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This study investigated the effects of the post-O2-annealing process on light emission from silicon nanocrystals. Using pulsed laser ablation in an O2-filled atmosphere, the SiOx (x<2) thin layers were synthesized prior to O2-annealing. We observed a strong photoluminescence from the silicon nanocrystals embedded in the annealed layers at 500 °C, which depended on the post-O2-annealing time. We also found that the interface property between the silicon nanocrystal and stoichiometric SiO2 matrix is critical for efficient light emission. The electroluminescence spectra in the visible range were obtained above the on-current density of 0.7 A/cm2 under several forward-bias voltages. The blueshift in the electroluminescence was attributed to the band-filling effect under high current injection mode. The external emission efficiency was estimated to be about 0.3% by using the band-filling model. [ABSTRACT FROM AUTHOR]

Time-resolved optical emission spectroscopy was employed to examine the temporal properties of a plume formed by laser ablation of a graphite target in He, N2, and Ar background gases. Time-dependent spectroscopic temperatures of electronically excited C2 and CN molecules generated in the plume at different background gases and pressures were derived by simulation of the emission spectra. The rotational temperature of CN molecules was significantly higher than the vibrational temperature. This indicates that they are formed in the gas phase by the chemical reaction C2+N2→CN. At pressure above 0.5 Torr, the temperature in each background gas was apparently in the order of Ar>N2>He while there was no such gas dependence at 0.1 Torr. The expansion dynamics and cooling rate of the plume turned out to be highly dependent on the background gas and its pressure. [ABSTRACT FROM AUTHOR]

Mass spectral distributions and time-of-flight spectra of C[sup +][sub n] (n = 1-24) ions escaping from a carbon plasma plume generated by laser (λ = 1064 nm) ablation of a graphite target are analyzed to shed light on their formation mechanisms, expansion dynamics, and laser-plume interaction. In particular, by shining the whole or a slice of the plume with a photodissociation laser (λ=266 nm) delayed with respect to the ablation laser, we examine the effects of the laser-plume interaction on the mass distribution as well as photodissociation channels of carbon-cluster cations. Also, we present experimental data that show a clear linear dependence of the velocities of C[sup +][sub n] ions on 1/&Mradic;. This result confirms that C[sup +][sub n] ions are mainly accelerated by a transient local electric field in the plume. [ABSTRACT FROM AUTHOR]

Presents information on a mass spectroscopic studies on a reactive laser ablation of YBa...Cu...O... in a pulsed oxygen jet. Ion mass spectra with oxygen jet on and off; Dependence of wavelength; Conclusion.

Er-doped SiOx thin films were fabricated by laser ablation of a Si:Er2O3 target in He atmosphere. We have measured the photoluminescence (PL) at 1.54 μm for the films grown at different He pressures and found that the oxygen density of the grown film that strongly influences the PL intensity is highly correlated with the ambient He pressure. This manifests that oxygen density of the film can be controlled in an inert atmosphere to maximize PL intensity when we adopt pulsed laser deposition (PLD) technique to deposit Er-doped SiOx thin films. Also, we have examined the temperature dependence of PL and observed that the thermal quenching is greatly reduced for the PLD-grown films. [Copyright &y& Elsevier]

Highlights: [•] We prepared polyynes by laser ablation of a graphite target in water at different wavelengths and energies. [•] The amount of polyynes so produced turned out to increase at longer wavelength. [•] In order to investigate the effects of various physical parameters on the polyynes chain length, we compared the branching ratios. [Copyright &y& Elsevier]

Silver nanoparticles were synthesized by laser (Nd:YAG, λ=1064 nm) ablation of a silver target immersed in various concentrations of NaCl solutions as well as in neat water. The concentration dependence of the surface plasmon absorption at around 400 nm was examined by analyzing the absorbance and peak shape. Significant changes in the peak intensity and full width at half maximum (FWHM) were observed. Typically, the size of the silver nanoparticles produced in 5 mM NaCl solution ranged from 5 to 50 nm, with an average size of 26 nm. Also, fragmentation of silver nanoparticles by absorption of 355 nm laser light was found to be highly effective. [Copyright &y& Elsevier]

Abstract: Polyynes were prepared by liquid-phase laser ablation of a graphite target at 1064nm and identified by analyzing UV absorption spectra in deionized water and various aqueous solutions. We observed that major UV absorption peaks coincide with the electronic transitions corresponding to linear hydrogen-capped polyynes (C n H2: n =6, 8, 10). The peak intensities increased when polyynes were produced by irradiating the target immersed in acidic media, while those were relatively weak in basic media. This leads us to conclude that OH− or H+ ions play a certain role in the formation of polyynes. [Copyright &y& Elsevier]

Highlights: [•] Post-irradiation can change the size distributions of gold nanoparticles. [•] There is a strong wavelength-dependence in post-irradiation. [•] Gold nanoparticles are most stable when they are post-irradiated at 355nm. [Copyright &y& Elsevier]

Abstract: Zinc oxide (ZnO) nanoparticles were prepared in neat deionized water by laser ablation with various ablation times (10–40min), fluences (50–130mJ/pulse), and wavelengths (1064, 532, and 355nm). The size and shape of the nanoparticles were affected only slightly by the ablation time and fluence at a wavelength of 1064nm, which was explained by a dynamic formation mechanism with surface charge effects. The nanoparticles formed by ablation at 355nm had a distinctive wire-shape with a small diameter, which was attributed to a continuous fragmentation and formation mechanism. [Copyright &y& Elsevier]

Abstract: By adopting a fast photography and time-resolved optical emission spectrometry, we have investigated the effects of transverse magnetic field on the expansion dynamics and enrichment of Zn atoms and Zn+ ions in a plume produced by laser ablation of a Zn target in oxygen atmosphere. Plume splitting due to the magnetic field was apparent but the splitting patterns of Zn and Zn+ were totally different. The surface morphology and photoluminescence characteristics also changed significantly. In particular, the growth rate increased by as much as 2.4–4.3 times compared to the conventional PLD method. [Copyright &y& Elsevier]

Abstract: Mg-doped ZnO thin films were fabricated by laser ablation of Zn:Mg targets consisting of Mg metallic strips and Zn disk in oxygen atmosphere with a goal to facilitate convenient control of Mg contents in the films. The characteristics of the deposited films were examined by analyzing their photoluminescence (PL), X-ray diffraction and X-ray photoelectron spectroscopy (XPS) spectra. Mg contents as analyzed by XPS indicate that the target composition is fairly transferred to the deposited films. The wurtzite structure of ZnO was conserved even for the highly doped ZnO films and there was no Mg- or MgO-related XRD peaks. With increase in the Mg content, the bandgap and PL peak energy shifted to blue and the Stokes shift became larger. [Copyright &y& Elsevier]