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Published July 2011 | public
Journal Article

Irradiation of amorphous Ta_(42)Si_(13)N_(45) film with a femtosecond laser pulse

Abstract

Films of 260 nm thickness, with atomic composition Ta_(42)Si_(13)N_(45), on 4" silicon wafers, have been irradiated in air with single laser pulses of 200 femtoseconds duration and 800 nm wave length. As sputter-deposited, the films are structurally amorphous. A laterally truncated Gaussian beam with a near-uniform fluence of ~0.6 J/cm^2 incident normally on such a film ablates 23 nm of the film. Cross-sectional transmission electron micrographs show that the surface of the remaining film is smooth and flat on a longrange scale, but contains densely distributed sharp nanoprotrusions that sometimes surpass the height of the original surface. Dark field micrographs of the remaining material show no nanograins. Neither does glancing angle X-ray diffraction with a beam illuminating many diffraction spots. By all evidence, the remaining film remains amorphous after the pulsed femtosecond irradiation. The same single pulse, but with an enhanced and slightly peaked fluence profile, creates a spot with flat peripheral terraces whose lateral extents shrink with depth, as scanning electron and atomic force micrographs revealed. Comparison of the various figures suggests that the sharp nanoprotrusions result from an ejection of material by brittle fraction and spallation, not from ablation by direct beam–solid interaction. Conditions under which spallation should dominate over ablation are discussed.

Additional Information

© 2011 Springer-Verlag. Received: 10 September 2010; Accepted: 6 October 2010; Published online: 14 December 2010. We thank Dietmar Bertsch, NTB at Buchs (SG), who deposited the films and A. Dommann, CSEM at Neuchatel (NE), who executed the X-ray diffraction experiment. Special thanks go to André Koch for his input on shock waves. The resistivity of the Ta42Si13N45 film from 3 to 500 K was measured at the I. Physikalisches Institut, University of Göttingen (Konrad Samwer) whom we gratefully acknowledge. We are also indebted to Willy Lüthy, IAP at University of Bern for taking scanning electron micrographs.

Additional details

Created:
August 19, 2023
Modified:
October 23, 2023