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K: Kurzzeitphysik
K 6: Laserstrahl-Wechselwirkungen
K 6.6: Vortrag
Mittwoch, 11. März 1998, 15:15–15:30, H8
Time of flight mass spectroscopy of femtosecond laser ablation of solid surfaces — •A. Cavalleri, K. Sokolowski-Tinten, J. Bialkowski, M. Schreiner, and D. von der Linde — Institut f"ur Laser- und Plasmaphysik, Universit"at-GHS-Essen, D-45117 Essen
We present time of flight (TOF) measurements of particle desorption after excitation of solid surfaces (Si, GaAs, Al) with a 100 fs, 620 nm laser pulse. In the case of Gallium particles from GaAs surfaces, we are able to observe the transition between free flow (below the ablation threshold Fth) to the adiabatic expansion regime and the corresponding transformation of the TOF distributions from half-range to drifted Maxwellian. Below Fth, we observe progressive overheating of the molten material up to about 3000 K. Above Fth, the measured temperature progressively decreases and levels off above about 1.5× Fth. We also observe the appearance of a non-zero center of mass velocity which progressively increases as a function of pump energy. In the case of Silicon we detect clusters of up to 7 atoms.