ИСТИНА

Femtosecond laser ablation of porous medium is of great interest due to increase in these media as linear-optical effects, such as the enhancement of the Raman scattering efficiency [1]; as non-linear-optical effects, for example the enhancement of the cubic nonlinear susceptibility [2]. The nanoparticles, formed at these conditions can be used for potential applications in biomedical field as contrasting agents in optical coherence tomography [3] due to biocompatibility and biodegradability of silicon nanoparticles. This paper presents the results of experiments of the nanoparticle formation as a result of femtosecond laser ablation of porous silicon p-type and Silicon nanowires in helium and hexane (С6H14). During the experiment, the target was irradiated with Cr:forsterite femtosecond laser (1250 nm, 180 fs) pulses at room temperature. Atomic-force microscopy analyze of samples, formed by ablation of por-Si wafers in helium evidenced about monotonic dependence of nanoparticle size variation on the buffer gas pressure: the nanoparticle size decreased with increasing pressure. Raman scattering measurements indicated the presence of crystalline phase of silicon, which corresponds to a 520 cm-1 line. The carried out experiments indicated possibility to fabricate silicon nanoparticles by means of laser ablation of porous silicon films with higher mass yield in comparison with nanoparticles, formed by laser ablation of crystalline silicon. This fact could be related with lower ablation threshold at the case of porous silicon. In addition, the observed photoluminescence of porous silicon samples in the visible range provides possibilities for potential applications of the formed samples in biomedicine. This work was financially supported by the Russian Foundation for Basic Research (project 15-32-20227). [1]. L.A. Osminkina, K.A. Gonchar, V.S. Marshov et al. Nanoscale Research Letters 7, 524-529 (2012) [2]. V.Ya. Gayvoronsky, L.A. Golovan, M.A. Kopylovsky et al. Quantum Electronics 41, 257-261 (2011) [3]. M.Yu. Kirillin, E.A. Sergeeva, P.D. Agrba et al. Laser Phys. 25 075604(1) -075604(7) (2015)