Evaluation of particle size distributions produced during ultra-violet nanosecond laser ablation and their relative contributions to ion densities in the inductively coupled plasma

Abstract

Relative contributions to ion densities in the inductively coupled plasma (ICP) of particles of various sizes produced by laser ablation (LA) were investigated. Particles generated by 266 nm, ns LA of BaF 2 , CaF 2 , and a scandium aluminum alloy, characterized using SEM, consisted of hard and soft agglomerates, spherical particles, and irregularly-shaped particles. Although soft agglomerates and spherical particles were common to aerosols generated by LA in all cases, hard agglomerates appeared to be unique to the scandium aluminum alloy, while irregularly-shaped exfoliated particles were unique to the calcium and barium fluoride windows. The spatial distributions of Ca, Ba, and Sc ions in the ICP were determined from laserinduced fluorescence images taken with filters of pore sizes from 1-8 µm added in-line to the transport tube upstream from the ICP. In all cases, a significant fraction of the ions formed in the ICP originated from micron-sized particles. Differences in the penetration depths of nanometersized agglomerates and micron-sized particles were about 2 mm for Ca and 1 mm for Ba. Differences in the penetration depths of nanometer and micron-sized agglomerates observed in the case of aluminum scandium were much less significant. This suggests that micron-sized hard-agglomerates and nanometer-sized soft-agglomerates experience very similar vaporization patterns. Additionally, there was evidence that flow patterns in the transport tube affect the trajectories of particles entering the plasma.

Characterizing the Grating-like Nanostructures Formed on BaF2 Surfaces Exposed to Extreme Ultraviolet Laser Radiation

“…However, their spacing is at least by one order of magnitude greater than in the case of XUV-CDL irradiation and they often cross each other at certain angles while the lines of the XUV-LIPSS reported here are dominantly parallel. Even nanoparticles emitted from BaF2 irradiated by the nanosecond laser radiation often show a calcite crystal habitus and sharp edges [32]. This all indicates that laser-induced cleavage of alkali-earth halide crystals along the crystallographic planes can be observed in both the cases but with the long-wavelength laser radiation they have not been found to be as regular and uniform as observed on the XUV-CDL-illuminated surfaces in the present study.…”

“…It is clearly visible that the periodic nanostructures observed in the XUV-CDL irradiation experiment differ from the morphology of all the damage patterns observed on alkali-earth-halide surfaces exposed to radiation of various kinds in numerous studies reported earlier [26][27][28][29][30][31][32][33][34][35][36][37][38][39]. We should keep in mind that an attenuation length of 46.9-nm XUV-CDL radiation in BaF 2 is very short, i.e., only about 10 nm [40,41].…”