The constriction of the positive column of a glow discharge in argon was studied both experimentally and theoretically. In experiments the direct current discharge was maintained in a cylindrical glass tube of 3 cm internal diameter and 75 cm length. The voltage–current U(I) characteristics of the discharge were measured at a gas pressure P from 1 to 120 Torr in a wide range of discharge currents. At P > 20 Torr the measured U(I) characteristics display the classical hysteresis effect: the transition from the diffuse to the contracted discharge form (with increasing current) occurs at a current higher than that for reverse transition (with decreasing current). It was also found that in some cases the so-called partially contracted form of the discharge is realized, when the diffuse and contracted forms coexist in the discharge tube.To calculate the plasma parameters under experimental conditions a 1D axial-symmetric discharge model for pure argon was developed. The details of the model are described and the results of simulations are presented. In particular, the electric field strength E in the positive column was calculated as a function of the discharge current. Theoretical E(I) characteristics are compared with those derived from the experiment. For the first time, the detailed kinetic model without the usage of fit parameters predicts the hysteresis effect in pure Ar with parameters of diffuse and constricted forms of the discharge in good agreement with the experiment.

This work reports on the main competing processes and their contribution to the properties of SiO2 layers on polymers in large area AP‐PE‐CVD from ArN2O2‐HMDSO mixtures. The detailed space resolved surface analysis on the statically deposited films showed smooth SiOx films in the vicinity of the gas injection, as deposited by HMDSO radicals. At the gas effluent, due to HMDSO depletion, non‐depositing species interact with the polymer and induce rough deposits with high carbon content. The competition of plasma–polymer surface interaction with HMDSO radicals deposition, is further confirmed from the analysis of films grown on polymers with a “protecting” layer and with reverse gas flow direction. Under web roll conditions, HMDSO radicals deposition is dominant, resulting in high quality SiOx layers along the whole electrode length.

Pathways of formation and temporal evolution of the diffuse dielectric barrier discharge at atmospheric pressure were experimentally studied in this work by means of optical (fast imaging camera) and electrical diagnostics. The chosen model system is relevant for applications of plasma-enhanced chemical vapor deposition of thin silica-like film on the polymeric substrate, from cost-efficient gas mixtures of Ar/N 2 /O 2 /hexamethyldisiloxane. It was found that the discharge can gradually experience the phases of homogeneous low current Townsend-like mode, local Townsend to glow transition and expanding high current density (∼0.7 A cm −2 ) glow-like mode. While the glow-like current spot occupies momentarily only a small part of the electrode area, its expanding behavior provides uniform treatment of the whole substrate surface. Alternatively, it was observed that a visually uniform discharge can be formed by the numerous microdischarges overlapping over the large electrode area.

The diffuse dielectric barrier discharge in atmospheric pressure air was applied for the thin film deposition on polymeric web in industrially relevant roll-to-roll configuration. The silica-like film deposition was performed using the admixture of hexamethyldisiloxane precursor to air flow. Fast discharge imaging at 2 μs exposure time confirms plasma uniformity in a single current pulse time scale. Morphology and composition analyses indicate that the process results in ultrasmooth films (roughness comparable to initial substrate roughness) and shows the possibility to synthesize carbon-free layers.

Front Cover: An atmospheric pressure diffuse dielectric barrier discharge between cylindrical rotary electrodes was applied for deposition of silica‐like moisture barrier films on polymer foil. The discharge was operated in N2/O2/Ar gas mixture with the addition of tetraethyl orthosilicate. It is shown that high quality permeation barrier films can be deposited by atmospheric pressure roll‐to‐roll process. Further details can be found in the article by Sergey A. Starostin et. al. http://doi.wiley.com/10.1002/ppap.201400194.

SiO2‐like layers deposited by means of the developed atmospheric pressure glow‐like DBD assisted CVD technology exhibit remarkable film properties, reported for the first time. The films synthesized in a roll‐to‐roll mode on polymeric webs, are as smooth as the substrate, irrespectively of the precursors (TEOS or HMDSO) and reactive gases (N2 or air) employed. Detailed AFM investigation on film morphology, surface roughness and auto correlation length (ξ) show that they are negligibly influenced with thickness and are similar to that of the polymeric substrate, indicating the self‐similar growth of the SiO2‐like layers in AP‐PECVD. The films are uniform with no defects or particle being incorporated during the deposition process. The produced single layers on polymeric substrate show excellent gas barrier performances towards O2 and H2O permeation (OTR: <5 × 10−3 cm3·m−2·day−1 and WVTR: <5 × 10−3 g·m−2·day−1).

An atmospheric pressure dielectric barrier discharge (DBD) was applied for the deposition of silica-like moisture barrier films on polyethylene 2,6 naphthalate foil. The diffuse plasma was sustained between two cylindrical drum electrodes in N 2 /O 2 /Ar gas flow with the addition of tetraethyl orthosilicate. The chemical composition, morphology and water vapour transmission rate of the moisture permeation barrier layers were studied as a function of the dynamic deposition rate and substrate temperature. It was demonstrated that dense silica-like layers of 100 nm thick with a good permeation barrier of �1.8 � 10À 3 g � m À 2 � day (at 40 8C, 90% RH), corresponding to three orders of magnitude barrier improvement with respect to the pristine polymer, can be deposited in an atmospheric pressure process.

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