Mechanisms of melt droplets and solid-particle ejection from a target surface by pulsed laser action

Brailovsky, A. B.; Gaponov, S. V.; Luchin, V. I.

doi:10.1007/bf01538216

Cited by 112 publications

(42 citation statements)

References 11 publications

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“…The nonuniform surface evaporation in turn could induce local pressure gradients in the plasma developing in front of the irradiated target. 26,28 This pressure is higher around the columns than on their top, inducing liquid motion upwards and contributing to the initial columns formation. With further irradiation, the column diameters remain practically unchanged [compare Figs.…”

Section: Discussionmentioning

confidence: 99%

Microcolumn development on titanium by multipulse laser irradiation in nitrogen

et al. 2003

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We report the growth of titanium nitride microcolumns under multipulse Nd:yttrium aluminum garnet ( ‫ס‬ 1.064 m, ∼ 300 ns, ‫ס‬ 30 kHz) laser irradiation of titanium targets in nitrogen atmosphere. The laser intensity value was chosen below the single-pulse melting threshold of titanium. The evolution with the number of laser pulses of the target morphology, crystalline state, and chemical composition at the surface as well as in depth were investigated by scanning electron microscopy, x-ray diffractometry, Raman spectroscopy, and wavelength dispersive x-ray spectroscopy. Under the action of the laser pulses, during progressive surface nitridation, an initial rippled morphology developed, which evolved with further irradiation to TiN microcolumns. In-depth investigations showed a granular zone beneath the surface consisting of rutile and anatase phase TiO 2 , followed by a compact needlelike layer of titanium until the interface with the unaffected target material.

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Section: Discussionmentioning

confidence: 99%

Microcolumn development on titanium by multipulse laser irradiation in nitrogen

et al. 2003

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“…Evaporation and thermal conduction to the bulk of the target can lead to solidification of the asperities. These processes could be responsible for the formation of hydrodynamic patterns/asperities observed experimentally for metal targets, where thermal conduction is sufficient to provide fast cooling and freezing of the transient liquid surface features [16,22,23]. Note that the ejection of large droplets due to the hydrodynamic effects occurring on the scale of the whole laser spot cannot be investigated by the MD simulation technique and is beyond the scope of the present paper.…”

Section: 3mentioning

confidence: 96%

“…The term hydrodynamic sputtering is typically used to refer to a range of processes in which large droplets are ejected as a result of a transient melting and motion of a liquid caused by steep thermal gradients and relaxation of the laserinduced pressure [15,16,22,33]. Formation of hydrodynamic instabilities in a single-shot ablation [16,23] as well as the appearance, gradual growth, and eventual separation of molten asperities due to the combined action of inertial and surface tension forces in a multi-pulse irradiation regime [16,22,33] have been discussed.…”

Section: 3mentioning

confidence: 99%

“…Formation of hydrodynamic instabilities in a single-shot ablation [16,23] as well as the appearance, gradual growth, and eventual separation of molten asperities due to the combined action of inertial and surface tension forces in a multi-pulse irradiation regime [16,22,33] have been discussed. Analysis of surface morphology of irradiated targets provides strong support for the hydrodynamic mechanism of large-droplet ejection in metals [16,22,23]. …”

Section: 3mentioning

confidence: 99%

“…The implications of cluster ejection for practical applications have motivated a number of experimental and theoretical investigations aimed specifically at understanding the conditions and mechanisms of cluster production in laser ablation [6,[13][14][15][16][17][18][19]. For organic targets, cluster-size distributions have been studied in trapping plate experiments performed by Handschuh et al [13] for ultra-violet (UV)-MALDI conditions, laser-induced thermal desorption, and infra-red (IR) polymer ablation.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of the plume formation and parameters of the ejected clusters in short-pulse laser ablation

Zhigilei

2003

Applied Physics A: Materials Science & Processing

292

197

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The dynamics of the early stages of the ablation plume formation and the mechanisms of cluster ejection are investigated in large-scale molecular dynamics simulations. The cluster composition of the ablation plume has a strong dependence on the irradiation conditions and is defined by the interplay of a number of processes during the ablation plume evolution. At sufficiently high laser fluences, the phase explosion of the overheated material leads to the formation of a foamy transient structure of interconnected liquid regions that subsequently decomposes into a mixture of liquid droplets, gasphase molecules, and small clusters. The ejection of the largest droplets is attributed to the hydrodynamic motion in the vicinity of the melted surface, especially active in the regime of stress confinement. Spatially resolved analysis of the dynamics of the plume formation reveals the effect of segregation of the clusters of different sizes in the expanding plume. A relatively low density of small/medium clusters is observed in the region adjacent to the surface, where large clusters are being formed. Medium-size clusters dominate in the middle of the plume and only small clusters and monomers are observed near the front of the expanding plume. Despite being ejected from deeper under the surface, the larger clusters in the plume have substantially higher internal temperatures as compared to the smaller clusters. The cluster-size distributions can be relatively well described by a power law Y(N) ∼ N −τ with exponents different for small, up to ∼ 15 molecules, and large clusters. The decay is much slower in the high-mass region of the distribution.

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