Highly stable silver thin films utilizing aluminum nanolayers

Silver (Ag) has excellent properties such as low resistivity and high reflectance. However, Ag thin films on oxide substrates have the disadvantage of agglomeration by annealing due to poor adhesion to the substrates and easy migration of Ag atoms. In this paper, multilayer films with Al nanolayers at the surface and interface were prepared and annealed up to 600 °C in vacuum. It was found that agglomeration was remarkably suppressed compared to Ag single film. In addition, other metals were also investigated as surface nanolayers and the main properties required for them were clarified. Then, the Al and Ti surface nanolayers were deposited on Ag films and their optical properties and durability under high humidity were investigated. We found that Ag films deposited with 1 nm Al or Ti layer showed the same reflectance as silver single film. After the environmental test at 55 °C, 90% relative humidity for 16 h, considerable agglomeration occurred in the Ag single film, but not in the Ti/Ag and Al/Ag films. As a result, the specular reflectance of the multilayers remained high even after the test. It was also confirmed that the protective layer should be continuously deposited on the Ag film in vacuum to achieve the highest agglomeration suppression effect.