14 September 1998 Time-of-flight mass spectroscopy of femtosecond laser ablation of solid surfaces
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Proceedings Volume 3343, High-Power Laser Ablation; (1998) https://doi.org/10.1117/12.321541
Event: High-Power Laser Ablation, 1998, Santa Fe, NM, United States
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.
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Andrea Cavalleri, Andrea Cavalleri, Klaus Sokolowski-Tinten, Klaus Sokolowski-Tinten, Joerg Bialkowski, Joerg Bialkowski, Dietrich von der Linde, Dietrich von der Linde, } "Time-of-flight mass spectroscopy of femtosecond laser ablation of solid surfaces", Proc. SPIE 3343, High-Power Laser Ablation, (14 September 1998); doi: 10.1117/12.321541; https://doi.org/10.1117/12.321541
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