Low-emissivity TiO₂/Ag_xCu_1-x/Ti/TiO₂ nano-multilayer films

A series of single AgCu alloy films and multilayer TiO₂/Ag_xCu_1-x/Ti/TiO₂ films with different silver concentration are prepared by DC magnetron sputtering. X-ray diffraction (XRD), scanning electron microscopy (SEM), scanning Auger microprobe, UV-VIS spectrophotometer, and infrared emissivity measurement are used to investigate the films. The optical, electrical properties of the single layer films and multilayer films before and after heat treatment are studied. The conductivity of alloy films declines with decreasing Ag concentration. If x is lower than 80%, the alloy is not appropriate to be the metallic layer in the multilayer films. Properties of pure silver film are modified after being heated at 150°C for 30 min in the air. Along with 10% decrease of luminous transparency and an increase of sheet resistance from 2.5Ω/□ to 20Ω/□ the infrared emissivity increases from 0.17 to 0.69. Little changes are observed for alloy films after heat treatment. TiO₂/Ag/Ti/TiO₂ and TiO₂/Ag₈₀Cu₂₀/Ti/TiO₂ nano-multilayer films keep good properties after being heated at 250°C in the air for 40 min, while the nano-multilayer films with other Ag concentration are modified obviously.