Molecular dynamics simulations of nanoparticle sintering in additive nanomanufacturing: The role of particle size, misorientation angle, material type, and temperature

Additive nanomanufacturing, where nanoparticles (NPs) are generated via laser material ablation and sintered via laser, permits the fabrication of novel electronic devices with adequate flexibility, such as tunable material composition, adjustable sintered state, and a wide selection of substrates—including biodegradable ones—to name a few. The laser energy input often needs to be carefully balanced between achieving adequate sintering and avoiding substrate damage. The sintered state of NPs, a key influencing factor of the resistivity of electronic circuits, depends not only on temperature (the result of laser energy input), but also on NPs size, size ratio, and crystallographic misorientation. While the minuteness of NPs and the transient nature of their sintering (typically within a nanosecond) make direct experimental evaluation of such parameters challenging, the length and time scales are uniquely suitable for molecular dynamic (MD) studies. This study utilizes MD to investigate the sintering characteristics of silver and copper NP doublets at different temperatures and examines the effects of NP size, size ratios, misorientation angle (including both tilt and twist), and material type. A mathematical framework to describe the characteristic sintering time, i.e., time needed for a NP doublet to achieve a given normalized neck size, was proposed based on MD results.