Germanium Wetting Layers’ Dimensional Effect in Structural and Optical Properties of Silver Films

The peculiarities of light absorption in silver films of different thickness (2–20 nm) deposited on germanium underlayers of different mass thickness are experimentally investigated. The conditions of percolation transition in 5 nm thick silver films deposited on germanium underlayers in the range of 1 nm are studied. The influence of germanium underlayers with a mass thickness up to 1 nm with a step of 0.2 nm in the visible and near-infrared wavelength range (300–2500 nm) on the above-mentioned properties of silver films is investigated. Optical percolation in silver films is associated with the peculiarities of growth mechanisms and modes of formation of metal condensate on an amorphous glass substrate. As shown, the germanium underlayers previously applied to the glass substrate reduce the threshold thickness of the optical percolation transition in the silver film and increase their absorbency compared to similar films formed on a clean glass surface. The increase in the absorption capacity of films deposited on the surface of the germanium underlayer is due to a decrease in the average linear size of crystallites compared to similar samples formed on a clean glass surface, and thus, an increase in the number of scattering metal centres per unit surface area.