Numerical simulation of ultrafast expansion as the driving mechanism for confined laser ablation with ultra-short laser pulses

Sotrop, Jürgen; Kersch, Alfred; Domke, Matthias; Heise, G.; Huber, Heinz P.

doi:10.1007/s00339-013-7849-2

Cited by 51 publications

(18 citation statements)

References 36 publications

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“…While the release mechanism responsible for LIBT is not the main focus of this work, contributing processes are suspected to be either thermal [18], shock induced via spallation [19], through the vaporization of carrier or donor volumes to enable a vapour-driven release of the deposit [20], or via ultrafast expansion if using femtosecond laser pulses [21]. Although we have not yet looked at LIBT with other laser sources (e.g.…”

Section: Introductionmentioning

confidence: 99%

Laser-induced backward transfer of nanoimprinted polymer elements

et al. 2016

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Femtosecond laser-induced backward transfer of transparent photopolymers is demonstrated in the solid state, assisted by a digital micromirror spatial light modulator for producing shaped deposits. Through use of an absorbing silicon carrier substrate, we have been able to successfully transfer solid-phase material, with lateral dimensions as small as *6 lm. In addition, a carrier of silicon incorporating a photonic waveguide relief structure enables the transfer of imprinted deposits that have been accomplished with surface features exactly complementing those present on the substrate, with an observed minimum feature size of 140 nm.

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Section: Introductionmentioning

confidence: 99%

Laser-induced backward transfer of nanoimprinted polymer elements

et al. 2016

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“…39,40 Heating causes material expansion and further phase transitions, e.g., a phase explosion when evaporation is involved at fluences well above the ablation threshold. The phase explosion creates a gas-liquid mixture that scatters and absorbs the reflected light.…”

Section: Discussionmentioning

confidence: 99%

Physical mechanisms of SiNx layer structuring with ultrafast lasers by direct and confined laser ablation

Rapp

Heinrich

Wollgarten

et al. 2015

Journal of Applied Physics

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In the production process of silicon microelectronic devices and high efficiency silicon solar cells, local contact openings in thin dielectric layers are required. Instead of photolithography, these openings can be selectively structured with ultra-short laser pulses by confined laser ablation in a fast and efficient lift off production step. Thereby, the ultrafast laser pulse is transmitted by the dielectric layer and absorbed at the substrate surface leading to a selective layer removal in the nanosecond time domain. Thermal damage in the substrate due to absorption is an unwanted side effect. The aim of this work is to obtain a deeper understanding of the physical laser-material interaction with the goal of finding a damage-free ablation mechanism. For this, thin silicon nitride (SiN x ) layers on planar silicon (Si) wafers are processed with infrared fs-laser pulses. Two ablation types can be distinguished: The known confined ablation at fluences below 300 mJ/cm 2 and a combined partial confined and partial direct ablation at higher fluences. The partial direct ablation process is caused by nonlinear absorption in the SiN x layer in the center of the applied Gaussian shaped laser pulses. Pump-probe investigations of the central area show ultra-fast reflectivity changes typical for direct laser ablation. Transmission electron microscopy results demonstrate that the Si surface under the remaining SiN x island is not damaged by the laser ablation process. At optimized process parameters, the method of direct laser ablation could be a good candidate for damage-free selective structuring of dielectric layers on absorbing substrates. V C 2015 AIP Publishing LLC.

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“…The physical understanding of the effect of the spatial confinement on laser-induced processes is largely based on the results of theoretical analysis of the evolution of pressure generated under conditions of spatially-confined laser ablation [216,223] and continuum-level modeling of thermo-elastic deformation of metal films irradiated through transparent substrates [218,226,227]. These studies have recently been complemented by atomistic molecular dynamics (MD) simulations of short pulse laser interactions with bulk metal substrate covered by a transparent overlayer [56].…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…In several recent numerical simulations of thin film removal by backside femtosecond pulse irradiation through a transparent substrate, the dynamics of the relaxation of thermo-elastic stresses and the mechanical deformation of the metal film are considered [218,226,227] and found to play the dominant role in the separation and ejection of the film fragments at laser fluences close to the ablation threshold [226]. The analysis of the effect of the spatial confinement on the kinetics and mechanisms of laser-induced phase transformation, as well as the structural modification of the metal target, however, is beyond the capabilities of the continuum-level finite difference [227] or finite element method [218,226] calculations. On the other hand, the atomistic molecular dynamics (MD) simulations, while more computationally expensive, have been shown to be capable of providing detailed information on the fast non-equilibrium structural and phase transformations induced by short pulse laser irradiation of thin films [228-231, 152, 161, 162] and bulk targets [24,113,120,129,134,146,152,232,233] under vacuum conditions or in the presence of background gas [234].…”

Section: Introductionmentioning

confidence: 99%

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Atomistic Simulation Study of Short Pulse Laser-Induced Generation of Crystal Defects in Metal Targets

Karim

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AUTHORThe dissertation has been read and approved by the examining committee: Computational analysis reveals a strong correlation between the solidification front velocity and the concentration of vacancies, which in turn suggests that the vacancies are mainly generated at the rapidly advancing solidification front under conditions of strong undercooling below the melting temperature of the target material.The laser-induced generation of dislocations is also observed in the simulations of bcc Cr targets and is found to have a strong dependence on the crystallographic orientation of the target surface. For (001) Cr targets, a transient appearance of small loops of unstable partial dislocations outlining islands of stacking faults takes place at the initial stage of the relaxation of laser-induced stresses. For (110) and (111) Cr targets, the emission of a high density of perfect dislocations from the melting front is observed a few picoseconds after the laser pulse and is related to the high values of the resolved shear stress generated in many of the 48 slip systems of the bcc structure.The computational predictions from this study have implications for optimization of the experimental conditions in current and emerging applications based on short pulse laser-induced surface modification. VIII

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Numerical simulation of ultrafast expansion as the driving mechanism for confined laser ablation with ultra-short laser pulses

Cited by 51 publications

References 36 publications

Laser-induced backward transfer of nanoimprinted polymer elements

Laser-induced backward transfer of nanoimprinted polymer elements

Physical mechanisms of SiNx layer structuring with ultrafast lasers by direct and confined laser ablation

Atomistic Simulation Study of Short Pulse Laser-Induced Generation of Crystal Defects in Metal Targets

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