High rate roll-to-roll atmospheric atomic layer deposition of Al2O3 thin films towards gas diffusion barriers on polymers

Abstract In this study, Al 2 O 3 thin films fabricated through a novel technique of roll-to-roll atmospheric atomic layer deposition (R2R-AALD) using a multiple slit gas source head have been tested as low permeability gas diffusion barriers on polyethylene terephthalate (PET) substrate. The Al 2 O 3 deposition was carried out at a very low temperature of 50 °C under the working pressure of 740 Torr, which is very close to the atmospheric pressure (760 Torr). Good morphological, chemical, and optical characteristics have been shown by the Al 2 O 3 films produced at a large scale. The growth of Al 2 O 3 films has been confirmed by X-ray photoelectron spectroscopy (XPS), indicating the peaks of Al 2p, Al 2s and O 1s at the binding energies of 74 eV, 119 eV and 531 eV, respectively. On the basis of MOCON test instrument, water permeation values of the range ~10 −3  g/m 2 /day at 37.8 °C/100% relative humidity have been observed for Al 2 O 3 films with a thickness of 15 nm to 40 nm. Al 2 O 3 thin films with such low water permeability have not been reported before to be fabricated under near atmospheric pressure through any trend of roll-to-roll atomic layer deposition.