Controlled Plasmonic Nanowelding of Metal Nanoparticles under Ultrafast Laser Irradiation for Printable Nanocircuits

Construction of nanoscale building blocks (e.g., nanoparticles) has shown great potential in fabricating multifunctional nanounits with combined and adjustable performance. In this work, thermodynamic simulation based on a modified two-temperature model and plasmonic effects was developed to demonstrate the local energy evolution during plasmonic nanowelding. Incident laser energy was highly confined within the junction area of two nanoparticles, which was beneficial for localized and controlled nanoparticles sintering. Upon nanojoint formation, spatially limited heating induced by plasmonic effects resulted in partial melting along the interface region, which could be further enhanced by subsequent heat accumulation under multiple laser pulses irradiation. Due to the resultant large temperature gradient and rapid heating–cooling process (up to 4.4 × 1010 K/s), the amorphous interface region can be observed at the junction. Driven by the large-surface tension and fast atomic diffusion at the sintering neck, two nanoparticles tended to merge to form a large dimer. This plasmonic effect-induced nano confined energy will be reformulated with the changing morphologies. Nanowelding of two metal nanoparticles was stopped at a certain stage due to limited energy input. Optical and electrical performance of nanowelded metal nanoparticles can therefore be designed via this controlled nanowelding process. This ultrafast laser-induced plasmonic nanowelding shows great potential in precise construction of small-scale structures with a controlled formation process, which can be used for the fabrication of printable nanocircuits.