Evolution of size distribution, optical properties, and structure of Si nanoparticles obtained by laser-assisted fragmentation

We investigate the physical properties of Si-based nanoparticles produced by an environment-friendly three-step method relying on: (1) laser ablation of a solid target immersed in water, (2) centrifugation and separation, and (3) laser-assisted fragmentation. The evolution of size distribution is fo...

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Bibliographic Details
Published in:Applied physics. A, Materials science & processing Materials science & processing, 2017-05, Vol.123 (5), p.1-9, Article 359
Main Authors: Plautz, G. L., Graff, I. L., Schreiner, W. H., Bezerra, A. G.
Format: Article
Language:English
Subjects:
Applied physics
Characterization and Evaluation of Materials
Condensed Matter Physics
Laser ablation
Machines
Manufacturing
Materials science
Nanoparticles
Nanotechnology
Optical and Electronic Materials
Optical properties
Photoluminescence
Photon correlation spectroscopy
Physical properties
Physics
Physics and Astronomy
Processes
Size distribution
Surfaces and Interfaces
Thin Films
Transmission electron microscopy
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Summary:We investigate the physical properties of Si-based nanoparticles produced by an environment-friendly three-step method relying on: (1) laser ablation of a solid target immersed in water, (2) centrifugation and separation, and (3) laser-assisted fragmentation. The evolution of size distribution is followed after each step by means of dynamic light scattering (DLS) measurements and crosschecked by transmission electron microscopy (TEM). The as-ablated colloidal suspension of Si nanoparticles presents a large size distribution, ranging from a few to hundreds of nanometers. Centrifugation drives the very large particles to the bottom eliminating them from the remaining suspension. Subsequent irradiation of height-separated suspensions with a second high-fluence (40 mJ/pulse) Nd:YAG laser operating at the fourth harmonic ( λ = 266 nm) leads to size reduction and ultra-small nanoparticles are obtainable depending on the starting size. Si nanoparticles as small as 1.5 nm with low dispersion ( ± 0.7 nm) are observed for the uppermost part after irradiation. These nanoparticles present a strong blue photoluminescence that remains stable for at least 8 weeks. Optical absorption (UV–Vis) measurements demonstrate an optical gap widening as a consequence of size decrease. Raman spectra present features related to pure silicon and silicon oxides for the irradiated sample. Interestingly, a defect band associated with silicon oxide is also identified, indicating the possible formation of defect states, which, in turn, supports the idea that the blue photoluminescence has its origin in defects.
ISSN:0947-8396
1432-0630
DOI:10.1007/s00339-017-0961-y