Short laser pulse nanostructuring of metals: direct comparison of molecular dynamics modeling and experiment

Laser-induced forward transfer of pure metals

“…A nanobump is a smooth bump in the metal film, which is observed below the ejection threshold fluence, which is however distinctly different from the commonly reported LIFT ejection by formation and break-up of a liquid filament [42,48]. The dynamics of liquid phase nanobump formation were recently theoretically investigated using molecular dynamics simulations, revealing significant thinning of the donor film at the base of the bump [40]. However, cap ejection was not reported, since the simulations were limited to short timescales or sub-ejection fluence levels.…”

“…Elastic stress release and partial vaporization of the film are well-established driving mechanisms for metal LIFT [35,36,[38][39][40]54]. However, the actual driving mechanisms are more complex.…”

“…However, the actual driving mechanisms are more complex. For example, numerical simulations by several authors revealed that cap-ejection regime is the result of a heat-induced elastic pressure wave traveling perpendicular to the film [38][39][40]54]. This wave is reflected at surface of the donor-air interface and induces pull-off of the donor from the carrier.…”

“…Therefore, theories describing the ejection mechanism have been proposed based on postprocess analysis of the craters left in the donor layer or deposited features on the receiver substrate [35][36][37]. In addition, numerical simulation has been performed [38][39][40]. Two driving mechanisms of the ejection process are commonly proposed [35,36,41].…”

“…Therefore, thermal compression of the metal film and subsequent release of elastic energy is proposed as the driving mechanism as proposed by Veiko et al [36] and by Ivanov et al [40]. To further study the characteristics of this driving mechanism, the elastic energy E E in the donor layer is modeled as…”