The Influence of Humidity on the Mechanisms Involved in Laser-Induced Particle Ejection Experiments

Abstract

International audienceWe report on experimental investigations on the role of humidity in the laser cleaning technique which simply consists of direct irradiation of the contaminated surfaces. Submicrometer particles are ejected from silicon substrates by single nanosecond laser pulses. The measurements of particle removal efficiency (PRE), laser energy removal threshold, and ejection velocities as a function of the amount of residual moisture trapped on the surface were performed. For the laser parameters we used, we demonstrate that the particle removal results from mechanisms based on the momentum transfer from laser ablated species to the particles. For high laser fluences, a self-limited local ablation of the surface provides the cleaning force. For lower laser fluences, a competition between two humidity-based forces is evidenced: the capillary adhesion force and the explosive evaporation (of water traces) cleaning force. This demonstrates that the humidity plays a major role in the so-called dry laser cleaning technique which aims at meeting the future surface preparation requirements of the emerging nanotechnologies

Size scaling of mesoporous silica membranes produced by nanosphere mediated laser ablation

“…This is completely consistent with an expected deposited laser energy, which scales also linearly with the focusing power of the spheres (that is with the enhancement factor I/I 0 ). Only the measurements for sample 6 (558 nm) exhibit a saturation for high laser fluences revealing the self-limiting character of nanosphere mediated ablation, as already reported for experiments with nanosecond lasers [21].…”

Fabrication of microcraters on silicon substrate by UV nanosecond photonic nanojets from microspheres

“…Other sources of size dispersion result from effects such as local bilayers, and humidity. Any residual local humidity can for instance play an important role by changing the nature of the particle-substrate interface or eject the sphere by its explosive evaporation before substrate ablation, as established earlier [8,9]. A second interesting point is the observation of nano-craters on silicon though the fluence is well below the damage threshold of bare silicon, which is around 1 J/cm 2 with this laser [10].…”