Moisture resistance of the low-emissivity coatings with a layer structure of Al-doped ZnO/Ag/Al-doped ZnO

Abstract The moisture durability of sputtered low-emissivity (low-e) coatings with a single silver layer structure of ZnO/Ag/ZnO/glass and Al-doped ZnO/Ag/Al-doped ZnO/glass was investigated. Zinc oxide and aluminum-doped zinc oxide (AZO) films were reactively deposited from pure Zn, 99Zn1Al, 97Zn3Al, 95Zn5Al, 90Zn10Al (at.%) targets. The aluminum content in the AZO films was measured by secondary ion mass spectroscopy (SIMS). The deposition rate and internal stress of the AZO films were measured. After a moisture durability test at 50°C in 95% relative humidity for 12 days, the coatings were analyzed using optical microscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was observed that the Al addition reduced the internal stress of the oxide films, and the AZO/Ag/AZO coatings had a better moisture resistance. However, the Al addition led to a decreased deposition rate of the oxide films, and the addition of excess Al resulted in a different moisture degradation with a hazy appearance that might be due to an undesirable hydrate formation in the low-e coating.