Chemical imaging using microline laser ablation: performance comparison of Gaussian and flat top lasers

In previous studies, the potential of a microline imaging arrangement for surface characterization of solid samples in air at atmospheric pressure using laser-induced plasma spectrometry (LIPS) has been demonstrated. An improvement of this approach to obtain a uniform ablation along the microline focus that leads to a representative spatial distribution of elements on the sample surface is presented. For this purpose, the influence of beam energy distribution of two types of Nd:YAG pulsed lasers (a Gaussian laser and a flat top laser) on lateral resolution, intensity profiles of elements, chemical distribution maps, and plasma electron temperature has been investigated. As models of homogeneous and compositionally patterned samples, a stainless steel sample and a photovoltaic cell were chosen for this study. The results demonstrated that the Gaussian laser provides the best lateral resolution, but more redeposition at both sides of the microline crater, while the chemical maps obtained with the flat top laser matched with the distribution of the constituents of the sample surface.