Optical field enhancement effects in laser-assisted particle removal |
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Authors: | M Mosbacher H-J Münzer J Zimmermann J Solis J Boneberg P Leiderer |
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Institution: | (1) University of Konstanz, Department of Physics, Fach M676, 78457 Konstanz, Germany, DE;(2) Instituto de Optica, CSIC, Serrano 121, 28006 Madrid, Spain, ES |
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Abstract: | We report on the role of local optical field enhancement in the neighborhood of particles during dry laser cleaning (DLC)
of silicon wafer surfaces. Samples covered with spherical colloidal particles (PS, SiO2) and arbitrarily shaped Al2O3 particles with diameters from 320–1700 nm were cleaned using laser pulses with durations from 150 fs to 6.5 ns and wavelengths
ranging from 400–800 nm. Cleaned areas were investigated with scanning electron and atomic force microscopy. Holes in the
substrate with diameters of 200–400 nm and depths of 10–80 nm, depending on the irradiation conditions, were found at the
former positions of the particles. For all pulse durations analyzed (fs, ps, ns), holes are created at laser fluences as small
as the threshold fluence. Calculations of the optical field intensities in the particles’ neighbourhood by applying Mie theory
suggest that enhancement of the incident laser intensity in the near field of the particles is responsible for these effects.
DLC for sub-ns pulses seems to be governed by the local ablation of the substrate rather than by surface acceleration.
Received: 31 May 2000 / Accepted: 7 September 2000 / Published online: 22 November 2000 |
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Keywords: | PACS: 81 65 C 79 60 Bm |
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