Mechanism of ultrashort laser ablation of metals: molecular dynamics simulation

Nedialkov, Nikolay N.; Imamova, S.E.; Atanasov, P.A.; Berger, Peter; Dausinger, Friedrich

doi:10.1016/j.apsusc.2005.01.056

Cited by 51 publications

(26 citation statements)

References 15 publications

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“…In fact, front-side spallation has recently been predicted by both hydrodynamic simulations, 24 MD modeling, 25 and combined two-temperature and MD modeling. 16,26 The picture is that the short pulse induces a strong pressure wave, which propagates into the material, and it is the combined effect of this pressure and the highly excited material, which leads to material fracture.…”

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confidence: 98%

Material swelling as the first step in the ablation of metals by ultrashort laser pulses

2011

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The ablation from a single-crystal Al(111) surface with single ultrashort near-infrared laser pulses has been investigated under ultrahigh vacuum conditions. Scanning-electron and atomic-force microscopy of the irradiated surface reveal a surprising development of the material response at increasing fluence: at low fluence, swelling exceeding one hundred nanometers dominates. At higher fluences, a hole is gradually formed in the swollen material, which eventually reaches below the original surface level. The observations indicate the significance of mechanical effects during ablation.Ultrashort-pulse excitation of solid materials has provided significant new information about the dynamics of highly excited matter. For instance, time-resolved x-ray diffraction experiments have shown how transient states of matter allow "ultrafast melting" of semiconductors (for a review, see Ref. 1). For metals, time-resolved electron diffraction experiments of thin aluminum foils have shown atomic disordering on a time scale of a few picoseconds. 2 The improved understanding of light-matter interaction has, ever since the first investigations of femtosecond-laser excitation, been paired with discussions about the possibilities of employing ultrashort-pulse laser excitation for precision manufacturing with minimized heat effects. [3][4][5][6] For further discussions about laser processing, please see Ref. 7.Ultrashort-pulse excitation of bulk metals is normally described using the two-temperature model, 8 which has provided a good explanation of observations in the low-fluence regime of relevance for surface-chemical reactions, 9 and with appropriate modifications also in the fluence regime of relevance for modifications of the native material, e.g., by laser ablation. [10][11][12][13][14][15] The precise response of the metal samples to the high excitation is a topic of ongoing discussion, see Ref. 16 and references therein. In a thermal description, the material is rapidly heated, leaving an overheated liquid, which cools adiabatically and is expelled by evaporation, spallation or-in case the thermodynamic path takes the system close to the critical point-by phase explosion.In this Brief Report, we report the surprising observation that the initial damage of a single-crystal metal surface induced by short-pulse excitation is not associated with significant material removal, rather with a pronounced swelling of the sample. As discussed in detail below, this observation is indicative of the strong mechanical effects that have been suggested to play a role during laser excitation. However, in contrast to predictions by molecular-dynamics simulations of the material response, significant material spallation does not set in immediately, rather a thick layer of material resolidifies in a foamy state with holes and voids, leaving a bump, which extends above the original surface level.Prior to any investigations of the single-crystal Al (111) surface, it is cleaned by a sputter gun with 1 keV Ar + ions for 60 minutes. The Ar atoms are...

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confidence: 98%

Material swelling as the first step in the ablation of metals by ultrashort laser pulses

2011

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“…27,[29][30][31] In either case, code writing is required in order to incorporate all the features of the analysis. The models presented in this article were realized through MATLAB.…”

Section: Simulation Methodologymentioning

confidence: 99%

“…28 The computational simplicity of MPF is an advantage that has been exploited by researchers, for the simulation of laser ablation. [29][30][31] With concern to researchers' studies on laser ablation aspects using the MPF, Cheng and Xu 29 investigated the disintegration mechanisms of Ni crystals during laser ablation, comparing and contrasting their differences according to the value of the laser energy. Nedialkov et al 30 developed a theoretical MD model and applied it on three different materials, namely, Al, Ni and Fe, in an attempt to determine laser ablation mechanisms with pulse duration.…”

Section: Simulation In Laser Ablationmentioning

confidence: 99%

Ablation study of laser micromachining process with molecular dynamics simulation

Markopoulos

Manolakos

2016

Proceedings of the Institution of Mechanical Engineers, Part B:

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A three-dimensional molecular dynamics model is presented for the simulation of the creation of a micro-hole on a thin film metal substrate via laser ablation. For the presented analysis, molybdenum and aluminium specimens are selected and short pulses are assumed. The laser fluence takes several values between 0.5 and 20 J/cm 2 . The proposed models include significant laser ablation phenomena such as plasma shielding. However, they are not computationally intense. In this study, the Morse potential is used for the interactions of the atoms of the specimens. The analysis is carried out in order to investigate the ablation rate, the ablation depth and the mean temperature of molybdenum and aluminium targets under their heating by the laser beam, for several different values of fluence. Results for molybdenum indicate that as fluence increases, it takes less time for the atoms to be ablated. For low-fluence pulses, more than one pulse may be required for the ablation of all atoms. For high-fluence pulses, the ablation is not uniform across the entire duration of the pulse and the specimen is overheated. A fluence value around 2-3 J/cm 2 is suggested for uniform ablation. From the analysis, it is evident that the evolution of ablation and system temperature is different for molybdenum and aluminium, for the same laser fluence. This is attributed to different crystalline structures and absorptivity of each material. It may be said that molecular dynamics prove to be a powerful tool for the simulation of nanomanufacturing processes and useful conclusions are drawn from the analysis.

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“…A lot of efforts have been devoted to the experimental and theoretical studies of the ultrashort laser-matter interactions in recent years, and numerical models based on comprehensive hydrodynamics [32][33][34][35] or molecular dynamics [23,[36][37][38][39][40][41][42][43] have been developed. Ultrashort laser ablation is a very complicated process, and further work is still needed to completely understand the fundamental ablation mechanisms.…”

Section: Ultrashort-pulsed Laser Ablationmentioning

confidence: 99%

“…Ultrashort laser ablation is a very complicated process, and further work is still needed to completely understand the fundamental ablation mechanisms. Earlier investigations show that material removal during ultrashort laser ablation may be realized through one or a combination of the following mechanisms, such as spallation, Coulomb explosion, phase explosion, critical-point phase separation (CPPS), and fragmentation [23,[33][34][35][36][37][38][39][40][41][42][43][44][45][46]. The actual mechanisms depend on laser intensity, wavelength, material types, etc.…”

Section: Ultrashort-pulsed Laser Ablationmentioning

confidence: 99%

Micro‐Laser Processing

Özel²

2011

Micro‐Manufacturing

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INTRODUCTIONThe use of laser technology in the processing of materials for micro-products has been reported over the last decade. Laser-based material processing on a microscale has been used in thermal processing, shock peening, surface treatment, cleaning of surfaces, welding, melting and polishing, scribing, as well as micromachining of basic geometric features on a variety of materials [1][2][3][4][5][6][7][8][9][10][11][12].Lasers are usually categorized as two groups: continuous wave (cw) and pulsed lasers. Conventional cw and pulsed laser irradiation and ablation is used in many fields, such as material processing, machining, etching, deposition, sintering, micro-fluidics, medical, and many other applications [13][14][15][16][17][18][19].The use of lasers in micro-manufacturing is closely connected to the characteristics of the laser. The main laser parameters to be chosen and controlled are wavelength, λ (nm); average power (W) or energy (J); intensity (W/m 2 ) or fluence, ( ) (J/m 2 ); pulse duration, τ (s); pulse repetition rates (Hz); and peak power (pulse energy/pulse duration) [9,11,16,20,21].Pulsed lasers achieve much higher intensities than cw lasers and are the preferred solution for the fabrication of micro-sized structures. Long-pulsed (nanosecond, ns), short-pulsed (picoseconds, ps), and ultrashort-pulsed (femtosecond, fs) lasers that are commonly used for repairing, trimming, marking, scribing, texturing, welding, ablation, cutting, and drilling include among others (i) Excimer lasers with ultraviolet (UV) wavelengths, (ii) Ti:sapphire lasers Micro-Manufacturing: Design and Manufacturing of Micro-Products, First Edition. Edited by Muammer Koç and TugrulÖzel.

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Mechanism of ultrashort laser ablation of metals: molecular dynamics simulation

Cited by 51 publications

References 15 publications

Material swelling as the first step in the ablation of metals by ultrashort laser pulses

Material swelling as the first step in the ablation of metals by ultrashort laser pulses

Ablation study of laser micromachining process with molecular dynamics simulation

Micro‐Laser Processing

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