Picosecond laser writing of highly conductive copper micro-contacts from deep eutectic solvents

Techniques for local metallization of dielectric materials are widely applied for the design of various electronic devices. One of the most flexible methods for local contact fabrication is laser-induced chemical liquid deposition (LCLD) of metals from deep eutectic solvents (DES), which was performed using continuous-wave (CW) lasers. In this work, we applied picosecond laser pulses and proposed a novel method for DES layer deposition to increase the speed and quality typical for LCLD methodology that uses the CW lasers. As a result, the fabrication speed of the conductive copper structures was increased up to 10 mm sec-1. The electrical resistivity of these structures is 0.15 & omega; mm2 m-1, which is the best result among similar structures previously obtained by LCLD. Moreover, this modified LCLD method does not need to use a vacuum chamber or photomask, while the DES preparation and deposition by spin-coating is very simple. In addition, there is no complexity and instability associated with the synthesis of the metallic nanostructured materials using the proposed methodology, which are typical for the conventional laser direct writing technology. Finally, there is no need to carry out the post-treatments such as sintering or additional cleaning steps. In order to show the high quality of the formed contacts, we demonstrate the stable and reproducible operation of the commercial light-emitting diodes connected by the contacts made by the proposed technique.