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Proceedings Paper

Time-of-flight mass spectroscopy of femtosecond laser ablation of solid surfaces
Author(s): Andrea Cavalleri; Klaus Sokolowski-Tinten; Joerg Bialkowski; Dietrich von der Linde
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Paper Abstract

We have investigated femtosecond laser-induced ablation of gallium arsenide and silicon using time-of-flight mass spectroscopy. Below the ablation threshold we observe free flight desorption of atoms from the laster heated surface. The absence of collisions between particles leaving the solid allows to obtain the maximum surface temperature during laser irradiation of Gallium Arsenide. We estimated maximum surface temperatures of the order of 3500 K at the ablation threshold, where we observed a step-like increase in the number of detected particles. In the case of Silicon the existence of molecules of up to 6 atoms does not allow to measure the surface temperature. With increasing fluence free flight desorption transforms into a collisional expansion process. The behavior of Gallium particles can be quantitatively described through Knudsen-layer theory, indicating that Gallium particles expand as a non-ideal gas close to the ablation threshold ((gamma) equals Cv/Cp less than 5/3). Above fluences of approximately 2.5 Fth (gamma) approaches 5/3 indicating an ideal gas behavior for the expanding material. Dilution into the two phase regime of a superheated liquid characterizes ablation close to threshold.

Paper Details

Date Published: 14 September 1998
PDF: 10 pages
Proc. SPIE 3343, High-Power Laser Ablation, (14 September 1998); doi: 10.1117/12.321541
Show Author Affiliations
Andrea Cavalleri, Univ.-Gesamthochschule Essen and Univ. degli Studi di Pavia (United States)
Klaus Sokolowski-Tinten, Univ.-Gesamthochschule Essen (Germany)
Joerg Bialkowski, Univ.-Gesamthochschule Essen (Germany)
Dietrich von der Linde, Univ.-Gesamthochschule Essen (Germany)

Published in SPIE Proceedings Vol. 3343:
High-Power Laser Ablation
Claude R. Phipps, Editor(s)

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