Laser-pulse sputtering of aluminium: gas-dynamic effects with recondensation and reflection conditions at the Knudsen layer

Miotello, A.; Peterlongo, Andrea; Kelly, Roger

doi:10.1016/0168-583x(95)00294-4

Cited by 13 publications

(6 citation statements)

References 12 publications

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“…The back condensation of the vapour was supposed to start after laser pulse termination when the target surface had cooled. Laser ablation models [8,9] were proposed where the targetvapour interface was not considered as a rigid wall when evaporation was over, but where the vapour was allowed to condense back on the target.…”

Section: Introductionmentioning

confidence: 99%

Near-surface laser–vapour coupling in nanosecond pulsed laser ablation

Gusarov

Smurov

2003

J. Phys. D: Appl. Phys.

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The evaporation mechanism at high temperatures is one of the disputable points of the conventional thermal model of laser ablation connecting heat transfer in the target with gas-phase dynamics. A model of supercritical ablation is proposed where the vapour density is limited by a transparency condition. The model is basically laser-vapour coupling in a thin near-surface layer. The experiments on ablation of Au at 193 and 266 nm, Al at 266 nm, and graphite at 1.06 µm can be described by the proposed model. However, optical breakdown is important in graphite ablation at 193 and 248 nm. When the target surface temperature is less than the critical one (typically at fluences less than or about several J cm −2 ) the thermal evaporation mechanism works. At higher laser fluences it has been found that a combination of the proposed supercritical ablation mechanism with optical breakdown in the volume of the gas phase is more realistic.

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Section: Introductionmentioning

confidence: 99%

Near-surface laser–vapour coupling in nanosecond pulsed laser ablation

Gusarov

Smurov

2003

J. Phys. D: Appl. Phys.

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“…There exists extensive literature on Knudsen layer modeling, at various scales and levels of detail [51][52][53][54][55][56][57]. A useful treatment was given by Knight [52], whose relations account for evaporation into a background gas.…”

Section: Knudsen Layermentioning

confidence: 99%

A multiphase model for pulsed ns-laser ablation of copper in an ambient gas

Autrique

Chen

Alexiades

et al. 2012

AIP Conference Proceedings

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Laser ablation in an ambient gas is nowadays used in a growing number of applications, such as chemical analysis and pulsed laser deposition. Despite the many applications, the technique is still poorly understood. Therefore models describing the material evolution in time during short pulse laser irradiation can be helpful to unravel the puzzle and finally result in the optimization of the related applications. In the present work, a copper target is immersed in helium, initially set at atmospheric pressure and room temperature. Calculations are performed for a Gaussian-shaped laser pulse with a wavelength of 532 nm, full width at half maximum of 6 ns, and laser fluences up to 10 J/cm 2 .In order to describe the transient behaviour in and above the copper target, hydrodynamic equations are solved. An internal energy method accounting for pressure relaxation is applied for the description of the target. In the plume domain a set of conservation equations is solved,assuming local thermodynamic equilibrium. Calculated crater depths and transmission profiles are compared with experimental results and similar trends are found. Our calculations indicate that for the laser fluence regime under study, explosive boiling could play a fundamental role in the plasma formation of metals under ns-pulsed laser irradiation.

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“…The physical interpretation of experimental data including various discontinuities is, however, not yet clear. The results given by a number of analytical and numerical models [5][6][7][8][9][10][11][12] may strongly differ because of different boundary conditions applied at the evaporated surface: a hard wall (plane of symmetry) boundary condition was used in [5,6]. The authors of [5] specified initial vapour cloud parameters, which were estimated from experiment.…”

Section: Introductionmentioning

confidence: 99%

“…Conventional gas-dynamic methods are not sufficient in this case because a significant non-equilibrium exists in the region adjacent to the surface, the Knudsen layer. A quasi-steady approach to the Knudsen layer was applied in [7][8][9][10][11][12] to derive gas-dynamic boundary conditions. The methods of Mott-Smith [7] and of the formal solution of a relaxation equation [8] gave very similar results.…”

Section: Introductionmentioning

confidence: 99%

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Target-vapour interaction and atomic collisions in pulsed laser ablation

Gusarov

Smurov

2001

J. Phys. D: Appl. Phys.

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Numerical solution of the Boltzmann equation with a relaxation collision term is used to study gas-dynamic flows formed under nanosecond pulsed laser ablation. Atoms ejected from the surface of a target are assumed to have a Maxwell velocity distribution corresponding to the surface temperature and the saturated vapour pressure. The surface temperature is obtained from a transient heat transfer equation in the condensed phase. Atomic collisions in the ablation plume orient atoms towards the surface normal and speed up the plume expansion from the target. Atoms backscattered in the gas phase, stick to the target surface and cause back condensation of the vapour at later stages. When the mean free path is much less than the plume dimension, a Knudsen layer, a hydrodynamic flow region, and a low-density tail may be distinguished in the gas phase. The present numerical simulation is in good agreement with the analytical quasi-steady Mott-Smith approach to the Knudsen layer in the case of evaporation and at the early stages of condensation. Comparison with experiment reveals that the model underestimates both the width of the ablated material angular distribution and the amount of high-energy atoms. The difference increases with the laser fluence and may be caused by lateral expansion of the plume, by vapour acceleration due to laser radiation absorption or probably by non-thermal evaporation effects.

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Laser-pulse sputtering of aluminium: gas-dynamic effects with recondensation and reflection conditions at the Knudsen layer

Cited by 13 publications

References 12 publications

Near-surface laser–vapour coupling in nanosecond pulsed laser ablation

Near-surface laser–vapour coupling in nanosecond pulsed laser ablation

A multiphase model for pulsed ns-laser ablation of copper in an ambient gas

Target-vapour interaction and atomic collisions in pulsed laser ablation

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