A study of defects in ultra-thin transparent coatings on polymers

Abstract

Ultra-thin layers of SiO2 and SiN prepared, for example, by plasma-enhanced chemical vapor deposition (PECVD) are increasingly used as gas barriers on flexible polymeric materials and of plastic containers. Despite the excellent barrier properties provided by these materials, all published data show some residual permeation, even when the barrier coatings are relatively thick (≥70 nm). This residual permeation is attributed to the presence of microscopic defects in the coatings. In this article we present new techniques, based mainly on reactive ion etching in oxygen plasma, to render visible micrometeror sub-micrometer-sized defects in transparent ceramic films on polymers. These techniques can be used to visualize and better understand the origins of defects in these coatings on a microscopic scale, as well as for mapping and counting defect density on a macroscopic scale (tens of cm2 or more).Ultra-thin layers of SiO2 and SiN prepared, for example, by plasma-enhanced chemical vapor deposition (PECVD) are increasingly used as gas barriers on flexible polymeric materials and of plastic containers. Despite the excellent barrier properties provided by these materials, all published data show some residual permeation, even when the barrier coatings are relatively thick (≥70 nm). This residual permeation is attributed to the presence of microscopic defects in the coatings. In this article we present new techniques, based mainly on reactive ion etching in oxygen plasma, to render visible micrometer-or sub-micrometer-sized defects in transparent ceramic films on polymers. These techniques can be used to visualize and better understand the origins of defects in these coatings on a microscopic scale, as well as for mapping and counting defect density on a macroscopic scale (tens of cm2 or more).

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