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

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 excell ent barrier properties provided by these materials, all published data show some residual permeation? even when the barrier coatings are relatively th ick (greater than or equal to 70 nm). This residual permeation is attribute d to the presence of microscopic defects in the coatings. In this article we present new techniques, based mainly on reactive ion etc hing 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 coa tings on a microscopic scale, as well as for mapping and counting defect de nsity on a macroscopic scale (tens of cm(2) or more). (C) 1999 Elsevier Sci ence S.A. All rights reserved.