Synthesis and optical properties of lithium nanoparticles in wide-gap dielectrics

Characteristics of LiF crystals irradiated by pulsed laser radiation with pulse duration of 50 fs, an energy of about 5 mJ, and a wavelength of 950 nm were studied. After single-pulse irradiation, a band with maximum at wavelength of 450 nm related to formation of F3 color centers was observed in the extinction spectra of sample. With an increase in the number of pulses, components associated with more complex aggregate F3 (R), F3, and F4 (N) centers appear in the band structure. The observed association of F3+ centers leads to the formation of larger aggregates up to the precipitation of nanoscale lithium clusters, which is confirmed by comparison of spectra of the crystals irradiated with laser pulses and the crystals irradiated with high-energy Li+ ions with use of ion implanter. Atomic force microscopy study confirmed the conclusion that lithium nanoparticles with sizes in the range of 60–90 nm were formed in surface layer of LiF crystal as a result of laser irradiation.