A study of thin film encapsulation on polymer substrate using low temperature hybrid ZnO/Al ₂O ₃ layers atomic layer deposition

Hybrid ZnO/Al ₂O ₃ layers grown by atomic layer deposition (ALD) at extremely low temperature (60 °C) have been investigated as thin film encapsulations (crystalline ZnO and amorphous Al ₂O ₃ films) on polymer substrates. All single and laminated film thicknesses are approximately 60 nm. As the thickness of ZnO layer decreased from 60 nm to 0 nm, the physical properties of laminated structures were systematically manipulated such as film crystallinity, surface roughness, density, transmittance and stress. The multi-laminated structure with 10 nm thick ZnO and 10 nm thick Al ₂O ₃ layers exhibited very lower crystallinity, smoother surface (root mean square ∼ 0.2 nm), higher transmittance (over 90% at 550 nm wavelength) and similar film stress, to compare with these of a single ZnO film. As a transparent gas barrier layer, the multi-laminated structure with a thinner ZnO and Al ₂O ₃ had better barrier property than that of single ZnO and Al ₂O ₃ layers, showing that the water vapor transmission ratio of multi-laminated ZnO/Al ₂O ₃ layer was 10 times lower than that of the single layer.