Three-dimensional topographic and multi-elemental mapping by unilateral-shift-subtracting confocal controlled LIBS microscopy

Abstract

Laser induced breakdown spectroscopy (LIBS) is a promising analytical technique based on the interaction between laser and material, which can quantitatively analyse the composition and content of material from the perspective of spectroscopy. The element distribution of non-uniform samples, such as natural ore, can be obtained by pointwise scanning without pretreatment. LIBS excitation intensity is the highest near the focus, so low imaging speed and low focusing accuracy will lead to unreliable element maps. Hence, an ultrasensitive technique called unilateral-shift-subtracting confocal controlled LIBS microscopy (UCCLIBS) was prepared to rapidly acquire high spatial resolution multi-elemental maps of the sample surface, which utilizes a laser induced breakdown spectrometer attached to a unilateral-shift-subtracting confocal microscope. A surface axial focusing ability of approximately 18 nm under 20× objective lens with the N.A. value of 0.4 is obtained, which is more than two orders of magnitude higher than that of ever traditional LIBS approaches, and the inherent anti-drift capability is successfully realized. The chemometric method of principal component analysis (PCA) is applied to the multi-element analysis of agate ore, which improved the accuracy and efficiency of sample analysis. We show the multi-layer element map of a solid-state electrolyte with a tomographic resolution of 2.3 μm. With these excellent properties, the UCCLIBS might provide a new idea for the detection of three-dimensional elemental characterization of minerals and chemical materials.