Water Vapor Permeation in Alumina Films on Polymer Substrates

Herein, the water vapor transmission rate (WVTR) of aluminum oxide (Al 2 O 3 ) films on polyethylene terephthalate (PET) substrates is investigated and is focused on the impact of the film defects on the transmission rate. The aluminum oxide films are prepared on PET substrates by magnetron sputtering, and the effects of the film thickness, sputtering power, temperature, and bias voltage on the WVTR are studied. The surface morphologies of the films are examined using atomic force microscopy (AFM), and a method for obtaining the defect ratio of the film from AFM images is proposed. Subsequently, the influences of the defect ratio on the WVTR are quantitatively evaluated based on a 3D diffusion model. The simulated WVTR values are well in agreement with the experimental ones.