1,721,114 research outputs found
Ultra-short Pulsed Laser Deposition of Gallium Arsenide: a Comprehensive Study
No full textA Gallium Arsenide target has been ablated by using a frequency-doubled Nd:glass laser with a pulse duration of 250 fs and thin films have been deposited in vacuum. The plasma produced by the ablation process and the deposited films have been studied by several different techniques, including optical emission spectroscopy, ICCD fast imaging and electron microscopies, X-ray diffraction, Raman spectroscopy, respectively. The data evidence that the films, which composition shows an excess of Ga, are formed by the coalescence of a large number of nanoparticles. These results, even if the plasma does not evidence the presence of nanoparticles, seem to indicate that the ablation-deposition mechanism is the same found for the majority of the other systems deposited by ultra-short pulse lasers
Diamond-like carbon thin films produced by femtosecond pulsed laser deposition of fullerite
No full textDiamond-like carbon films have been deposited from a fullerite target by ultra-short pulsed laser deposition technique. The results indicate that the films morphology and structure, determined by scanning electron microscopy, atomic force microscopy and energy dispersive X-ray diffraction, depend strongly on the substrate temperature. X-ray photoelectron. X-ray Auger electron, Raman and surface enhanced Raman scattering spectra indicate that the fs-DLC films composition involves a mixed sp, sp(2) and sp(3) carbon network consisting of aromatic rings and sp(3) diamond-like structures linked by chains of different lengths and composition. The films deposited at room temperature, presenting the higher content of sp(3) carbon (48%), also contain C(60) crystalline phase and show a very high hardness of 49 GPa
Laser ablation of GaAs in liquid: the role of laser pulse duration
No full textThe synthesis of gallium arsenide (GaAs) nanoparticles has attracted wide scientific and technological interest due to the possibility of tuning the GaAs NP (nanoparticle) band gap across the visible spectrum and their consequent use in optoelectronic devices. In recent years, laser ablation in liquid (LAL) has been widely used for the preparation of colloidal solutions of semiconducting and metallic nanoparticles, thanks to its flexibility. With the aim of highlighting the key role played by laser pulse duration on the ablation mechanism and on the properties of the obtained materials, laser ablation of a gallium arsenide target in acetone was performed using laser sources operating in two different temporal regimes: Nd:glass laser (l = 527 nm, pulse duration of 250 fs and frequency repetition rate of 10 Hz) and Nd:YAG laser (l = 532 nm, pulse duration of 7 ns and frequency repetition rate of 10 Hz). The ablation process was studied following the dynamics of the laser induced shock waves (SWs) and cavitation bubbles (CBs) by fast shadowgraphy, showing that CB dimension and lifetime is related to the laser pulse length. A characterization of the obtained materials by TEM (transmission electron microscopy) and microRaman spectroscopy have shown that quite spherical gallium oxide/GaAs nanoparticles can be obtained by nanosecond laser ablation.
On the other hand, pure polycrystalline GaAs nanoparticles can be produced by using an ultrashort laser source
Spectroscopic evidences for adsorption-induced polymerization of Terthiophene at silver surfaces
No full textAdsorption-induced conformational transition in 2,2’ bipyridine on silver surfaces: a Surface Enhanced Raman Scattering study
No full textUltrashort Pulsed Laser Ablation of Magnesium Diboride: Plasma Characterization and Thin Films Deposition
Full text linkA MgB2 target has been ablated by Nd:glass laser with a pulse duration of 250 fs. The plasma produced by the laser-target interaction, showing two temporal separated emissions, has been characterized by time and space resolved optical emission spectroscopy and ICCD fast imaging. The films, deposited on silicon substrates and formed by the coalescence of particles with nanometric size, have been analyzed by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. The first steps of the films growth have been studied by Transmission Electron Microscopy. The films deposition has been studied by varying the substrate temperature from 25 to 500°C and the best results have been obtained at room temperature
The use of self assembled monolayers as nanometric spacers in surface enhanced Raman experiments
No full textInsight the lithiation process of Micro and Nanoparticles TiO2-Anatase based electrodes
No full textTiO2Size-dependent electrochemical propertiesFaradic and capacitive mechanismNegative electrode for lithium batterisoperando Raman spectroscop
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