PECVD and PEALD on polymer substrates (part II): Understanding and tuning of barrier and membrane properties of thin films

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. Recent results on the analysis of plasma/polymer interactions and the nucleation of ultrathin plasma films by plasma-enhanced chemical vapor deposition and plasma-enhanced atomic layer deposition on polymeric substrates are shown. The adjustment of deposition parameters and substrate selection leads to either effective diffusion barriers or films with selective permeability. The discussion connects film growth and analysis of the pore size distribution and pore surface chemistry with transport properties of small molecules, encompassing concepts of thin film engineering with analytical and theoretical approaches.image