Laser Ablation Microanalysis

Laser Microanalysis permits to characterize a material rapidly and without much preparation. It also offers space-resolved and time-resolved capability. In Laser Ablation a micro-scale sampling is performed, and the laser-induced aerosol is characterized online, e.g. by means of plasma-source mass spectrometry. Here, a plasma (ICP or inductively coupled plasma) is used for the atomization, excitation and ionization. The latter is necessary for mass spectrometry (MS), while the former is for optical emission spectrometry (OES). Unfortunately the ICP destroys important fundamental information related to the chemistry, binding and molecular structure. For this purpose a direct ionization is desirable. A short-wavelength laser can do this, plus offer nano-scale spatial resolution.

Spot-resolved analysis is required to characterize the heterogeneity of solid materials, which can be done with a number of techniques (Fig. 1). By means of Laser ablation, coupled with various detectors (Fig. 2), spatially resolved analysis in the range of  microns is feasible in a few seconds. No special sample preparation is needed, and results are available within minutes. The sample is directly ablated by the laser, and in LIBS (Laser-Induced Breakdown Spectroscopy) the generated plasma-radiation is spectrographically analyzed; the ablated material, transported by a carrier gas, is analyzed by ICP-MS (plasma mass spectrometry) or ICP-OES  (plasma emission spectrometry) to achieve trace-level detection power and isotopic resolution. Compared to electron beam techniques, where heavy sample preparation is necessary, and limits of detection as low as part per million are not possible, laser microanalysis is a significant progress. Plus depth-profiling analysis can be done over larger thicknesses of tens of microns, with nano-scale depth resolution.

 

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Fig. 1 Capabilities of the major techniques for microanalysis.

We elaborated and further developed our laser microanalysis setup to measure in an automated and efficient way the largest possible element menu. To extend the specific analysis capabilities, detection via ICP-MS, ICP-OES and LIBS system is being integrated within a single system. Out “MATLAS" multi-spectroscopy system enable the analysis for a wide range of elements and materials, from metal to ceramic till polymers and biological samples, within a single laser shot. Finally, we have self-developed an extreme ultraviolet (EUV) laser with wavelength of 10-50nm, to radically enhance the analytical capabilities. The latter permits direct ionization without a secondary ionization source, e.g. ICP.

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Fig. 2 - Schematic of Laser Ablation coupled to various analytical systems, e.g. ICP-MS, ICP-OES.
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