Search

Herein, the water vapor transmission rate (WVTR) of aluminum oxide (Al2O3) films on polyethylene terephthalate (PET) substrates is investigated and is focused on the impact of the film defects on the transmission rate. The aluminum oxide films are prepared on PET substrates by magnetron sputtering, and the effects of the film thickness, sputtering power, temperature, and bias voltage on the WVTR are studied. The surface morphologies of the films are examined using atomic force microscopy (AFM), and a method for obtaining the defect ratio of the film from AFM images is proposed. Subsequently, the influences of the defect ratio on the WVTR are quantitatively evaluated based on a 3D diffusion model. The simulated WVTR values are well in agreement with the experimental ones. [ABSTRACT FROM AUTHOR]

A model for describing the diffusion behavior of water vapor in barrier films is developed and applied to the cases of 1) pure polyethylene terephthalate (PET); 2) an inorganic thin film (ITF) with defects on a PET substrate (ITF/PET); and 3) PET/ITF/PET. The normalized concentration profile and the relative mass of water vapor in the ITF/PET and PET/ITF/PET barrier films are simulated as a function of diffusion time by considering the sorption and desorption of water vapor. The number of atoms penetrating the barrier films is quantitatively evaluated by the concentration gradient of water vapor, which is related to the water vapor transmission rate (WVTR). The simulated WVTR values in pure PET, PET/SiOx, and PET/SiOx/ORM layered structures are in good agreement with the experimental ones. [ABSTRACT FROM AUTHOR]

• Water vapor transmission rate (WVTR) of inorganic layers on polymer is calculated. • Effects of amorphous/polycrystalline structures on barrier property are evaluated. • Al 2 O 3 /ZnO film on polymer has a better barrier performance than that of ZnO/Al 2 O 3. • The effect of inorganic layer thickness can be ignored if it excesses 100 nm. • The relative error between calculated and measured WVTR is less than 10%. The barrier performance of amorphous and/or polycrystalline inorganic oxide thin films deposited on flexible polyethylene terephthalate (PET) substrates is evaluated by a developed model that accounts for the diffusion of water vapor through the pinholes and grain boundaries, respectively, in amorphous and polycrystalline sublayers. Three-dimensional diffusion simulations are performed for modeling the influences of layer thickness, defect spacing and grain size on the barrier properties of single (multi) layer films. The water vapor transmission rate (WVTR) is calculated for single/multi-inorganic layers with different structures (amorphous and polycrystalline), numbers of inorganic layers and thicknesses. The simulation results show that the WVTR decreases exponentially with the increase of the inorganic layer thickness. According to the fitted results, the diffusion coefficient of water vapor in the defects (grain boundaries or pinholes) of inorganic materials is much smaller than that in PET, and the diffusion coefficient of water vapor in the grain boundaries of the polycrystalline inorganic layer (PIL) is close to that in the defects/pinholes of the amorphous inorganic layer (AIL). In comparison to PET/AIL, PET/PIL and PET/PIL/AIL films, the barrier performance of PET/AIL/PIL film is superior. As examples, PET/Al 2 O 3 /ZnO and PET/ZnO/Al 2 O 3 films were prepared for verification of the developed model. The simulated WVTR values agree well with the experimental ones. [ABSTRACT FROM AUTHOR]

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). [Display omitted] • 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. [ABSTRACT FROM AUTHOR]