor deposition of thin films on an open-cell foam accomplished by igniting the DBD throughout the entire three-dimensional (3D) porous structure of the substrate, (ii) the preparation of hybrid organic/inorganic nanocomposite coatings using an aerosol-assisted process, (iii) the DBD jet deposition of coatings containing carboxylic acid groups and the improvement of their chemical and morphological stability upon immersion in water

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In the present study, we investigate different surface pretreatments and their influence on a subsequent surface metallization. A direct liquid injection metalorganic CVD (DLI-MOCVD) process is presented for the low temperature metallization of composites, ultimately aiming at the surface functionalization of 3D parts. The process involves the organometallic precursor Cu(I) hexafluoroacetylacetonate 2-methyl-1-hexene-3-yne (hfac)Cu(MHY). We determine chemical kinetics of the global deposition reaction and show the improvement of the adhesion of the Cu films by applying surface pretreatments that etch and/or activate the surface before deposition. To this purpose, gas phase and wet chemical processes are used. Gas phase pretreatments consist either in the use of a remote microwave plasma, an in situ UV oxidation, or in the deposition of acrylic acid/ethylene plasma buffer layer by using an atmospheric pressure cold plasma jet. The liquid phase pretreatment is based on a commercial series of solutions that includes swelling, oxidation, and neutralization steps. The adhesive strength of the Cu films on poly-epoxy and on carbon fiber/poly-epoxy composite surfaces is specifically investigated by scratch and cross-cut testing, and is correlated with topographical, chemical, and energetic characteristics of the surfaces prior deposition, investigated by interferometry, X-ray photoelectron spectroscopy and wettability measurements through the sessile drop method. Pretreatments result in surface functionalization and topographical changes which significantly increase the surface energy and improve the wettability. In some cases the induced modification of the microstructure of the Cu films is found to be beneficial to the electrical resistivity.

Iron oxide thin films for photoelectrochemical (PEC) water splitting were deposited by radiofrequency sputtering of an iron target in argon/oxygen plasma mixtures, followed by thermal annealing. The chemical composition and structure of deposited film can be tuned by controlling the gas feed composition and the annealing temperature. The thermal treatment extensively improves the PEC water splitting performances of the films deposited at the lowest O2 percentages (0–1%), allowing to obtain photocurrent densities up to 1.20 mA/cm2 at 1.23 VRHE. Increasing the oxygen percentage in the plasma feed allows the direct growth of photoactive films; the best result is found for the hematite film produced at 50% O2, characterized by a photocurrent density of 0.21 at 1.23 VRHE.