Defect characterization of silver-based low-emissivity multilayer coatings for energy-saving applications

Low-emissivity optical coatings, which provide high-efficiency heat isolation, are deposited onto architectural windows to be employed in offices and residential buildings for the purpose of saving energy. In the present work, multilayer low-emissivity coatings with the structure glass/SnO2(380 Aa)/Ni-Cr(10 Aa)/Ag(90 Aa)/Ni-Cr(30 Aa)/SnO2(380 Aa) were deposited in an industrial sputtering system onto large glass substrates. The extremely low thickness of the layers which compose such structures, as well as the large substrate area, makes the morphology of the films and interfaces play an important role in providing efficient energy saving performance as well as high optical transmittance. Questions such as the cleaning process of the substrate previous to deposition, partial pressure of the gasses in the sputtering system, etc., will affect the overall behavior of the coatings. The resulting morphology and composition of the films and interfaces was studied by optical microscopy, scanning electron microscopy energy dispersive x ray, atomic force microscopy, and Auger electron spectroscopy. Some structural defects that might affect the long-term stability of the coatings were found. Furthermore, the effect of aggressive environments on the low-emissivity multilayer coatings was tested, both from the structural and optical points of view