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K: Kurzzeitphysik

K 4: Laser applications

K 4.1: Talk

Thursday, March 20, 2003, 15:15–15:30, F04

Ablation of Metal Films by High-Fluence Laser Pulses — •Holger Dömer and Oleg Bostanjoglo — Optisches Institut der TU Berlin, Straße des 17. Juni 135, 10623 Berlin

Ag, Al, Cr, Ge, and Ni films were processed by a Gaussian, 6 ns laser pulse at high fluences. The induced processes were investigated in a nanosecond transmission electron microscope by imaging and micro-diffraction. At lower fluences the ablation is started by defect-enhanced surface evaporation with melt displacement, and is completed by a delayed phase explosion. At higher fluences the heated center is vaporized by phase explosion with production of a plasma. A liquid network outside the center survives which is finally splashed by a hydrodynamic instability within 100-300 ns. The melts produced at low fluences (not vaporizing the film) reach their stationary short-range order after 10-40 ns, depending on the metal. Since the parameters needed for a simulation of the ablation (latent heats and surface tension) depend on the short-range order of the produced liquid, the tabulated values, which are valid for liquids in equilibrium, may therefore be not relevant.