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This feature article presents insights concerning the correlation of plasma‐enhanced chemical vapor deposition and plasma‐enhanced atomic layer deposition thin film structures with their barrier or membrane properties. While in principle similar precursor gases and processes can be applied, the adjustment of deposition parameters for different polymer substrates can lead to either an effective diffusion barrier or selective permeabilities. In both cases, the understanding of the film growth and the analysis of the pore size distribution and the pore surface chemistry is of utmost importance for the understanding of the related transport properties of small molecules. In this regard, the article presents both concepts of thin film engineering and analytical as well as theoretical approaches leading to a comprehensive description of the state of the art in this field. Perspectives of future relevant research in this area, exploiting the presented correlation of film structure and molecular transport properties, are presented. [ABSTRACT FROM AUTHOR]

This study tracks the physical aging behavior of coated and uncoated ultra‐thin poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) films on silicon wafers based on the refractive index using ellipsometry. The measured refractive index directly correlates with the free volume and hence the physical aging progression. Plasma‐enhanced chemical vapor deposition (PECVD) creates coatings with different thicknesses and oxidation degrees onto PTMSP films. Compared to uncoated PTMSP films, the PECVD‐coated films show a reduction of the refractive index increase of more than two orders of magnitude for less than 10 nm thin SiOx coatings. In contrast, SiOCH films show only a minor impact. The results reveal the superior physical aging behavior of PECVD‐coated films compared to untreated PTMSP films. [ABSTRACT FROM AUTHOR]