Ultrafast laser direct writing of highly conductive copper micropatterns

Copper (Cu) interconnects are fundamental to advanced optoelectronic systems. Femtosecond laser direct writing (FsLDW) employing particle-free Cu ion inks provides a compelling “cold processing” approach; however, it frequently results in porous, high-resistivity structures caused by disordered grain growth and solvent-induced micro-explosions. Here, we report a high-precision FsLDW strategy utilizing a specifically formulated metal-organic complex ink. By decreasing the reduction energy barrier and regulating crystallization via a composite amine complex, combined with a pre-baking step to suppress micro-explosions, we achieve Cu micropatterns with a highly dense surface morphology under ambient conditions. The resulting structures demonstrate a minimum resistivity of 9.34 μΩ·cm (approximately 5.5 times that of bulk Cu) while maintaining sub-10 μm linewidths. Moreover, this method exhibits broad processing adaptability and substrate compatibility, facilitating reliable metallization on flexible substrates, macroscopic wafers, and curved surfaces. The fabricated Cu interconnects function as stable signal and power transmission pathways within a fully FsLDW-patterned UV photodetector. This study establishes a practical route for deploying high-performance conductive networks in advanced electronic systems.