Comparative Investigation of LIBS Spectra and Crater Morphology During Laser Ablation of Eutectic BiSn Alloys
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Laser-based methods such as pulsed laser deposition (PLD) that are used for fabricating structural and functional materials are ripe for dramatic improvement. However, because laser–material interactions are dependent on detailed and largely unknown processes that occur during the laser ablation, the ability to control the resultant thin-film stoichiometry remains a significant challenge. Unfortunately, resolving those problems is hindered by additional critical gaps in our knowledge such as the evolution of the crater morphology, the degree of consistency in elemental composition between the target material and the plasma plume, and the ablation thresholds for different materials. This dissertation research presents a novel approach for monitoring material transfer during the ablation process of eutectic Bismuth-Tin (BiSn) alloys as the investigated material. A nanosecond excimer pulsed Ultraviolet (UV) laser was used to ablate the targeted alloys. Laser-Induced Breakdown Spectroscopy (LIBS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and optical profilometer techniques were used to characterize the plasma plume and the morphology and elemental distribution of the craters, post ablation. The proposed approach was successfully applied and confirmed the influence of the aforementioned parameters on the stoichiometric transfer during the ablation process. It has been shown that ablation thresholds are affected by the physical properties of the target material, e.g., the melting point. Additionally, the surface morphology and the parameters of the laser have a significant impact on the plasma parameters where higher plasma temperatures and electron densities were observed with deeper craters. Finally, it was shown that the ablation rate tends to decrease in the case of multi-pulse laser ablation compared to the single pulse method. The comparison between the plasma plume and the crater morphology of the investigated targets demonstrates a successful combination of LIBS and PLD to create a real-time monitoring tool for quality control and stoichiometric transfer during thin-film fabrication.
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Introduction -- Background -- Materials and methods -- Results and discussion -- Conclusion
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Ph.D. (Doctor of Philosophy)