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Picosecond and femtosecond pulsed laser ablation and deposition of quasicrystals (Articolo in rivista)

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Picosecond and femtosecond pulsed laser ablation and deposition of quasicrystals (Articolo in rivista) (literal)

Anno

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Alternative label

R. Teghil, L. D'Alessio, A. Santagata, M. Zaccagnino, D. Ferro, DJ. Sordelet (2003)
Picosecond and femtosecond pulsed laser ablation and deposition of quasicrystals
in Applied surface science
(literal)

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R. Teghil, L. D'Alessio, A. Santagata, M. Zaccagnino, D. Ferro, DJ. Sordelet (literal)

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Laser ablation and deposition technique is nowadays widely used for a large number of applications such as micro-machining, film deposition, laser drilling etc. However, one of the main problems related to its use is due to the need of controlling and understanding fully the whole experimental process parameters. For this reason the scientific importance of this work regards the experimental data and ablation mechanism hypothesis that give the opportunity of considering how the laser ablation and deposition process is affected by the laser beam pulse duration. As matter of fact, the valuable new experimental results have already provided the basis for formulating theoretical ablation mechanism models (e.g. one-dimensional hydrodynamic Lagrangian model) as well as new film deposition routes such as nano-particles structured coatings. (literal)

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The experimental work here performed has highlighted the main features governing the ablation mechanism involved during ultra-short laser ablation of quasicrystalline materials. First of all, spatial and temporal emission spectroscopy diagnostics have pointed out how 250 fs and 1.3 ps laser pulses induce plasma plume formation having different spatial distribution and dynamics than those due to a 6 ns laser source. Moreover, by employing ultra-short pulses the presence of trimer clusters, not detectable by the employment of the ns laser beam, have also been shown. The presence of these clusters during the plasma expansion has been considered as indicators of larger assembly precursor, which lead to nano-particles depositions. On the contrary of films obtained by the ns laser beam, the ones accomplished by both fs and ps laser pulses have shown the same stringent target material stoichiometry. The ablation mechanism induced by ultra-short lasers has therefore demonstrated how the ns ablation and deposition technique drawbacks can be overcome by choosing proper laser pulse duration. Finally, as a consequence of the experimental results obtained, one can consider that ultra-short pulses ablation mechanism involve strong explosive expulsion of overheated and compressed non equilibrium state of the surface melted material, and validate, as well, the high directionality of the plasma plume observed. (literal)

Note

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Dipartimento di Chimica, Università della Basilicata, Via N. Sauro 85, Potenza 85100, Italy CNR Istituto Meccanismi Inorganici e Plasmi, Sez. Potenza, Tito Scalo, Italy CNR Istituto per lo Studio dei Materiali Nanostrutturati, Sez. Roma1, Roma, Italy Metal and Ceramic Sciences Program, Ames Laboratory, Iowa State University, Ames, IA, USA (literal)

Titolo

Picosecond and femtosecond pulsed laser ablation and deposition of quasicrystals (literal)

Abstract

A Nd:glass laser with pulse duration of 250 fs and 1.3 ps has been used to evaporate a Al65Cu23Fe12 quasicrystalline target. The gaseous phase obtained from the ablation process has been characterised by several techniques such as emission spectroscopy, quadrupole mass spectrometry and ICCD imaging, used to study the plume composition, energy and morphology. The results show that the ablation processes in the short-pulse regimes are very different to the nanosecond one. In particular the plume angular distribution shows a characteristic high cosine exponent and the composition is completely stoichiometric and independent from the laser fluence. Furthermore the mass spectra indicate the presence of clusters, both neutral and ionised and the emission from the target suggest a rapid thermalisation leading to the melting of the surface. To clarify the ablation process some films have been deposited, on oriented silicon, at different experimental conditions and analysed by scanning electron microscopy, atomic force microscopy, energy dispersive X-ray analysis and X-ray diffraction. The analyses show the presence of nanostructured films retaining the target stoichiometry but consisting of different crystalline and non crystalline phases. In particular the nanostructure supports the hypothesis of the melting of the target during the ablation and a mechanism of material ejection is proposed for both picosecond and femtosecond regimes. (literal)

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