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Spectroscopic analysis and structural diagnostic of Selenium nanoparticles prepared by LIP
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A spectroscopic study on laser-produced tin plasma utilizing the optical emission spectroscopy (OES) technique is presented. Plasma is produced from a solid tin target irradiated with pulsed laser in room environment. Electron temperature is determined at different laser peak powers from the ratio of line intensities, while electron density is deduced from Saha-Boltzmann equation. A limited number of suitable tin lines are detected, and the effect of the laser peak power on the intensity of emission lines is discussed. Electron temperatures are measured in the range of 0.36 eV–0.44 eV with electron densities of the order 1017 cm–3 as the laser peak power is varied from 11 MW to 22 MW.
In this work, the optical emission spectroscopy was used to analyze the parameters of dc discharge plasma in dual tin–copper co-sputtering system. Discharge power of 120 W and gas pressure ranging in 0.3–0.8 mbar were considered. The emission line profiles of tin–copper alloy were experimentally observed and used to determine the electron temperature in plasma using the Boltzmann plots method, whereas the electron density was determined from the Stark broadening. The variation of electron temperature and electron density as functions of nitrogen pressure was also studied.
The acoustic emission signal of laser plasma shock wave, which comes into being when femtosecond laser ablates pure Cu, Fe, and Al target material, has been detected by using the fiber Fabry-Perot (F-P) acoustic emission sensing probe. The spectrum characters of the acoustic emission signals for three kinds of materials have been analyzed and studied by using Fourier transform. The results show that the frequencies of the acoustic emission signals detected from the three kinds of materials are different. Meanwhile, the frequencies are almost identical for the same materials under different ablation energies and detection ranges. Certainly, the amplitudes of the spectral character of the three materials show a fixed pattern. The experimental results and methods suggest a potential application of the plasma shock wave on-line measurement based on the femtosecond laser ablating target by using the fiber F-P acoustic emission sensor probe.
In this work, the characteristics of the CdS/Si structure produced by plasma-induced bonding technique were studied. The produced structure was an asymmetric heterojunction consisting of n-type CdS on a p-type silicon substrate. The Si substrate and CdS sample were bonded by subjecting them to the plasma formed between two electrodes. The measurements included the structural and electrical characteristics. The typical spectral responsivity within the range 400–800 nm and the maximum value is at 577 nm. With dark current of 6 μA, maximum reverse bias current of 670 μA and ideality factor of 3.5, the results explained better characteristics than those of the same heterojunction produced by other deposition techniques.
We have studied the effects of the laser fluence on the characteristics of ZnO nanoparticles produced by pulsed laser ablation (PLA) of Zn plate in acetone. The beam of a Q-switched Nd:YAG laser of 1064 wavelength at 7 ns pulse width and different fluencies was employed to produce nanoparticles. The ZnO nanoparticles were found to be hexagonal. The size distribution of generated nanoparticles is increased by increasing the laser fluence. The production rate of nanoparticles is increased with increasing the laser fluence. ZnO nanoparticles were formed with spherical shape. The bandgap energy of nanoparticles is calculated to be 3.59–3.89 eV. In this range of ZnO nanoparticle size, photoluminescence spectrum exhibits two peaks due to bandgap transition and defect levels.
Laser Induced Breakdown Spectroscopy (LIBS) is an emerging technique for determining elemental composition. With the ability to analyse solids, liquids and gases with little or no sample preparation, it is more versatile than conventional methods and is ideal for on-site analysis. This is a comprehensive reference explaining the fundamentals of the LIBS phenomenon, its history and its fascinating applications across eighteen chapters written by recognized leaders in the field. Over 300 illustrations aid understanding. This book will be of significant interest to researchers in chemical and materials analysis within academia and industry. © A. Miziolek, V. Palleschi and I. Schechter 2006 and Cambridge University Press, 2009. All rights reserved.
Early in the next century, several space missions are planned with the goal of landing craft on asteroids, comets, the Moon, and Mars. To increase the scientific return of these missions, new methods are needed to provide (1) significantly more analyses per mission lifetime, and (2) expanded analytical capabilities. One method that has the potential to meet both of these needs for the elemental analysis of geological samples is laser-induced breakdown spectroscopy (LIBS), These capabilities are possible because the laser plasma provides rapid analysis and the laser pulse can be focused on a remotely located sample to perform a stand-off measurement. Stand-off is defined as a distance up to 20 m between the target and laser. Here we present the results of a characterization of LIES for the stand-off analysis of soils at reduced air pressures and in a simulated Martian atmosphere (5-7 torr pressure of CO2) showing the feasibility of LIES for space exploration. For example, it is demonstrated that an analytically useful laser plasma can be generated at distances up to 19 m by using only 35 mJ/pulse from a compact laser. Some characteristics of the laser plasma at reduced pressure were also investigated. Temporally and spectrally resolved imaging show ed significant changes in the plasma as the pressure was reduced and also showed that the analyte signals and mass ablated from a target were strongly dependent on pressure, As the pressure decreased from 590 torr to the 40-100 torr range, the signals increased by a factor of about 3-4, and as the pressure was further reduced the signals decreased. This behavior can be explained by pressure-dependent changes in the mass of material vaporized and the frequency of collisions between species in the plasma. Changes in the temperature and the electron density of the plasmas with pressure were also examined and detection limits for selected elements were determined.
This paper discusses the use of lasers in analytical atomic spectrometry. Following a brief discussion on the properties of lasers that attract analytical atomic spectroscopists, the major uses of lasers, i.e., in laser excited atomic fluorescence, laser-enhanced ionization, laser-induced breakdown emission and laser sampling are described, particularly its application to real samples. A very brief description of theory or basic principles, laser used in experimental set up and selected and representative applications are presented. Finally, the potential future of the laser in analytical atomic spectrometry will be discussed.1 Presented, in part, at Pittcon 97, Atlanta, Georgia, 16–21 March, 1997