Abstract
Atomic layer deposition has become an important thin-film growth technique for producing gas diffusion barriers because of its low process temperature and its ability to produce uniform films. In this work, atomic layer deposition was used to deposit various Al2O3 and ZnO thin films on polyethylene terephthalate substrates; subsequently, the physical properties and water vapor transmission rates of the films were characterized. Single and hybrid films (Al2O3, ZnO, Al2O3/ZnO, and ZnO/Al2O3) with thicknesses of 25, 50, and 100 nm at a deposition temperature of 60°C were investigated. The deposited films were characterized for surface roughness, optical transmittance, adhesion, water vapor transmission rate, and contact angle. The results showed that the double-layer structure provided a higher water vapor transmission rate and higher adhesion strength than those of the single-layer structure although both the surface roughness and optical transmittance of the single-layer structure were slightly better than those of the double-layer structure. The results revealed that the atomic layer deposition-grown hybrids could act as water vapor barriers.
Highlights
Atomic layer deposition (ALD) has become an important thin-film growth technique because of its precise control over the thin-film thickness, its ability to produce uniform films over large areas, and its low process temperature.[1,2,3] ALD can be employed at sufficiently low temperatures to deposit various high-quality thin films on thermally fragile or flexible substrates
The results indicated that the adhesion strength of the ZnO film was higher than that of the same thickness Al2O3 film; it indicated that thicker films had higher adhesion strength
The single-layer adhesion strength carried by scratch is shown in Figure 4, where the error bars indicate the smallest and highest values of five parallel measurements; the adhesion strength of ZnO/polyethylene terephthalate (PET) was found to be slightly higher than that of Al2O3/PET with the same thickness
Summary
Atomic layer deposition (ALD) has become an important thin-film growth technique because of its precise control over the thin-film thickness, its ability to produce uniform films over large areas, and its low process temperature.[1,2,3] ALD can be employed at sufficiently low temperatures to deposit various high-quality thin films on thermally fragile or flexible substrates. Hirvikorpi et al.[5] used ALD to deposit thin and highly uniform Al2O3 coatings on various polymeric materials They found that the ALD-grown Al2O3 coatings significantly enhanced the oxygen and water vapor barrier performance of these materials. Mauro et al.[9] deposited ZnO thin films on polymeric substrates by ALD at a low deposition temperature and revealed that the ALD-grown ZnO thin film could be a high-quality flexible photocatalyst. Elam and collegues[2,10] studied the growth rate and surface roughness of ZnO/Al2O3 films. They found that the properties of the composite films can be tuned by changing the composition and interfacial density. Further observations of the water vapor transmission rate (WVTR), surface roughness, contact angle, and optical transmittance of the ALD films were studied
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