3D metallic nanostructure fabrication by surfactant-assisted multiphoton-induced reduction

A method to gain small feature sizes on the fabrication of metallic structures with the aid of a surfactant as a metal growth inhibitor was presented. Structures consisting of silver nanoparticles were produced in the metal-ion aqueous solutions placed on a cover slip by irradiation with a mode-locked femtosecond laser. The width of the metallic structure is found to be smaller than the size of the diffraction limit of 690 nm, which is given by 1.22 λNA^-1. The concentration of nanoparticles is found to be higher at the center of the focused laser spot due to higher nucleation probability associated with the higher laser power. Microscopic images reveal that the free-standing silver pillar are measured with a minimum linewidth of 180 nm. The direct photoreduction of the metal ions with surfactants lead to 3D metal structures with resolution exceeding the diffraction limit of light.