In order to improve the heat insulating properties of low-emissivity coatings, it is necessary to reduce the electrical resistivity of their multilayer structure, which consists of an Ag layer and oxide layers. In this study, structures comprising glass/ZnO/Ag and glass/TiO2/ZnO/Ag were deposited by sputtering, and the effects of these layers on the electrical resistivity were investigated. For a ZnO layer deposited at low sputtering gas pressure, lower surface roughness reduced the electrical resistivity of the Ag layer. Also, it was found that the electrical resistivity could be further decreased by inserting a TiO2 lowermost layer between the substrate and the ZnO layer. The results of X-ray diffraction and X-ray reflectivity measurements showed that the decrease in resistivity was mainly due to the improved crystal orientation of the ZnO and Ag layers.

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Silver-based low-emissivity films have been studied to improve window insulation performance. We have reduced the resistivity of Ag in glass/ZnO/Ag structures by inserting a TiO2 in the lowermost layer. In another study, we have also found that the resistivity of Ag thin film can be reduced by changing the sputtering gas from Ar to Kr. In this study, both methods were adapted to achieve even lower resistivity and the factors involved were analyzed in detail. The lowest electrical resistivity achieved was 3.4 μΩ·cm for a combination of a glass/TiO2/ZnO/Ag structure and Kr gas sputtering, which was 22% less than that for a glass/ZnO/Ag structure with Ar gas sputtering. X-ray diffraction, atomic force microscopy, and secondary ion mass spectroscopy results indicated that the important factor influencing the electrical resistivity was a reduction in the amount of sputtering gas trapped in the Ag layer by depositing the layer using Kr gas.