Effects of surface pretreatment and deposition conditions on the gas permeation properties and flexibility of Al 2 O 3 films on polymer substrates by atomic layer deposition
Journal
Journal of Coatings Technology and Research
Date Issued
2019
Author(s)
Abstract
The effects of surface pretreatment and deposition conditions on the gas permeation properties—including permeability of He, O2, and H2O; the size; and the density of permeation-enhancing defects—and mechanical flexibility of Al2O3 films on polymer substrates by atomic layer deposition (ALD) were investigated to develop flexible gas barrier films for organic and flexible electronics. Pretreating polyimide (PI) and poly(ethylene terephthalate) (PET) substrates with an aqueous KOH solution greatly lowered the gas permeability of the ALD Al2O3 films as a result of improved affinity between the substrate surface and the ALD precursors. Varying the ALD conditions—including lengthening the precursor exposure, elevating the deposition temperature, and changing the precursor sequence—enhanced physisorption of ALD precursors on the polymer substrate, which improved nucleation of the ALD films to reduce defects in the films and lower their gas permeability. Activation energy for permeation determined from the temperature dependence of the permeability of the ALD films indicated that the ALD films deposited under the optimized condition contained smaller and few permeation-enhancing defects. The optimized ALD films possessed a low water vapor transmission rate of ~ 10−6 g/m2 day that met the stringent requirement of organic and flexible electronics, while also exhibiting excellent mechanical flexibility by withstanding repeated bending with small increases in gas permeability. Our results provide valuable insights into the development of flexible barrier thin films for the encapsulation of organic and flexible electronics.
Type
journal article