Abstract
This paper presents copper (Cu) precipitation from a surfactant-added glyoxylic acid copper (GACu) complex ink through femtosecond laser multiple pulse-induced thermochemical precipitation to realize high resolution Cu direct writing. The influence of the surfactant (n-decanoylsarcosine sodium, NDSS) on the nonlinear absorption properties of GACu complex ink was explored. NDSS addition did not affect the molecule binding and single-photon absorption properties of GACu complex ink. However, nonlinear optical absorptions evaluated via the open aperture z-scan method revealed differences between the NDSS-added and non-added GACu complex inks upon femtosecond laser pulse irradiation. These findings imply that Cu nanoparticles were produced from the GACu complex ink through nucleation and surfactant-mediated growth, and these nanoparticles within the ink led to the saturable absorption of the subsequently irradiated pulses. Furthermore, by irradiating the pulses at repetition frequency of 5 MHz and a pulse number of 2×104, a minimum dot diameter of 1.6 µm was attained with NDSS-added ink, matching the laser spot diameter, without excessive precipitation due to thermal diffusion. This fundamental comprehension of the effects of the surfactant NDSS and pulse numbers on the Cu precipitation process can be applied to the direct writing of various materials.