On the role of chemical reactions in initiating ultraviolet laser ablation in poly(methyl methacrylate)

Manish Prasad, Patrick F. Conforti, Barbara Jane Garrison

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

The role of chemical reactions is investigated versus the thermal and mechanical processes occurring in a polymer substrate during irradiation by a laser pulse and subsequent ablation. Molecular dynamics simulations with an embedded Monte Carlo based reaction scheme were used to study ultraviolet ablation of poly(methyl methacrylate) at 157 nm. We discuss the onset of ablation, the mechanisms leading to ablation, and the role of stress relaxation of the polymer matrix during ablation. Laser induced heating and chemical decomposition of the polymer substrate are considered as ablation pathways. It is shown that heating the substrate can set off ablation via mechanical failure of the material only for very short laser pulses. For longer pulses, the mechanism of ejection is thermally driven limited by the critical number of bonds broken in the substrate. Alternatively, if the photon energy goes towards direct bond breaking, it initiates chemical reactions, polymer unzipping, and formation of gaseous products, leading to a nearly complete decomposition of the top layers of substrates. The ejection of small molecules has a hollowing out effect on the weakly connected substrates which can lead to lift-off of larger chunks. Excessive pressure buildup upon the creation of gaseous molecules does not lead to enhanced yield. The larger clusters are thermally ejected, and an entrainment of larger polymer fragments in gaseous molecules is not observed.

Original languageEnglish (US)
Article number103113
JournalJournal of Applied Physics
Volume101
Issue number10
DOIs
StatePublished - Jun 12 2007

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ultraviolet lasers
polymethyl methacrylate
laser ablation
ablation
chemical reactions
polymers
ejection
pulses
lasers
decomposition
molecules
heating
stress relaxation
entrainment
fragments
molecular dynamics
irradiation
photons
products
matrices

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

Cite this

Prasad, Manish ; Conforti, Patrick F. ; Garrison, Barbara Jane. / On the role of chemical reactions in initiating ultraviolet laser ablation in poly(methyl methacrylate). In: Journal of Applied Physics. 2007 ; Vol. 101, No. 10.
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On the role of chemical reactions in initiating ultraviolet laser ablation in poly(methyl methacrylate). / Prasad, Manish; Conforti, Patrick F.; Garrison, Barbara Jane.

In: Journal of Applied Physics, Vol. 101, No. 10, 103113, 12.06.2007.

Research output: Contribution to journalArticle

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