Femtosecond laser ablation of diamond-like carbon films Gabriel Dumitru a,* , Valerio Romano a , Heinz P. Weber a , Sergei Pimenov b , Taras Kononenko b , Marc Sentis c , Jo ¨rg Hermann c , Se ´bastien Bruneau c a Institute of Applied Physics, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland b General Physics Institute, Russian Academy of Sciences, 38 Vavilov Street, 117942 Moscow, Russia c LP3 FRE2165 CNRS, Faculte ´ des Sciences de Luminy, Universite ´ de la Me ´diterrane ´e, Case 917, 13288 Marseille, France Received 21 February 2003; received in revised form 17 August 2003; accepted 17 August 2003 Abstract Diamond-like carbon (DLC) coatings were deposited on Si substrates using a hot filament diode discharge and they were irradiated with ultrashort laser pulses (800 nm, 150 fs, <4 J/cm 2 ). The laser-treated films were examined using optical microscopy, Raman spectroscopy, SEM, AFM and white-light interferometery. Damage threshold of 0.16 J/cm 2 and ablation rates below 110 nm/pulse were determined. Changes in the structure of the laser-irradiated films were showed by means of Raman investigations. The laser-treated samples were etched and the depths of modified material layers were determined. Ablation experiments with longer laser pulses (1064 nm, 100 ns, <3 J/cm 2 ) were also performed and the irradiated DLC films were afterwards analyzed using the same procedures. Dissimilarities in the structure changes induced by fs-and ns-laser irradiation were observed and comments are given. # 2003 Elsevier B.V. All rights reserved. Keywords: Femtosecond pulses; Diamond-like carbon; Ablation properties; Structure changes 1. Introduction Diamond-like carbon (DLC) (form of amorphous carbon with a significant fraction of sp 3 bonds [1]) is of extended interest in various scientific and industrial fields. By controlling the deposition parameters, dia- mond-like carbon films can be made very smooth, may exhibit a large hardness and can be almost chemically inert. Properties and applications of DLC films have been systematically treated in recent literature [1–6] and we mention briefly that: (i) they have great potential as low wear and low friction coatings; (ii) these films are promising materials in photolitho- graphic techniques; (iii) they are used for microelec- tronic devices; (iv) they can act as antireflective coatings for IR components. In certain applications there is an interest in pattern- ing DLC films, in order to induce directional friction properties or to create narrow conductive lines. Plasma, chemical, or laser [7,8] techniques can be used to achieve such modifications. Using laser-patterned DLC coated surfaces we showed [9] that the advantages of DLC tribological coatings can be combined with the beneficial effects [10,11] of laser surface patterning. In this work we investigate the changes induced in hydrogenated amorphous carbon films by their irradia- tion with femtosecond laser pulses. This type of laser treatment may be used to induce structure changes in a Applied Surface Science 222 (2004) 226–233 * Corresponding author. Tel.: þ41-31-6318940; fax: þ41-31-6313765. E-mail address: dumitru@iap.unibe.ch (G. Dumitru). 0169-4332/$ – see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2003.08.031