Highly-impermeable Al2O3/HfO2 moisture barrier films grown by low-temperature plasma-enhanced atomic layer deposition

Abstract Polymer substrates are essential components of flexible electronic applications such as OTFTs, OPVs, and OLEDs. However, high water vapor permeability of polymer films can significantly reduce the lifetime of flexible electronic devices. In this study, we examined the water vapor permeation barrier properties of Al 2 O 3 /HfO 2 mixed oxide films on polymer substrates. Al 2 O 3 /HfO 2 films deposited by plasma-enhanced atomic layer deposition were transparent, chemically stable in water and densely amorphous. At 60 °C and 90% relative humidity (RH) accelerated condition, 50-nm-thick Al 2 O 3 /HfO 2 had water vapor transmission rate (WVTR) = 1.44 × 10 −4 g m −2 d −1 , whereas single layers of Al 2 O 3 had WVTR = 3.26 × 10 −4 g m −2 d −1 and of HfO 2 had WVTR = 6.75 × 10 −2 g m −2 d −1 . At 25 °C and 40% RH, 50-nm-thick Al 2 O 3 /HfO 2 film had WVTR = 2.63 × 10 −6 g m −2 d −1 , which is comparable to WVTR of conventional glass encapsulation.