Laser-induced decomposition and ablation dynamics studied by nanosecond interferometry - 3. A polyurethane film

Citation
T. Masubuchi et al., Laser-induced decomposition and ablation dynamics studied by nanosecond interferometry - 3. A polyurethane film, J PHOTOCH A, 145(3), 2001, pp. 215-222
Citations number
33
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY
ISSN journal
1010-6030 → ACNP
Volume
145
Issue
3
Year of publication
2001
Pages
215 - 222
Database
ISI
SICI code
1010-6030(200112)145:3<215:LDAADS>2.0.ZU;2-Y
Abstract
A polyurethane sample film was prepared by adding phenol resin as a structu ral stabilizer and its laser ablation dynamics was studied upon excimer las er irradiation. The ablation threshold by 248 rum excitation was determined to be 40 mJ/cm(2) and no appreciable debris was left. The etch depth incre ases with the fluence and reaches 0.5 mum at the fluence of 1 J/cm(2). Time -resolved interferometric images were measured in the nanosecond to microse cond time region under surface and internal optical alignments. The film wa s decomposed efficiently into debris, fragments, aggregates, and so on whic h are smaller than the wavelength, as observed images were not disturbed by the decomposed products. At the fluence of 310 mJ/cm(2), etching proceeds fast during the initial half of the excitation laser pulse, but stopped at the late stage of the pulse. The direct measurement of transient absorbance change at 248 nm explains that ejected products still absorb the excitatio n photons and interrupt a further etching. Laser-induced expansion was not observed above the ablation threshold, while below the value an expansion f orms a bump and followed by rapid contraction. The morphological behavior i s quite different from that of usual photothermal expansion and contraction dynamics observed for poly(methyl methacrylate) and polystyrene, hence it is considered that laser ablation is induced photochemically. (C) 2001 Else vier Science B.V. All rights reserved.