Case study on the ultrafast laser ablation of thin aluminum films: dependence on laser parameters and film thickness

• Published in: Applied physics. A, Materials science & processing Materials science & processing, 2016-03, Vol.122 (3), p.1-8, Article 215
• Main Authors: Olbrich, M., Punzel, E., Roesch, R., Oettking, R., Muhsin, B., Hoppe, H., Horn, A.
• Format: Article
• Language: English
• Subjects: Ablation; Aluminum; Characterization and Evaluation of Materials; Computer simulation; Condensed Matter Physics; Emerging trends in photo-excitations and promising new laser ablation technologies; Film thickness; Invited Paper; Machines; Manufacturing; Mathematical models; Nanotechnology; Optical and Electronic Materials; Physics; Physics and Astronomy; Processes; Surfaces and Interfaces; Thickness; Thin Films; Thresholds
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-016-9736-0

Laser ablation using ultra-short pulsed laser radiation allows the removing of thin films with very high spatial resolution, and working with high repetition rate as well with high through-put. The ultrafast ablation of thin films of aluminum on float glass is investigated using focused femtosecond laser radiation ( λ  = 1028 nm, t H  = 200 fs, sech 2 , p f  = 1 MHz) as function of the number of pulses N p per point (1–10) and the film thickness d (30–300 nm). It is observed that two thresholds are derived simultaneously for thin films with a thickness thicker than 100 nm by irradiating the metal with single pulsed laser radiation exhibiting a Gaussian intensity distribution: one threshold for gentle ablation H thr,gentle and the other for strong ablation H thr,strong . Multi-pulse irradiation varying the number of pulses per point identifies the incubation effect described by Jee et al. (J Opt Soc Am B 5(3):648, 1968 ). This model was applied on the thresholds for gentle and strong ablation. Also, varying the layer thickness reducing the thresholds for thin films due heat accumulation. To quantify the experimental data, numerical simulations solving the coupled heat transfer equation of the two-temperature model were performed. A new approach including the temperature dependence of the reflectivity is presented based on the model proposed by Brückner et al. (J Appl Phys 66:1326, 1989 ). The results of the simulation fit qualitative well to the experimental data of gentle ablation. Theoretical investigation for double pulses with a variable pulse separation time of 1–300 ps were performed in comparison with a single pulse.