A glow like atmospheric pressure dielectric barrier discharge in a roll‐to‐roll setup was used to synthesize 90 nm silica‐like bilayer encapsulation films composed of a 30 nm dense “barrier layer” and a comparatively less dense 60 nm “buffer layer” onto a polyethylene 2,6 naphthalate substrate by means of plasma enhanced chemical vapor deposition. Tetraethyl orthosilicate was used as the precursor gas, together with a mixture of nitrogen, oxygen, and argon. The microstructure, chemical composition, morphology, and permeation properties of the films were studied as a function of the specific energy delivered per precursor molecule, and oxygen concentration in the gas mixture, during the deposition of the barrier layer. The presence of the buffer layer within the bilayer architecture critically enhanced the encapsulation performance of the bilayer films, and this in conjunction with increasing the specific energy delivered per precursor molecule during the barrier layer deposition to a value of 20 keV, enabled an effective water vapor transmission rate as low as 6.9 × 10−4 g m−2 d−1 (at 40 °C, 90% relative humidity (RH)) to be achieved. Furthermore, the bilayer film structure has given rise to a remarkable 50% reduction in deposition energy consumption per barrier area with respect to single layer silica‐like films of equivalent encapsulation performance and thickness.

Abstract. Industrially and commercially relevant roll-to-roll atmospheric pressure-plasma enhanced chemical vapour deposition was used to synthesize smooth, 80 nm silica-like bilayer thin films comprising a dense 'barrier layer' and comparatively porous 'buffer layer' onto a flexible polyethylene 2,6 naphthalate substrate. For both layers, tetraethyl orthosilicate was used as the precursor gas, together with a mixture of nitrogen, oxygen and argon. The bilayer films demonstrated exceptionally low effective water vapour transmission rates in the region of 6.1×10 -4 g m -2 day -1 (at 40°C, 90% relative humidity), thus capable of protecting flexible photovoltaics and thin film transistors from degradation caused by oxygen and water. The presence of the buffer layer within the bilayer architecture was mandatory in order to achieve the excellent encapsulation performance. Atomic force microscopy in addition to solvent permeation measurements, confirmed that the buffer layer prevented the formation of performance-limiting defects in the bilayer thin films, which likely occur as a result of excessive plasma-surface interactions during the deposition process. It emerged that the primary function of the buffer layer was therefore to act as a protective coating for the flexible polymer substrate material.

Amorphous single layered silica films deposited using industrially scalable roll-to-roll atmospheric pressure-plasma enhanced chemical vapor deposition were evaluated in terms of structureperformance relationships. Polarised attenuated total reflectance-Fourier transform infrared absorption spectroscopy and heavy water exposure to induce hydrogen-deuterium exchange revealed it was possible to control the film porosity simply by varying the precursor flux and plasma residence times.Denser silica network structures with fewer hydroxyl impurities, shorter Si-O bonds, decreased Si-O-Si bond angles and a greater magnitude of isolated pores were found in films deposited with decreased precursor flux and increased plasma residence times, and consequently exhibited significantly improved encapsulation performance. a FUJIFILM Manufacturing Europe B.V.,

For the first time in atmospheric pressure-plasma enhanced chemical vapour deposition of amorphous silica onto flexible polymer substrates, pinholes have been visibly detected using interferometric microscopy and their average diameter of 1.7 μm calculated. Pinholes were found to control the water vapour transmission rate of all 30 nm films deposited with input energies greater than 9 keV per precursor molecule, thus presenting an opportunity for the synthesis of single layer thin films with precisely targeted permeation rates. The pinholes themselves were understood to originate from interactions between the polymer substrate and filaments in the plasma. The non-uniformity of the discharge was attributed to the reduced concentrations of precursor tetraethyl orthosilicate and oxygen species necessary to deposit amorphous silica at high specific energies.