Structure and optical properties of Au-polyimide nanocomposite films prepared by ion implantation

Au-polyimide nanocomposites have been synthesized by implanting different doses of $Au+$ ions in $100nm$ thick films of pyromellitic dianhydride-$4,4′$ oxydianiline polyimide, prepared by glow discharge vapor deposition polymerization. Unambiguous evidence of Au nanoclusters growth is found only at the highest implantation doses $(5×1016Au+∕cm2)$⁠. Structural, compositional, and optical characterizations show that the implantation induces the compactation of the initial film due to H and C loss. The resulting structure is a composite containing $2–3nm$ gold nanoparticles arranged in a layer of about $40nm$ and, just beneath the sample surface, a $15nm$ thick carbon-rich layer. Optical simulations suggest the presence of a gold-carbon core-shell structure in the nanoparticles.