Dynamic ellipsometric porosimetry investigation of permeation pathways in moisture barrier layers on polymers

The quality assessment of moisture permeation barrier layers needs to include both water permeation pathways, namely through bulk nanoporosity and local macroscale defects. Ellipsometric porosimetry (EP) has been already demonstrated a valuable tool for the identification of nanoporosity in inorganic thin film barriers, but the intrinsic lack of sensitivity toward the detection of macroscale defects prevents the overall barrier characterization. In this contribution, dynamic EP measurements are reported and shown to be sensitive to the detection of macroscale defects in SiO2 layers on polyethylene naphthalate substrate. In detail, the infiltration of probe molecules, leading to changes in optical properties of the polymeric substrate, is followed in time and related to permeation through macroscale defects.