Chemical and Physical Effects of the Carrier Gas on the Atmospheric Pressure PECVD of Fluorinated Precursors

Abstract

International audienceThe atmospheric pressure PECVD deposition and texturization of hydrophobic coatings using liquid fluorinated C6F12 and C6F14 precursors are investigated. The effect of the carrier gas (argon and helium) is discussed in terms of the behavior of the gas phase and of the characteristics of the deposited film. Mass spectrom-etry measurements indicate that the fragmentation is higher with argon while helium reacts very easily with oxygen impurities leading to the formation of CxFyOz compounds. These observations are consistent with the chemical composition of the films determined by XPS and the variation in the deposition rate. Moreover, the streamers present in the argon discharge affect the morphology of the surface by increasing the roughness, which leads to the increase in the hydrophobicity of the coatings

Challenges in the characterization of plasma polymers using XPS

“…Characteristic values of the XPS C 1s spectra of polyvinyl alcohol (PVA) and polyethylene (PE) calculated using the OPLS all atom force field model. FWHM for CH 2 (C 9/11 (H 2 )) or CHOH (C 10 (see table 5) [91]. Although conscious of a small oxygen uptake in the coatings generated from helium discharges, the authors did not consider oxygenated carbons in the core-level C 1s lineshape fitting, for ease of interpretation.…”

“…Surface composition of pp-C x F y films as a function of the precursor and the carrier gas. Data from [91].…”

“…Data from[90,91].Alexander et al also reported larger FWHMs for plasma-polymerized acrylic acid coatings (1.4-1.5 eV) than for their conventional counterparts (1.1-1.2 eV), using a monochromated aluminium source[92]. Merche came to the same conclusion for plasma-polymerized polystyrene, which exhibited a FWHM of the C 1s peak of 1.6 eV compared to 1.3-1.4 eV for conventional polystyrene[93].As shown in Section 1, plasma polymers potentially consist of more random structures and may contain chains of different lengths, which generates a different global electronic structure.…”

“…of the conventional polymer is 1.6-1.7 eV, whereas the one of the plasma polymer is 1.9-2.0 eV[90,91].…”

Thin film deposition at atmospheric pressure using dielectric barrier discharges: Advances on three-dimensional porous substrates and functional coatings

“…[1][2][3][4][5] Intense research efforts have been made to adapt the classical plasma-enhanced chemical vapor deposition (PECVD) processes to the specific features of DBD operation, as for instance the existence of different discharge regimes, the use of high flow rates of a dilution gas in combination with low concentrations of thin film precursors, the limitations imposed by the narrow gas gaps as well as the fluid dynamic issues associated to the feed mixture injection and discharge cell assembly. 1,2,[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Additionally, innovative deposition strategies have been developed, such as various aerosol-assisted processes [21][22][23][24] recently proposed for instance for the preparation of hybrid multicomponent coatings. [25][26][27][28][29] It has been demonstrated that DBD-based processes can afford the preparation of a wide range of coatings, spanning from the high quality dense inorganic layers (e.g., silica-like moisture barrier films 9,30) and hydrogenated silicon nitride layers for photovoltaics 31) ) obtained by diffuse DBDs, to the polymeric films characterized by superior retention of the monomer structure recently deposited using nanosecond pulsed DBDs.…”