Study of Si/SiO 2 nanoparticles produced by laser ablation

Despite of the fact that in the last years a significant effort have been devoted to pulsed laser ablation (PLA), the problem of micro and nanoparticles have not been unambiguous presented (to our knowledge). In this work, we studied the size, size distribution and structure of the particles produced by laser ablation and luminescence as well. Scanning and transmission electron microscopy, X-ray diffraction and optical spectroscopy have been used. The investigations were made on Si/SiO₂ nanopowders as produced, without any post-treatment (chemical, thermal, etc.). The experimental parameters were: silicon target, laser wavelength 355/532 nm, pulse duration 5 ns, repetition rate 10 Hz, fluence 4-8 J/cm², argon/helium, 250-550 mbar, flow rate 1 l/min. Our investigations have shown that the particles are distributed in two main classes: one, with the size 0.1-1 μm, and the other with the diameter less than 14 nm. Our evaluation for optimal experimental conditions shown that around 78% (vol.) of particles are < 10 nm and almost 50% have diameters in the range 2-5 nm. The photo and cathodoluminescence were in the range 400-1000 nm, with main peak at 690-725 nm.