Precipitation of gold nanoparticles on insulating surfaces for metallic ultra-thin film electroless deposition assistance

In this work, the kinetics of 15 and 25 nm gold nanoparticle (AuNP) precipitation on silanized SiO2/Si surfaces were studied. The NP coverage as well as distribution on the substrates was explored. It was found that at the beginning of the process, the 25 nm AuNPs precipitate faster than their 15 nm counterparts. However, early saturation and low final surface coverage by these NPs were observed. The 15 nm AuNPs, exhibited higher (∼40%) surface coverage and precipitation saturation only after longer treatment times. This makes small NPs a promising candidate for catalyzing the deposition of ultra-thin metallic films on insulating substrates. In addition, it has been demonstrated for the first time that NPs, independently of their size, precipitate with a certain regularity and order. Using high-resolution scanning electron microscopy (HRSEM) it was observed that NPs are organized in pairs, and in each pair they are located at 50–60 nm from each other and under certain angle.