Direct writing of metal/metal oxide microstructures using femtosecond laser pulse-induced photothermochemical reduction

Abstract

Direct writing of metal/metal oxide microstructures using femtosecond laser pulse-induced photothermochemical reduction is demonstrated. Two-dimensional/three-dimensional (3D) microstructures were fabricated using linear optical absorption-induced thermochemical reduction of CuO, NiO, and their mixed nanoparticles. Cu-rich and Cu₂O-rich patterns were selectively formed by controlling the degree of reduction of CuO nanoparticles by changing the writing speed. Thermosensors such as a thermistor-type Cu-rich/Cu₂O-rich sensor and thermoelectric-type Cu₂O/NiO (p-type) and Cu–Ni-rich (n-type) sensor are demonstrated. In addition, Cu-based 3D microstructures were fabricated using nonlinear optical absorption-induced thermochemical reduction of Cu₂O nanospheres. The thermochemical reduction was induced around the focal spot inside the nanosphere ink. Such direct writing technique is useful for fabrication of microdevices consisting of various functional materials.