Application of Atomic Layer Deposition for Gas Permeation Barrier Thin Films

Abstract

We determined by a Ca-test with optical modeling that a 25 nm thick Al2O3 film, grown by atomic layer deposition on polyester, reduced the effective water vapor transmission rate to < 10-5 g-H2O/m2-day. This is a reduction of more than 105x compared to the bare polyester. The corresponding diffusion coefficient for water vapor through this film was calculated to be D=2.5x10-17 cm2/s, and the threshold thickness for barrier properties was ~ 5 nm of Al2O3. We further concluded that these values were likely at the lower limit of this Ca-test method, because of edge diffusion of gas through the epoxy seal in the test structure.