The mechanism of nanobump formation in femtosecond pulse laser nanostructuring of thin metal films

• Published in: Applied physics. A, Materials science & processing Vol. 92; no. 4; pp. 791 - 796
• Main Authors: Ivanov, Dmitriy S., Rethfeld, Baerbel, O’Connor, Gerard M., Glynn, Thomas J., Volkov, Alexey N., Zhigilei, Leonid V.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.09.2008; Springer Nature B.V
• Subjects: Applied physics; Characterization and Evaluation of Materials; Compressive properties; Computer simulation; Condensed Matter Physics; Conduction heating; Conductive heat transfer; Continuum modeling; Femtosecond; Femtosecond pulsed lasers; Laser beam heating; Lasers; Machines; Manufacturing; Materials science; Metal films; Molecular dynamics; Nanocomposites; Nanomaterials; Nanostructure; Nanotechnology; Optical and Electronic Materials; Physics; Physics and Astronomy; Processes; Simulation; Substrates; Surfaces and Interfaces; Thin Films; 64.70.D; 02.70.Ns; 61.80.Az
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-008-4712-y

The physical mechanisms responsible for the formation of nanobump structures on a surface of a thin metal film irradiated by a tightly focused femtosecond laser pulse are investigated in a large-scale molecular dynamics simulation. The simulation is performed with a combined atomistic-continuum model adapted for an adequate representation of laser-induced processes at the length-scale of the entire laser spot. The relaxation of the compressive stresses generated by the fast laser heating is identified as the main driving force responsible for the separation of the metal film from the substrate and formation of the nanobump. The kinetics of the transient melting and resolidification, occurring under conditions of the fast cooling due to the two-dimensional electron heat conduction, defines the shape of the nanobump. The predictions of the simulation are related to the surface structures observed in femtosecond laser nanostructuring.