Characterization of Nanoparticles Fabricated by Oxidation of Ni₈₀Fe₂₀ and Co₈₀Fe₂₀ Thin Films during Imidization

Metallicnanoparticles embedded in a polyimide (PI) matrix were fabricated through selectively oxidizing a layer of Ni 80 Fe 20 metal film sandwiched between two PI precursor layers. Ni nanoparticles, formed in a monolayer between two PI layers, had an average particle size of ∼5 nm. X-ray photoelectron spectroscopy confirmed that Fe in the film was preferentially consumed, resulting in formation of Ni nanoparticles. Similar experiments to produce uniform-sized Co nanoparticles failed to produce uniform-sized Co nanoparticles when a Co 80 Fe 20 film was inserted because, unlike Ni, Co was partially oxidized during imidization. Transmission infrared spectroscopy suggested that thermal degradation of the PI matrix was catalyzed by the Co 80 Fe 20 film, leading to the Co oxidation together with Fe.