Oxide nanoparticles embedded in a polyimide film

Abstract

We developed a simple method of producing metal oxide nanoparticles by reacting a polyamic acid (PAA) with metal films. A thin layer of polyimide precursor, polyamic acid (PAA) was spin coated on the Copper, Zinc, Iron, and Tin thin films, then the film stacks were baked at 135℃ for 30 min to remove the solvent and cured in N2 atmosphere at various temperatures up to 400℃. Respective particle size, distribution, and morphology were characterized by transmission electron microscopy (TEM). Very small Cu2O, ZnO, Fe2O3 or SnO2 nano-particles were observed in the polyimide film. The size and the density of metal oxide nanoparticles depended on the curing temperature. The degree of imidization and the mobility of particles have strong effect on the formation of metal oxide nanoparticles. The morphology and the distribution of metal oxides dispersed in the polyimide depended on the metal type. The Cu2O or ZnO particles were formed by the dissolution reaction between the polyamic acid and the Cu or Zn films. During curing, PAA dehydrates and converts to polyimide, accompanied by precipitation of Cu2O or ZnO particles. The synthesized Cu2O or ZnO particles were randomly dispersed within the polyimide. On the other hands, the Fe or Sn film undergoes surface reaction with the polyamic acid. Therefore, the synthesized Fe2O3 or SnO2 particles existed only at the surface of the substrate. The different particle distributions were attributed to the reactivity difference of PAA with metal films. This method of preparing oxide nano-particles can be easily extended to other oxide systems as demonstrated and the resulting morphology and size distribution can be controlled by altering