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

• Al2O3 thin films are fabricated by a novel technique of roll-to-roll atmospheric ALD.
• Films are grown with appreciable growth rates at 50 °C.
• Good morphological, chemical, and optical properties were shown by the Al2O3 films.
• Low water permeation values of~6×10−3 g m−2 day−1 were recorded for the films.

In this study, Al2O3 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 Al2O3 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 Al2O3 films produced at a large scale. The growth of Al2O3 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/m2/day at 37.8 °C/100% relative humidity have been observed for Al2O3 films with a thickness of 15 nm to 40 nm. Al2O3 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.