Femtosecond laser processing of NiPd single and 5x(Ni/Pd) multilayer thin films

• Published in: Applied surface science 2017-09, Vol.417, p.16-22
• Main Authors: Petrović, S., Gaković, B., Zamfirescu, M., Radu, C., Peruško, D., Radak, B., Ristoscu, C., Zdravković, S., Luculescu, C.L., Mihailescu, I.N.
• Format: Article
• Language: English
• Subjects: Laser processing; Periodic structures
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2016.12.142

•The single NiPd and multilaye 5x(Pi/Pd) system were modified by femtosecond laser pulses.•Surface morphology was examined after single and multi-pulse irradiation in a function of pulse energies.•Laser-Induced Periodic Surface Structures were occurred as the low and high spatial frequency LIPSS.•Single pulse irradiation induced nanostructured modification solely on the surface of thin films.•Multipulse action induced damage/ablation of thin film and substrate with formation deep craters. Modification of single and complex nickel-palladium samples by laser processing in the femtosecond time domain was studied. The samples were processed by focused Ti:Sapphire laser beam (Clark CPA-2101) with 775nm laser wavelength, 2kHz repetition rate, 200fs pulse duration. The laser-induced morphological modifications have shown dependence on the applied fluences and number of laser pulses. The formed surface nanostructures on the single NiPd/Si and multilayer 5x(Ni/Pd)/Si systems are compared with individual Ni and Pd thin films. The results show an increase in surface roughness, formation of parallel periodic surface structures, appearance of hydrodynamic features and ablation of surface material. At low number of pulses (less than 10 pulses) and low pulse energies range (not over 1.7μJ), the two types of laser-induced periodic surface structure (LIPSS) can be observed: low and high spatial frequency LIPSS (HSFL and LSFL). For all samples, the measured LSFL periods were 720nm for the ripples created solely on thin film surfaces during the single pulse action. In the case of the multi-pulse irradiation, the periodicities of created LSFLs on the all investigated thin films have shown tendency to reduction with increasing of pulse energies.