Photochemical selective deposition of nickel using a TiO2–Pd2+ layer

The mechanism of photochemical selective deposition of nickel employing an amorphous TiO2–Pd2+ layer with entrapped oxalic acid as a sensitizer has been studied by X-ray photoelectron spectroscopy, FT-IR spectroscopy, and TEM, SEM and AFM analyses. Exposure of TiO2–Pd2+ layers to UV light is believed to yield predominantly Pd(I) compounds stabilized in a photopolymerized matrix of titanium oxide. These compounds are capable of undergoing disproportionation during washing, which results in completion of Pd nanophase formation at the exposed areas. Increasing the UV light intensity from 8 to 30 mW cm−2 affects the structure and size of the obtained Pd particles and their catalytic activity towards nickel electroless plating. As a result, both negative and positive patterns can be obtained employing the same TiO2–Pd2+ photolayers.