On the synergistic effect of inorganic/inorganic barrier layers: an ellipsometric porosimetry investigation

In this paper, plasma-enhanced chemical vapor deposited SiO2 layers capped by an ultra-thin plasma-assisted atomic layer deposited Al2O3 over-layer are analyzed by means of ellipsometric porosimetry (EP). In a very recent contribution, we have shown that the combination of the two layers provided excellent intrinsic moisture permeation barrier performance down to the 10−5–10−6 g · day−1 · m−2 regime. The present paper therefore addresses the microstructural changes which the SiO2 layers undergo upon Al2O3 deposition, as monitored by ellipsometric porosimetry (EP). It was found that the Al2O3 deposition primarily affects the relative content of open pores with d > 0.3 nm (water as probe) and d > 0.42 nm (ethanol as probe) from 5.35 to 2.81% and from 2.50 to 0.32%, respectively.