Comparison of the Coating Structure of Silicon-Based PECVD Coatings With Varying Organic Content

Abstract

This study examines the structural transition between plasma-polymerized silicon-oxide (SiO<inf>x</inf>) and silicon-organic (SiOCH) coatings with varying organic content. Using comprehensive characterization techniques on 13 samples with systematically varied oxygen-to-hexamethyldisiloxane ratios and energy densities, we found that SiO<inf>x</inf> barrier coatings unexpectedly exhibited higher porosity than SiOCH coatings. This suggests chemical composition impacts barrier performance more than nanopore structure. The transition from SiOCH to SiO<inf>x</inf> involves molecular-level structural reorganization, likely due to absent Si-C bonds in SiO<inf>x</inf> coatings, creating a more rigid SiO₂-like cage structure. These findings provide crucial insights into structure-property relationships of silicon-based plasma coatings, essential for optimizing gas barrier functionality in applications like food packaging.