Here, we report the fabrication of low-temperature sol-gel-derived aluminum oxide (AlOx) films via ultraviolet (UV) annealing and the investigation of their water vapor blocking properties by measuring the water vapor transmission rates (WVTRs). The UV annealing process induced the formation of a dense metal-oxygen-metal bond (Al-O-Al structure) at low temperatures (<200 degrees C) that are compatible with commercial plastic substrates. The density of the UV-annealed AlOx thin film at 180 degrees C was comparable to that of AlOx thin films that have been thermally annealed at 350 degrees C. Furthermore, the UV-annealed AlOx thin films exhibited a high optical transparency in the visible region (>99%) and good electrical insulating properties (similar to 10(-7) A/cm(2) at 2 MV/cm). Finally, we confirmed that a dense AlOx thin film was successfully deposited onto the plastic substrate via UV annealing at low temperatures, leading to a substantial reduction in the WVTRs. The Ca corrosion test was used to measure the WVTRs of AlOx thin films deposited onto polyethylene naphthalate or polyimide substrates, determined to be 0.0095 g m(-2) day(-1) (25 degrees C, 50% relative humidity) and 0.26 g m(-2) day(-1), respectively. (C) 2017 Elsevier B.V. All rights reserved.