Permeability and corrosion in ZrO2/Al2O3 nanolaminate and Al2O3 thin films grown by atomic layer deposition on polymers

Abstract

The authors studied moisture permeation and corrosion in Al2O3 and Al2O3/ZrO2 nanolaminate (NL) thin films grown by atomic layer deposition (ALD) at 100 °C on polyester substrates. A percolation model accurately described the dependence of permeation on the volume fraction of ZrO2 in the nanolaminates. As the fraction of ZrO2 was reduced to ∼0.5, moisture permeation in the NLs approached the measurement limit ∼1 × 10−4 g-H2O/m2-day, equivalent to Al2O3 with the same total thickness. However, resistance to corrosion by water was modestly better for Al2O3 than for the NL, and we proposed that corrosion in ALD Al2O3 films was associated with hydrogen incorporation and a consequent film chemical composition that is an oxy-hydroxide, AlOx(OH)3−2x. The authors present x-ray diffraction evidence for conversion of ALD Al2O3 to hydroxide corrosion products, AlO(OH) and Al(OH)3, after aging films in damp heat (85 °C/85% relative humidity) for two weeks.