Accumulation effects in laser ablation of metals with high-repetition-rate lasers

Račiukaitis, Gediminas; Brikas, Marijus; Gečys, Paulius; Gedvilas, Mindaugas

doi:10.1117/12.782937

Cited by 103 publications

(67 citation statements)

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“…9a, These nanograins can also be considered as having fcc structure with a high density of aligned stacking faults, with stacking faults present on every other plane within the hcp regions. Some of the nanograins exhibit an apparently random mixture of fcc-and hcp-like stacking of closepacked planes that has been observed experimentally in hard-sphere colloidal crystals [70][71][72] and atomistic simulations [73][74][75]. The coexistence of fcc and hcp grains has been observed in pulsed laser deposited nanocrystalline Ni films [77], where the formation of stacking faults on in-plain {111} fcc faces in the process of film deposition is considered to be the mechanism leading to the formation of hcp grains.…”

Section: Structure Of the Nanocrystalline Surface Layermentioning

confidence: 82%

“…This observation may be related to the incubation effect reported for multi-pulse irradiation of metal targets, when the laser fluence threshold for ablation/damage decreases with increasing number of laser pulses applied to the same area, e.g., [61,[65][66][67][68][69]. While the generation and accumulation of defects has been discussed in general terms as one of the mechanisms [12,[65][66][67]70] (along with the absorption enhancement due to roughening of the surface [61,68] and heat accumulation in high repetition rate irradiation [70]) responsible for the incubation effect, the current simulation results provide first direct insights into the laser-induced structural-modification processes that will also contribute to the reduction of the spallation threshold in the multi-pulse laser irradiation regime.…”

Section: Spallation By 2 Nd Pulse: Connection To Incubation Effectmentioning

confidence: 96%

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Generation of subsurface voids and a nanocrystalline surface layer in femtosecond laser irradiation of a single-crystal Ag target

et al. 2015

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Structural transformations in a shallow surface region of a bulk Ag (001) target irradiated by a femtosecond laser pulse are investigated in large-scale atomistic simulations and experiments.The simulations reveal a complex interplay of fast laser melting, rapid resolidification, and the dynamic relaxation of laser-induced stresses that leads to the formation of a sub-surface porous region covered by a nanocrystalline surface layer. The generation of the porous region is consistent with the experimental observation of surface "swelling" occurring at laser fluences below the spallation/ablation threshold and may be related to the incubation effect in multi-pulse laser ablation of metals. The nanocrystalline layer is produced by massive nucleation of crystallites triggered by a deep undercooling of the melted surface region experiencing fast quenching at a rate on the order of 10 11 K/s. The predicted surface structure features random crystallographic orientation of nanograins and a high density of stacking faults, twins, and nanoscale twinned structural elements with five-fold symmetry, which suggests high hardness and possible enhancement of catalytic activity of the surface.

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Section: Structure Of the Nanocrystalline Surface Layermentioning

confidence: 82%

Section: Spallation By 2 Nd Pulse: Connection To Incubation Effectmentioning

confidence: 96%

Generation of subsurface voids and a nanocrystalline surface layer in femtosecond laser irradiation of a single-crystal Ag target

et al. 2015

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“…The generation of crystal defects may be, thus, related to the incubation effect, when the laser fluence threshold for ablation/damage decreases significantly with increasing number of laser pulses applied to the same area, e.g., [145][146][147][148][149]. The high density of vacancies generated in the surface region should also play an important role in the redistribution of impurities or mixing/alloying in multicomponent or composite targets.…”

Section: Generation Of Crystal Defectsmentioning

confidence: 99%

Atomic/Molecular-Level Simulations of Laser–Materials Interactions

Zhigilei

Lin

Ivanov

et al. 2009

Laser-Surface Interactions for New Materials Production

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Summary. Molecular/atomic-level computer modeling of laser-materials interactions is playing an increasingly important role in the investigation of complex and highly nonequilibrium processes involved in short-pulse laser processing and surface modification. This chapter provides an overview of recent progress in the development of computational methods for simulation of laser interactions with organic materials and metals. The capabilities, advantages, and limitations of the molecular dynamics simulation technique are discussed and illustrated by representative examples. The results obtained in the investigations of the laser-induced generation and accumulation of crystal defects, mechanisms of laser melting, photomechanical effects and spallation, as well as phase explosion and massive material removal from the target (ablation) are outlined and related to the irradiation conditions and properties of the target material. The implications of the computational predictions for practical applications, as well as for the theoretical description of the laser-induced processes are discussed. IntroductionShort-pulse lasers are used in a diverse range of applications, from advanced materials processing, cutting, drilling, and surface micro-and nanostructuring [1,2] to pulsed-laser deposition of thin films and coatings [3], laser surgery [4,5], and artwork restoration [6,7], and to the exploration of the conditions for inertial confinement fusion, with the world's most energetic laser system being built at the National Ignition Facility at Lawrence Livermore National Laboratory [8]. At the fundamental science level, short-pulse laser irradiation has the ability to bring material into a highly nonequilibrium state and provides a unique opportunity to probe the material behavior under extreme conditions. In particular, optical pump-probe experiments have been used to investigate transient changes in the electronic structure of the irradiated surface with high (often subpicosecond) temporal resolution [9][10][11][12][13], whereas recent advances in time-resolved X-ray and electron diffraction

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“…Specifically, according to the incubation model of Jee et al [16], the multi-shot ablation fluence threshold F N is related to the single-pulse ablation threshold fluence F 1 by a power law, F N = F 1 N S−1 , where N is the number of accumulated laser pulses and S is the accumulation parameter. The value of S for stainless steel in a femtosecond laser system obtained from the experiments is 0.86 [17], resulting, for N ≈ 1300 at the given scanning speed, in an effective fragmentation threshold fluence F frag,N ≈ 0.20 J/cm 2 , which is exceeded in the trench centers for a peak incident fluence F ≈ 0.23 J/cm 2 . The employed cumulative ablation provided by the total exposure per spot of ∼300 J/cm 2 , i.e., almost by an order of magnitude in comparison with ∼2200 J/cm 2 in the previous study [2], yielded a contact angle of 145 • for the texture with microcone surface asperities of similar size.…”

Section: Resultsmentioning

confidence: 99%

Fabrication of Superhydrophobic Coating on Stainless Steel Surface by Femtosecond Laser Texturing and Chemisorption of an Hydrophobic Agent

et al. 2015

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Accumulation effects in laser ablation of metals with high-repetition-rate lasers

Cited by 103 publications

References 0 publications

Generation of subsurface voids and a nanocrystalline surface layer in femtosecond laser irradiation of a single-crystal Ag target

Generation of subsurface voids and a nanocrystalline surface layer in femtosecond laser irradiation of a single-crystal Ag target

Atomic/Molecular-Level Simulations of Laser–Materials Interactions

Fabrication of Superhydrophobic Coating on Stainless Steel Surface by Femtosecond Laser Texturing and Chemisorption of an Hydrophobic Agent

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