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Direct writing of Cu-based fine micropatterns using femtosecond laser pulse-induced sintering of Cu2O nanospheres

Cu-based micropatterns were directly fabricated using femtosecond laser pulse-induced sintering of Cu2O nanospheres. Cu2O nanospheres synthesized by the polyol method were spin-coated on glass substrates. By evaluating the nonlinear optical absorption of the Cu2O nanosphere films using the Z-scan method, the two-photon absorption coefficient was estimated as ∼70 cm GW−1, which is adequate in comparison with that of bulk Cu2O. Although Cu and Cu2O composite micropatterns were obtained at a high scan speed of 100–1000 μm s−1, CuO micropatterns were formed at a low scan speed of 1 μm s−1. Compared with the femtosecond laser sintering of CuO nanoparticles using linear optical absorption, the width of line patterns obtained using Cu2O nanospheres was smaller at each pulse energy. These results suggest that two-photon absorption induced a decrease of the absorbed area, providing the small line width. This direct writing technique is useful for selective fabrication of Cu-based fine micropatterns.