Theoretical determination of the ablation rate of metals in multiple-nanosecond laser pulses irradiation regime

• Published in: Applied surface science Vol. 253; no. 15; pp. 6353 - 6358
• Main Authors: Stafe, Mihai, Negutu, Constantin, Popescu, Ion M.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2007; Elsevier Science
• Subjects: Ablation rate; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; Impact phenomena (including electron spectra and sputtering); Laser ablation; Laser-beam impact phenomena; Photo-thermal model; Physics; Laser ablation; 40; Photo-thermal model; Ablation rate; Patterning; Physical radiation effects; Theoretical study; Pulsed laser deposition; Computerized simulation; Pulsed lasers; Film growth; Laser radiation; Laser targets; Modelling; Laser ablation technique; Melts
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2007.01.060

A detailed understanding of the physical determinants of the ablation rate in multiple nanosecond laser pulses regime is of key importance for technological applications such as patterning and pulsed-laser deposition. Here, theoretical modeling is employed to investigate the ablation of thick metallic plates by intense, multiple nanosecond laser pulses. A new photo-thermal model is proposed, in which the complex phenomena associated to the ablation process are accounted for as supplementary terms of the classical heat equation. The pulsed laser ablation in the nanosecond regime is considered as a competition between thermal vapourization and melt ejection under the action of the plasma recoil pressure. Computer simulations using the photo-thermal model presented here and the comparison of the theoretical results with experiment indicate two different mechanisms that contribute to the decrease of the ablation efficiency. First, during the ablation process the vapour/plasma plume expanding above the irradiated target attenuates the laser beam that reaches the sample, leading to a marked decrease of the ablation efficiency. Additional attenuation of the laser beam incident on the sample is produced due to the heating of the plasma by the absorption of the laser beam into the plasma plume. The second mechanism by which the ablation efficiency decreases consists of the reduction of the incident laser intensity with the lateral area, and of the melt ejection velocity with the depth of the hole.