Student Spectrometer-based Ultrashort Pulsed Laser Selective Microstructuring of Ni/NiCr Multi-layer CoatingsWednesday (24.06.2020) 11:59 - 12:02 Room 1
Microstructuring using ultrashort laser pulses is nowadays an established process for high precision manufacturing and has a broad spectrum of applications. This paper concentrates on the characterisation of the ultrashort pulsed laser ablation process of thermal sensitive Ni/NiCr thin layers deposited on Al2O3 substrates. The Ni and NiCr thin layers were coated by physical vapor deposition (PVD) process and had a mean thickness of approximately 2-3 µm. In order to achieve a material-defined ablation process, we firstly identified the removal threshold of Ni(0.4 J/cm²), NiCr(0.47 J/cm²) and Al2O3(1.1 J/cm²). The minimum removal depth in Ni and NiCr thin layers by a single laser scanning path were experimentally investigated and were 0.15 µm and 0.13 µm respectively. In addition, the Ni/NiCr single layer on Al2O3 substrate could be structured to a defined depth. Following that, with the aim to distinguish the ablated materials, we applied a UV-VIS-IR spectrometer to acquire the spectra of the laser-induced plasma generated during the ablation of the Ni and NiCr layers in the range 200 nm to 1100 nm. The characteristic peaks of chrome at 425.4 nm, 427.5 nm and 429 nm were detected. Based on the analysis on the plasma emission spectra, we can characterize the local ablated material composition, and thus perform a material-defined ablation process in the Ni/NiCr multi-layer system, which have very similar removal threshold values.
Compared with the profiling-based laser microstructuring the material-defined ablation process by means of spectroscopy offers several advantages such as high precision and efficiency. The spectrum of ablated material can be acquired within the minimum removal depth. Moreover, the process has great potential to enhance the controllability in microstructuring of thin layers with inhomogeneous thickness.
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