  This feature article presents insights concerning the correlation of PECVD
and PEALD 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. Moreover, based on the
presented correlation of film structure and molecular transport properties
perspectives of future relevant research in this area is presented.
