Isolated nanoparticles of the wide band gap II−VI semiconductors CdS and ZnS were produced by ultrafast pulsed laser deposition using pulses of ≈300 fs at two wavelengths of 527 and 263 nm. Upon repetitive target irradiation, the isolated nanoparticles assemble to form a nanostructured film whose structural and chemical properties are compared to those of the targets. UV ablation at 263 nm yields nanoparticles of 5 nm average diameter in the case of CdS. At this wavelength the crystalline phase and stoichiometry of the films markedly differ from those of the target. At 527 nm the average size of the nanoparticles is larger, about 13 nm, but the deposits keep the structural and chemical characteristics of the target. For ZnS the size of the nanoparticles is larger than for CdS although their properties also resemble those of the target when they are produced upon irradiation in the visible. The results obtained allow discussion of the interplay between the light absorption step, the plume dynamics, and the film growth and their impact on the structure and nanometer morphology of the deposited material, while at the same time they exemplify the possibility of their control through the choice of the wavelength of the femtosecond pulses
Third and fifth harmonic generation of an IR (1.064 μm) pulsed laser has been produced in ablation plasmas of the wide bandgap semiconductors CdS and ZnS. The study of the temporal behaviour of the harmonic emission has revealed the presence of distinct compositional populations in these complex plasmas. Species ranging from atoms to nanometre-sized particles have been identified as emitters, and their nonlinear optical properties can be studied separately due to strongly differing temporal behaviour. At short distances from the target (<1 mm), atomic species are mostly responsible for harmonic generation at early times (<500 ns), while clusters and nanoaggregates mostly contribute at longer times (>1 μs). Harmonic generation thus emerges as a powerful and universal technique for ablation plasma diagnosis and as a tool to determine the nonlinear optical susceptibility of ejected clusters or nanoparticles.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.