Remarkable durability improvement under high humidity of Ag thin film where an Al or Ti nanolayer was deposited onto the surface

Abstract

Silver is known to exhibit the highest reflectance, however, it requires a protective coating at the surface due to its low durability. We studied durability under high humidity of Ag films where Ti or Al surface layer (1 or 3 nm thick) was deposited onto the surface of the Ag films by rf magnetron sputtering. The environmental test was carried out at 55 °C, 90% relative humidity for 16 h. After the test, considerable agglomeration occurred in the Ag single film, but not in Ti/Ag and Al/Ag films. Therefore, the passivation effect of the surface oxide nanolayer, which was formed by natural oxidation of the metal nanolayer, was confirmed. This effect also meant that the specular reflectance was kept high, even after the test. It is found that a Al (1 nm)/Ag film could maintain the highest reflectance among all the samples.