Oxidation-free and ultra-smooth thin silver films grown on a copper seed layer

Silver (Ag) films have been the noble-metal choice in nanophotonics for different innovative applications. This work shows a simple and effective way to achieve atomically smooth, continuous Ag films (<; 10 nm) with the use of Cu (1 nm) seed layer. Compared to previous reports on Ge/Ag films, the use of Cu as seed layer material improves the surface roughness of Ag films (with RMS roughness <; 5Å over 10 μm x 10 μm area) and reduces the electrical resistivity by more than a factor of 2. In addition, due to the lower percolation thickness, the minimum thickness required to obtain a continuous Ag film down to 3 nm, which is much lower than reported in literature for Ag films, is produced.