The Experts below are selected from a list of 5454 Experts worldwide ranked by ideXlab platform
C Fotakis - One of the best experts on this subject based on the ideXlab platform.
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ultraviolet Laser microstructuring of silicon and the effect of Laser Pulse Duration on the surface morphology
Applied Surface Science, 2006Co-Authors: E Skantzakis, Vassilia Zorba, D G Papazoglou, I Zergioti, C FotakisAbstract:Abstract The study of the Laser Pulse Duration effect on the silicon micro-spikes morphology is presented. The microcones were produced by ultraviolet (248 nm) Laser irradiation of doped Si wafers in SF 6 environment. The Laser Pulse Duration was adjusted at 450 fs, 5 ps and 15 ns. We have analyzed the statistical nature of the spikes’ morphological characteristics, such as periodicity and apex angle by exploiting image processing techniques, on SEM images of the irradiated samples. The correlation of the quantitative morphological characteristics with the Laser parameters (Pulse Duration, Laser fluence and number of Pulses) provides new insight on the physical mechanisms, which are involved on the formation of Si microcones.
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role of Laser Pulse Duration and gas pressure in deposition of aln thin films
Journal of Applied Physics, 2001Co-Authors: E Gyorgy, C Fotakis, C Ristoscu, I N Mihailescu, Argyro Klini, N A Vainos, C Ghica, G Schmerber, Jacques FaerberAbstract:We investigated the relative merits and limits of Pulsed Laser deposition from AlN targets in vacuum and low-pressure nitrogen in obtaining stoichiometric and crystalline aluminum nitride thin films. We used two UV excimer Laser sources (λ=248 nm): a nanosecond system (τFWHM=30 ns) and, a subpicosecond (τFWHM=450 fs) system. The obtained structures were characterized by x-ray diffraction, electron microscopy in cross section, selected area electron diffraction, and profilometry. We demonstrated that the best results are obtained with the sub-ps Laser source in vacuum and in low pressure nitrogen when the AlN thin films are very pure, crystalline, clearly exhibiting a tendency to epitaxy. Metallic Al is present in the films deposited with the ns Laser source. We believe this is an effect of the gradual decomposition of AlN inside the crater on the target surface under multiPulse Laser irradiation.
Ahmed Hassanein - One of the best experts on this subject based on the ideXlab platform.
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influence of Laser Pulse Duration on extreme ultraviolet and ion emission features from tin plasmas
Physics of Plasmas, 2014Co-Authors: Sivanandan S. Harilal, M Polek, S M Hassan, Akira Endo, Ahmed HassaneinAbstract:We investigated the role of Laser Pulse Duration and intensity on extreme ultraviolet (EUV) generation and ion emission from a Laser produced Sn plasma. For producing plasmas, planar slabs of pure Sn were irradiated with 1064 nm Nd:YAG Laser Pulses with varying Pulse Duration (5–20 ns) and intensity. Experimental results performed at CMUXE indicate that the conversion efficiency (CE) of the EUV radiation strongly depend on Laser Pulse width and intensity, with a maximum CE of ∼2.0% measured for the shortest Laser Pulse width used (5 ns). Faraday Cup ion analysis of Sn plasma showed that the ion flux kinetic profiles are shifted to higher energy side with the reduction in Laser Pulse Duration and narrower ion kinetic profiles are obtained for the longest Pulse width used. However, our initial results showed that at a constant Laser energy, the ion flux is more or less constant regardless of the excitation Laser Pulse width. The enhanced EUV emission obtained at shortest Laser Pulse Duration studied is related to efficient Laser-plasma reheating supported by presence of higher energy ions at these Pulse Durations.
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the influence of Laser Pulse Duration and energy on icp ms signal intensity elemental fractionation and particle size distribution in nir fs la icp ms
Journal of Analytical Atomic Spectrometry, 2013Co-Authors: P K Diwakar, N L Lahaye, Ahmed Hassanein, Sivanandan S. Harilal, Pramod KulkarniAbstract:Laser parameters, typically wavelength, Pulse width, irradiance, repetition rate, and Pulse energy, are critical parameters which influence the Laser ablation process and thereby influence the LA-ICP-MS signal. In recent times, femtosecond Laser ablation has gained popularity owing to the reduction in fractionation related issues and improved analytical performance which can provide matrix-independent sampling. The advantage offered by fs-LA is due to shorter Pulse Duration of the Laser as compared to the phonon relaxation time and heat diffusion time. Hence the thermal effects are minimized in fs-LA. Recently, fs-LA-ICP-MS demonstrated improved analytical performance as compared to ns-LA-ICP-MS, but detailed mechanisms and processes are still not clearly understood. Improvement of fs-LA-ICP-MS over ns-LA-ICP-MS elucidates the importance of Laser Pulse Duration and related effects on the ablation process. In this study, we have investigated the influence of Laser Pulse width (40 fs to 0.3 ns) and energy on LA-ICP-MS signal intensity and repeatability using a brass sample. Experiments were performed in single spot ablation mode as well as rastering ablation mode to monitor the Cu/Zn ratio. The recorded ICP-MS signal was correlated with total particle counts generated during Laser ablation as well as particle size distribution. Our results show the importance of Pulse width effects in the fs regime that becomes more pronounced when moving from femtosecond to picosecond and nanosecond regimes.
Noriaki Miyanaga - One of the best experts on this subject based on the ideXlab platform.
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optimum Laser Pulse Duration for efficient extreme ultraviolet light generation from Laser produced tin plasmas
Applied Physics Letters, 2006Co-Authors: Tsuyoshi Ando, M. Murakami, S Fujioka, H Nishimura, Nobuyoshi Ueda, Yuzuri Yasuda, Keiji Nagai, T Norimatsu, K Nishihara, Noriaki MiyanagaAbstract:Conversion efficiencies (CEs) from incident Laser energy to 13.5nm light within a 2% bandwidth were measured with changing Laser Pulse Durations for Laser-produced tin plasmas. Experimental results indicate that the optimum Pulse Duration is determined by two parameters: one is the optical depth of tin plasma for 13.5nm light and the other is Laser absorption rate in 13.5nm emission-dominant region. The maximum CE of 2.2% is obtained with Pulse Duration of 2.3ns.
Le B Drogoff - One of the best experts on this subject based on the ideXlab platform.
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influence of the Laser Pulse Duration on Laser produced plasma properties
Plasma Sources Science and Technology, 2004Co-Authors: Le B Drogoff, J Margot, Francois Vidal, S Laville, M Chaker, Mohamad Sabsabi, T W Johnston, O BarthelemyAbstract:In the framework of Laser-induced plasma spectroscopy (LIPS) applications, time-resolved characteristics of Laser-produced aluminium plasmas in air at atmospheric pressure are investigated for Laser Pulse Durations ranging from 100 fs to 270 ps. Measurements show that for delays after the Laser Pulse longer than ~100 ns, the plasma temperature increases slightly with the Laser Pulse Duration, while the electron density is independent of it. In addition, as the Pulse Duration increases, the plasma radiation emission lasts longer and the spectral lines arise later from the continuum emission. The time dependence of the continuum emission appears to be similar whatever the Duration of the Laser Pulse is, while the temporal evolution of the line emission seems to be affected mainly by the plasma temperature. Finally, as far as spectrochemical applications (such as LIPS) of Laser-produced plasmas are concerned, this study highlights the importance of the choice of appropriate temporal gating parameters for each Laser Pulse Duration.
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influence of the Laser Pulse Duration on spectrochemical analysis of solids by Laser induced plasma spectroscopy
Applied Spectroscopy, 2004Co-Authors: Le B Drogoff, J Margot, S Laville, M Chaker, Mohamad Sabsabi, T W Johnston, O Barthelemy, Francois VidalAbstract:Quantitative analysis of aluminum and copper alloys by means of Laser-induced plasma spectroscopy (LIPS) has been investigated for three representative Laser Pulse Durations (80 fs, 2 ps, and 270 ps). The experiments were carried out in air at atmospheric pressure with a constant energy density of 20 J/cm2. Because the decay rate of the spectral emission depends on the Laser Pulse Duration, the optimum detection requires an optimization of the temporal gating acquisition parameters. LIPS calibration (sensitivity and nonlinearity) and the limit of detection (LOD) are discussed in detail. While the LOD of minor elements embedded in alloy samples obtained by sub-picosecond or sub-nanosecond Laser Pulses are both time and element dependent, provided an appropriate temporal window is chosen, the optimum LODs (several parts per million (ppm)) prove to be independent of the Laser Pulse Duration. Finally, it is found that for elements such as those detected here, gated LIPS spectra using picosecond or sub-picosecond Laser Pulses provide much better LOD values than non-gated spectra.
Jacques Faerber - One of the best experts on this subject based on the ideXlab platform.
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role of Laser Pulse Duration and gas pressure in deposition of aln thin films
Journal of Applied Physics, 2001Co-Authors: E Gyorgy, C Fotakis, C Ristoscu, I N Mihailescu, Argyro Klini, N A Vainos, C Ghica, G Schmerber, Jacques FaerberAbstract:We investigated the relative merits and limits of Pulsed Laser deposition from AlN targets in vacuum and low-pressure nitrogen in obtaining stoichiometric and crystalline aluminum nitride thin films. We used two UV excimer Laser sources (λ=248 nm): a nanosecond system (τFWHM=30 ns) and, a subpicosecond (τFWHM=450 fs) system. The obtained structures were characterized by x-ray diffraction, electron microscopy in cross section, selected area electron diffraction, and profilometry. We demonstrated that the best results are obtained with the sub-ps Laser source in vacuum and in low pressure nitrogen when the AlN thin films are very pure, crystalline, clearly exhibiting a tendency to epitaxy. Metallic Al is present in the films deposited with the ns Laser source. We believe this is an effect of the gradual decomposition of AlN inside the crater on the target surface under multiPulse Laser irradiation.
