High-performance water vapor barriers via amorphous alumina-polycrystalline zinc oxide hybrids with a self-wrinkling morphology

This work presents a materially and structurally designed barrier thin film with a self-wrinkling morphology, which consists of composites of amorphous alumina (a-Al 2 O 3 ) and polycrystalline zinc oxide (ZnO). The pure ZnO, Al 2 O 3 films, and Al 2 O 3 -ZnO composited film are deposited on polyethylene terephthalate (PET) by magnetron co-sputtering at room temperature. The water vapor transmission rate (WVTR) for the composited film with about 30 % ratio of Al 2 O 3 to ZnO is down to 0.026 g·m −2 ·day −1 from 1.184 g·m −2 ·day −1 of pure ZnO film at 38 °C/90 % RH, indicating that the nanocomposite structure of amorphous Al 2 O 3 and crystalline ZnO can significantly improve the water-resistance performance. Theoretical calculations demonstrate that the amorphous Al 2 O 3 can dramatically suppress the defect fraction within ZnO from 4.65 % to 0.08 %. Furthermore, a self-wrinkling morphology with Al 2 O 3 -ZnO composited film deposited on PET/acrylic is designed to have the WVTR value as low as 1.30 × 10 −3 g·m −2 ·day −1 . Due to the stress release when forming micro-scale wrinkles, the more smooth and dense Al 2 O 3 -ZnO composited film can markedly sharpen up the barrier property. The low WVTR barriers via amorphous and crystalline hybrid composites with self-wrinkling morphology by magnetron sputtering potentially serve as a low-cost and large-scale production path for electronics encapsulation as compared to atomic layer deposition (ALD) and plasma-enhanced chemical vapor deposition (PECVD). • Al 2 O 3 -ZnO film with an appropriate Al 2 O 3 ratio reduces water vapor transmission rate. • Amorphous Al 2 O 3 -crystalline ZnO hybrid film is deposited by magnetron co-sputtering. • A defect-mediated model for a single film on PET is proposed and applied to the system. • Al 2 O 3 -ZnO film with self-wrinkling morphology markedly sharpens up barrier property.