Silver disposition and dynamics during electroless metal thin film synthesis

Morphological and physicochemical disposition of silver (Ag) during redox-driven self-assembly of metal films on silica surfaces under equilibrium hydraulic conditions has been examined in real time in a novel electroless (EL) metal deposition cell by transmission UV-vis (T-UV) spectroscopy. Optical features due to localized surface plasmon resonance, surface plasmon polaritons, and photoluminescence from Ag and gold (Au) nanoarchitectures such as particles, clusters, and films were attributed by correlating T-UV with time-resolved scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Silver that deposited onto tin-sensitized surfaces in thin films nucleated nanoparticles when exposed to reductant or broadband light. Kinetic changes in plasmon features suggested four previously unrecognized time-dependent physicochemical regimes occur during consecutive EL deposition of Ag and Au onto tin-sensitized silica surfaces: self-limiting Ag activation; transitory Ag nanoparticle formation; transitional Au-Ag alloy formation during galvanic replacement of Ag by Au; and uniform metal deposition under controlled hydraulic conditions. Growth mechanisms at the surface, interior, and interface of the resulting thin metal films inferred from real time T-UV spectra were characterized by depth profile XPS analysis.