Durability of Ultra-Thin Silver Films and Silver–Gold Alloy Films under UV Irradiation

Silver films (Ag) and silver–gold films (Ag–Au) with thickness \sim15 nm are coated on Bk7 glasses through thermal evaporation. After doping gold of 5.2%, the grain size of the Ag film reduces from 13.6 nm to 9.1 nm, also the surface roughness decreases from 1.45 nm to 0.94 nm. A UV lamp is used as the irradiation light source to accelerate the corrosion process in the atmosphere. After 17 h irradiation, the pure silver film surface turns dark, and the transmittances reduce from 350 nm to 500 nm, while the Ag–Au film degrades much less, almost negligibly after UV radiation. Additional x-ray photoelectron spectroscopy and atomic force micrographs data are provided to show atomic content of films and their surface morphologies. It is suggested that small grain size and high packing density of alloy film prevent reaction of silver with oxygen in the atmosphere, which leads to high stability of the Ag–Au film.