Vapor phase formation of a well-ordered aldehyde-terminated self-assembled monolayer on a SiO2 surface and formation of silver film on the surface based on the silver mirror reaction

A well-ordered aldehyde (CHO)-terminated self-assembled monolayer (SAM) was formed from a vapor of triethoxysilylundecanal (TESUD) onto both quartz glass plates and silicon substrates covered with native oxide. This vapor phase treatment produced a TESUD-SAM on both substrates without any marked change in surface morphology, as evidenced by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The thickness of this SAM was estimated by ellipsometry to be 1.2 ± 0.1 nm. Silver (Ag) metallization was also demonstrated on TESUD-SAM-covered quartz glass substrates based on the silver mirror reaction using an ammoniacal silver nitrate solution. XPS and AFM images confirmed that the deposited film was composed of densely packed Ag nanoparticles with an average diameter of 300 nm. The average thickness of the film was about 1–2 μm. Due to this particulate Ag film formation, the transparent insulating quartz glass plate became conductive with a mirror-like surface. The CHO terminal groups of the TESUD-SAM were found to serve effectively as a reducing agent to deposit Ag metal at the solid/liquid interface.