Bochum 2002 – wissenschaftliches Programm

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K: Kurzzeitphysik

K 3: Laser-Anwendungen /-Materialbearbeitung

K 3.5: Vortrag

Donnerstag, 21. März 2002, 11:50–12:05, HZO 80

Tracking of Laser-Cleaning of Metal Surfaces by Time-Resolved Mirror Electron Microscopy — •Harry Kleinschmidt and Oleg Bostanjoglo — Optisches Institut, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany

Cleaning of surfaces of metal films by laser pulses was investigated in real time by a mirror electron microscope [1]. Films of Bi, Cr, and Ni, evaporated on quartz glass substrates, were treated by 25 ns single and double laser pulses (pulse spacing 1 µs << time for the deposition of a monolayer from the ambient vacuum). A double pulse is used to expose a surface devoid of adsorbates and oxides to the cleaning second pulse. Native adsorbates, oxides and part of the pulse-molten metal evaporate during the first 10 ns after the heating laser pulse. A regrowth of a surface layer starts as early as about 100 ns afterwards. It is caused by diffusion of dissolved oxygen from within the bulk melt to its cleaned surface and by segregation at the solid/liquid interface. Cracking of the laser pulsed Cr film, causing the known partial exfoliations in the final structures, begins at about 300 ns after the laser pulse. This work was in part supported by the Deutsche Forschungsgemeinschaft. [1] H. Kleinschmidt, O. Bostanjoglo, Rev. Sci. Instrum. 72, 3898 (2001).