Effects of pulse duration on the ns-laser pulse induced removal of thin film materials used in photovoltaics

Bovatsek, Jim; Tamhankar, Ashwini; Patel, Raj; Bulgakova, Nadezhda M.

doi:10.1117/12.809842

Cited by 21 publications

(9 citation statements)

References 2 publications

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“…However, in the first order approximation, the melting threshold is independent of laser pulse duration due to relatively small heat penetration depth. 33 In Table I we list measured and numerically predicted melting thresholds for above given metals along with their handbooks values of Poisson's ratios. 34 Experimentally measured melting thresholds (I exp melt ) were obtained using polynomial fit intersections between the horizontal baseline (i.e.…”

Section: Resultsmentioning

confidence: 99%

Examination of nanosecond laser melting thresholds in refractory metals by shear wave acoustics

et al. 2017

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Nanosecond laser pulse-induced melting thresholds in refractory (Nb, Mo, Ta and W) metals are measured using detected laser-generated acoustic shear waves. Obtained melting threshold values were found to be scaled with corresponding melting point temperatures of investigated materials displaying dissimilar shearing behavior. The experiments were conducted with motorized control of the incident laser pulse energies with small and uniform energy increments to reach high measurement accuracy and real-time monitoring of the epicentral acoustic waveforms from the opposite side of irradiated sample plates. Measured results were found to be in good agreement with numerical finite element model solving coupled elastodynamic and thermal conduction governing equations on structured quadrilateral mesh. Solid-melt phase transition was handled by means of apparent heat capacity method. The onset of melting was attributed to vanished shear modulus and rapid radial molten pool propagation within laser-heated metal leading to preferential generation of transverse acoustic waves from sources surrounding the molten mass resulting in the delay of shear wave transit times. Developed laser-based technique aims for applications involving remote examination of rapid melting processes of materials present in harsh environment (e.g. spent nuclear fuels) with high spatio-temporal resolution.

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Section: Resultsmentioning

confidence: 99%

Examination of nanosecond laser melting thresholds in refractory metals by shear wave acoustics

et al. 2017

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“…Bulgakova et al simulated vaporization for fluences up to the onset of phase explosion [17,18], considering surface reflection as temperature dependent. Bovatsek et al then applied this model to heat transfer in thin multilayer materials [19], considering one-dimensional heat flow throughout the thickness. Pomeala and Willis explored the effects of dielectric transition on threshold fluence [20], considering thermal conductivity as constant and using a simple optical model.…”

Section: Introductionmentioning

confidence: 99%

Modeling of Thin-Film Single and Multilayer Nanosecond Pulsed Laser Processing

Lutey

2013

Journal of Manufacturing Science and Engineering

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A complete model of nanosecond pulsed laser scribing of arbitrary thin multilayer structures is presented. The chain of events is separated according to time-scale; an initial simulation considers material response during the pulse; another combines this result with the much slower effects of heat flow away from the laser axis. The former considers heating, vaporization and phase explosion of metals in the course of a single pulse, accounting for variations in thermal conductivity and optical absorption as the material becomes superheated and approaches its critical temperature. The latter calculates the bidimensional heat flow in a complete multilayer structure over the course of a scribing operation, combining material properties and considering removal by both short-pulse ablation and long-term heating of the workpiece. Simulation results for the single pulse ablation of an aluminum target align well with published experimental data both in terms of phase-explosion threshold and ablation depth as a function offluence. Bidinierrsional heat flow simulations of a polypropylene-aluminum-polypropylene triplex structure reveal the progression of events toward steady state behavior; aluminum ejected due to short-pulse ablation and plastic removed due to conduction.

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“…The Alpine project aims to achieve excellent scribing patterning on CdTe and CIGS modules by means of high performance fiber lasers. Several works on lasers scribing solutions for solar cells exist [4,5] but generally face some limitations [6] that are related to long pulses duration. This is a general concern today in solar cells industry to have a high speed and precision process without important induced damages.…”

Section: Introductionmentioning

confidence: 99%