Effect of copper nanoparticle addition on the electrical and optical properties of thin films prepared from silver nanoparticles

The fabrication of transparent and conductive silver (Ag) and copper (Cu)-doped Ag films using simple spin-coating method with Ag and Cu nanoparticles (NPs) as starting material is described in this study. The aggregation of Ag NP and the grain formation caused by heat treatment were hindered by the addition of small amount Cu NP, and a continuous film was obtained even though the thickness was in the order of 10 nm. When the total metal concentration of NP solution precursor was 5 wt% with the ratio between Ag and Cu being 95:5, the surface resistivity (ρ_s) of Ag–Cu film was 3.17 Ω/sq; and when the concentration was reduced to 3.5 wt%, the ρ_s was 16.3 Ω/sq. The transmission of latter was more than 60 % with the maximum value 82.1 % at 328 nm in the near-UV region (300–400 nm), however, decreased to about 38 % in the visible region (400–700 nm) and near-IR region. The inhomogeneity of the film increased leading to the decrease of the conductivity with the time extension during the heat treatment.