Ablation mechanism of PTFE under 157 nm irradiation
| Autor: | J. T. Dickinson, S. C. Langford, S. R. John |
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| Rok vydání: | 2008 |
| Předmět: | |
| Zdroj: | Applied Physics A. 92:981-985 |
| ISSN: | 1432-0630 0947-8396 |
| DOI: | 10.1007/s00339-008-4604-1 |
| Popis: | We report time- and mass-resolved measurements on neutral particles emitted from polytetrafluoroethylene (PTFE) during exposure to 157-nm laser radiation at fluences where etching is observed. By comparing the time-of-flight signals over a range of masses, we conclude that (CF2) N fragments for N=1–6 are emitted directly from the surface in substantial quantities. In contrast, the monomer (N=2) is the principal product during irradiation at 248 nm, where thermal decomposition is important. The time-of-flight signals of all the (CF2) N fragments show fast components with kinetic energies on the order of an electron volt. These high kinetic energies are consistent with photochemical scission of the polymer backbone, where a fraction of the excitation energy is delivered to the fragment as kinetic energy. Although clean etching is observed under these conditions, the great majority of the mass removed from the target appears as much larger fragments that do not reach our detector. The nature of this material and its affect on the velocity distribution of the observed (CF2) N fragments is discussed. |
| Databáze: | OpenAIRE |
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