Long-range surface plasmon polariton waveguides containing very thin spin-coated silver films

We fabricated very thin solid silver films with thicknesses below 50 nm using a spin coating method. An aqueous silver ionic complex solution was spin-coated and then thermally cured for a few minutes at a low temperature. The properties of the spin-coated silver films were compared to the properties of silver films deposited by thermal evaporation. The spin-coated thin silver films possessed silver crystallinity and a surface roughness of ~ 2.83 nm, while the thermally evaporated thin silver films also possessed silver crystallinity with a surface roughness of ~ 2.44 nm. Long-range surface plasmon polariton (LR-SPP) waveguides fabricated by both spin coating and thermal evaporation were also characterized and compared. The propagation losses of the 23 nm thick spin-coated and the 19 nm thick evaporated LR-SPP waveguides with strip widths of 7 μm were 3.6 and 4.2 dB/cm, respectively, and their coupling losses were 1.4 and 1.0 dB/2facets, respectively. The use of the spin coating method is a very cost effective solution because the films can be formed at low temperature in a short period of time without requiring a vacuum system. In addition, there are many potential applications of using spin-coated very thin solid silver films in LR-SPP waveguides and nano electrical circuit patterns.