The role of electron–phonon coupling in femtosecond laser damage of metals

Wellershoff, S.-S.; Hohlfeld, J.; Güdde, J.; Matthias, E.

doi:10.1007/s003399900305

Cited by 199 publications

(192 citation statements)

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“…It was further observed that the threshold fluence does not depend on the pulse duration below 100 ps pulses [63]. However, the metal sample thickness plays an important role [64][65][66]. Threshold fluence increases with increasing sample thickness for metal samples thinner than the hot electron diffusion length (Lc) of the respective metal.…”

Section: Ablation Thresholdmentioning

confidence: 99%

“…Once the sample thickness is larger than Lc, threshold fluence does not vary with thickness anymore, and the fluence is said to be at saturation. Thus, for Au the threshold fluence does not change if the sample is thicker than 800 nm, and for Ni saturation is reached at 50 nm [64]. Yahng et al (2009) studied the effect of the sample temperature on threshold fluence and found that for Si the threshold fluence decreases with increasing temperature from 300 to 900 K, whereas for SS304 no change in ablation threshold was found, but the ablation efficiency increased by 20% [67].…”

Section: Ablation Thresholdmentioning

confidence: 99%

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Fabrication of Micro/Nano Structures on Metals by Femtosecond Laser Micromachining

2014

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Abstract:Femtosecond laser micromachining has emerged in recent years as a new technique for micro/nano structure fabrication because of its applicability to virtually all kinds of materials in an easy one-step process that is scalable. In the past, much research on femtosecond laser micromachining was carried out to understand the complex ablation mechanism, whereas recent works are mostly concerned with the fabrication of surface structures because of their numerous possible applications. The state-of-the-art knowledge on the fabrication of these structures on metals with direct femtosecond laser micromachining is reviewed in this article. The effect of various parameters, such as fluence, number of pulses, laser beam polarization, wavelength, incident angle, scan velocity, number of scans, and environment, on the formation of different structures is discussed in detail wherever possible. Furthermore, a guideline for surface structures optimization is provided. The authors' experimental work on laser-inscribed regular pattern fabrication is presented to give a complete picture of micromachining processes. Finally, possible applications of laser-machined surface structures in different fields are briefly reviewed.

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Section: Ablation Thresholdmentioning

confidence: 99%

Section: Ablation Thresholdmentioning

confidence: 99%

Fabrication of Micro/Nano Structures on Metals by Femtosecond Laser Micromachining

2014

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“…The electron-phonon relaxation time of Ni is ep Ϸ 6-7 ps. 9,35 By energy balance considerations, the average energy per particle p can be estimated as…”

Section: B Np Plumementioning

confidence: 99%

Dynamics of the plumes produced by ultrafast laser ablation of metals

Donnelly¹,

Lunney²,

Amoruso³

et al. 2010

Journal of Applied Physics

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We have analyzed ultrafast laser ablation of a metallic target ͑Nickel͒ in high vacuum addressing both expansion dynamics of the various plume components ͑ionic and nanoparticle͒ and basic properties of the ultrafast laser ablation process. While the ion temporal profile and ion angular distribution were analyzed by means of Langmuir ion probe technique, the angular distribution of the nanoparticulate component was characterized by measuring the thickness map of deposition on a transparent substrate. The amount of ablated material per pulse was found by applying scanning white light interferometry to craters produced on a stationary target. We have also compared the angular distribution of both the ionic and nanoparticle components with the Anisimov model. While the agreement for the ion angular distribution is very good at any laser fluence ͑from ablation threshold up to Ϸ1 J/ cm 2 ͒, some discrepancies of nanoparticle plume angular distribution at fluencies above Ϸ0.4 J / cm 2 are interpreted in terms of the influence of the pressure exerted by the nascent atomic plasma plume on the initial hydrodynamic evolution of the nanoparticle component. Finally, analyses of the fluence threshold and maximum ablation depth were also carried out, and compared to predictions of theoretical models. Our results indicate that the absorbed energy is spread over a length comparable with the electron diffusion depth L c ͑Ϸ30 nm͒ of Ni on the timescale of electron-phonon equilibration and that a logarithmic dependence is well-suited for the description of the variation in the ablation depth on laser fluence in the investigated range.

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“…Le faisceau est focalise sur l'echantillon par une lentille de 50 mm de focale. Une des raisons pouvant expliquer la difference d'efficacite pour les memes conditions experimentales dans le cas du cuivre et de I'inox est la difference de comportement electronique du fait du couplage electron-phonon [1,2]. Ce couplage etant plus important pour I'inox que pour le cuivre, les electrons thermiques diffusent moins dans I'inox que dans le cuivre, la zone adressee par le rayonnement puis ablatee est done plus grande dans le cuivre que dans I'inox.…”

Section: Dispositif Experimentalunclassified