1,721,051 research outputs found
Fundamental study and analytical applications of nanoparticle-enhanced laser-induced breakdown spectroscopy (NELIBS) of metals, semiconductors and insulators
No full textNanoparticle-Enhanced Laser-Induced Breakdown Spectroscopy (NELIBS) is a recently proposed method to efficiently increase the LIBS emission signal of metals up to 2 orders of magnitude, by depositing metal nanoparticles (NPs) on the sample surface (De Giacomo A, Gaudiuso R, Koral C, Dell’Aglio M, De Pascale O Anal Chem 85). This considerable emission enhancement has been ascribed to two effects: (1) an improvement in the ablation effect, and (2) a more efficient production of seed electrons by field emission, in turn due to the enhancement of the laser electromagnetic field induced by the NPs themselves (De Giacomo A, Gaudiuso R, Koral C, Dell’Aglio M, De Pascale O Acta Part B, 98)
Laser Induced Plasma Spectroscopy by Air Spark Ablation
No full textIn this work, a diagnostic method for solid layer analysis based on LIBS (laser induced breakdown spectroscopy) has been proposed for minimizing the damage on the sample surface. In this method the focus of laser is placed some millimetres distance from the target surface so that an air spark is generated close to the target surface. The particles are removed from the target mainly by air plasma etching instead of direct laser-solid interaction. In this way, it is not necessary to expose the target surface to high laser energy so that the damage on the sample is really superficial. Here preliminary results on a hard alloy as 25CrMo4 and on a sintered TiO tablet are shown
The effect of Oxygen Discharge on Pulsed Laser Deposition of Metallic Oxides
No full textIn this work final results on TiO2 film deposition by Plasma Assisted Pulsed Laser Deposition (PAPLD) with an rf biased substrate are presented. In previous work it has been shown that PAPLD is an improvement over conventional PLD for the elimination of particulates in high refractive index thin film deposition. This paper will give a comparison between conventional PLD and PAPLD on the stoichiometry, morphology, and optical properties of deposited TiO2 films. It will be demonstrated that oxygen rf discharge during the PLD process makes incorporation of oxygen into the depositing films extremely effective. This effect of the rf discharge allows operation of the PLD process at a lower oxygen background pressure while enhancing the deposition rate. Also, the production of a good quality TiO2 film by PAPLD using a pure metal titanium target will be shown
A laser beam photolitographic system for integrated optics applications : Ti-diffused LiNbO3 directional couplers
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Spectroscopic investigation of laser-water interaction beyond the breakdown threshold energy
No full textThe interaction between ns-laser pulse at 532 nm and water, or heavy water (deuterium dioxide), has been studied by Stimulated Raman Scattering (SRS) and optical emission spectroscopy. Both the photolysis and breakdown processes have been considered. When the photolysis is the main process, structural change in water occurs as a consequence of electron and proton hydration. The rearrangement of the water structure and the subsequent photon absorption by free electrons raising the breakdown threshold occur. Moreover, charge separation in bulk water, under laser induced electromagnetic field, leads to a notable enhancement of the SRS signal. On the other hand, for a high laser pulse energy density, electrons gain energy enough to escape from the hydrating water structure, generating electron impact dominated plasma
Mechanisms and processes of pulsed laser ablation in liquids during nanoparticle production
Full text linkIn the last decade Pulsed Laser Ablation in Liquids (PLAL) has been widely investigated from the fundamental point of view, and various theories have been proposed. Although many important achievements have been obtained by the scientific community, many aspects still need to be clarified and many contradictions arise when comparing the interpretation of similar experiments carried out by different authors. In this paper we have reconsidered previous works focused on specific processes and stages of the PLAL, in order to outline a modern and comprehensive point of view of the overall physical aspects of PLAL. With this aim, several simultaneous diagnostic methods have been applied during the production of metallic nanoparticles (NPs), i.e. optical emission spectroscopy and fast imaging for the investigation of the laser-induced plasma, shadowgraph for the study of the cavitation bubble, and Double Pulse Laser Ablation in Liquid (DP-LAL) and laser scattering for the investigation of NPs location and mechanisms of release in solution. The connection between the various stages of the DP-LAL allows understanding the main characteristics of the produced NPs and the typical timescales of the basic mechanisms involved in PLAL
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