Showing papers by "Richard E. Russo published in 2010"

Laser-induced breakdown spectroscopy in industrial and security applications

Abstract: Laser-induced breakdown spectroscopy (LIBS) offers rapid, localized chemical analysis of solid or liquid materials with high spatial resolution in lateral and depth profiling, without the need for sample preparation. Principal component analysis and partial least squares algorithms were applied to identify a variety of complex organic and inorganic samples. This work illustrates how LIBS analyzers can answer a multitude of real-world needs for rapid analysis, such as determination of lead in paint and children's toys, analysis of electronic and solder materials, quality control of fiberglass panels, discrimination of coffee beans from different vendors, and identification of generic versus brand-name drugs. Lateral and depth profiling was performed on children's toys and paint layers. Traditional one-element calibration or multivariate chemometric procedures were applied for elemental quantification, from single laser shot determination of metal traces at ~10 μg/g to determination of halogens at 90 μg/g using 50-shot spectral accumulation. The effectiveness of LIBS for security applications was demonstrated in the field by testing the 50-m standoff LIBS rasterizing detector.

Optical far- and near-field femtosecond laser ablation of Si for nanoscale chemical analysis.

Abstract: Extending spatial resolution in laser-based chemical analysis to the nanoscale becomes increasingly important as nanoscience and nanotechnology develop. Implementation of femtosecond laser pulses arises as a basic strategy for increasing resolution since it is associated with spatially localized material damage. In this work we study femtosecond laser far- and near-field processing of silicon (Si) at two distinct wavelengths (400 and 800 nm), for nanoscale chemical analysis. By tightly focusing femtosecond laser beams in the far-field, we were able to produce sub-micrometer craters. In order to further reduce the crater size, similar experiments were performed in the near-field through sub-wavelength apertures, resulting in the formation of sub-30-nm craters. Laser-induced breakdown spectroscopy (LIBS) was used for chemical analysis with a goal to identify the minimum crater size from which spectral emission could be measured. Emission from sub-micrometer craters (full width at half maximum) was possible, which are among the smallest ever reported for femtosecond LIBS.

Ultrafast thin-film laser-induced breakdown spectroscopy of doped oxides

Abstract: Single-shot femtosecond laser induced breakdown spectroscopy (LIBS) has been shown to be an effective means of detecting heavy metal dopants in porous thin films. Traditional LIBS analysis of trace dopants in modern painted surfaces or TiO2 films is difficult due to the broad noisy spectra of the titanium constituent and interference due to the substrate material. Femtosecond laser pulses provide excellent ablation of the target material with little damage to the underlying substrate. In this study a Ti:sapphire femtosecond laser pulse operated at 800 and 266 nm wavelengths and an Nd:YAG nanosecond laser operated at 266 nm were used to ablate 0.15-15 μm films of TiO2 doped with varying amounts of MgO. This application shows excellent detection of Mg down to 60 ppm with little interference by the substrate material.

Analysis of nanopatterning through near field effects with femtosecond and nanosecond lasers on semiconducting and metallic targets

Abstract: A systematic study was conducted to understand the size and shape of nanopatterns generated on selected semiconducting (Si and Ge) and metallic (Cr, Cu, and Ag) targets under different laser pulse durations, laser energies, and number of laser pulses. Based on the experimental results, femtosecond laser pulses, compared with nanosecond laser pulses, provide lower damage thresholds to the targets but higher damage thresholds to the near field scanning optical microscope (NSOM) probes at the wavelength (∼400–410 nm) studied. Furthermore, the resulting nanopatterns showed a significant dependence on the optical properties (i.e., absorption coefficient and surface reflectivity) of the target material. By comparing the obtained experimental results, we conclude that the optical energy transport from the NSOM probe to the target dominates the pattern generation when femtosecond laser is applied to the NSOM system. When nanosecond laser is applied, both the thermal and optical energy transported from the NSOM pr...

Separation of Copper Isotopes in the Laser Plume

Abstract: Isotopic separation was observed during ablation of standard copper samples by a nanosecond Nd‐YAG laser and a femtosecond Ti:sapphire laser at 266 nm A time‐of‐flight mass spectrometer, orthogonal to the direction of the laser plume, was used to measure the isotopic composition of the plasma A voltage was applied to the pulser at different delay times after the laser was ired in order to obtain a temporal profile as the plume expanded The fraction of 63Cu in the plasma detected by the mass spectrometer reaches a maximum of 083 at 6 US and 3 μs after the laser is ired for the nanosecond and femtosecond lasers respectively, before falling back to the natural abundance ratio of 069 As reported in the literature, the ion peaks are centered at two different delay times, representing fast and slow ion energy distributions A mechanism based on the electric ield interactions between the electrons and ions is proposed to explain the separation of isotopes in the plume

Laser-Induced Breakdown Spectroscopy in Industrial and Security Applications

Abstract: Laser-induced breakdown spectroscopy (LIBS) offers rapid, localized chemical analysis of solid or liquid materials with high spatial resolution in lateral and depth profiling, without the need for sample preparation. Principal component analysis and partial least squares algorithms were applied to identify a variety of complex organic and inorganic samples. This work illustrates how LIBS analyzers can answer a multitude of real-world needs for rapid analysis, such as determination of lead in paint and children's toys, analysis of electronic and solder materials, quality control of fiberglass panels, discrimination of coffee beans from different vendors, and identification of generic versus brand-name drugs. Lateral and depth profiling was performed on children's toys and paint layers. Traditional one-element calibration or multivariate chemometric procedures were applied for elemental quantification, from single laser shot determination of metal traces at ~10 μg/g to determination of halogens at 90 μg/g using 50-shot spectral accumulation. The effectiveness of LIBS for security applications was demonstrated in the field by testing the 50-m standoff LIBS rasterizing detector.

Nanostructures, assembling method for nanowires, and device assembled from nanowires

Abstract: PROBLEM TO BE SOLVED: To provide one-dimensional nanostructures having diameters along a vertical axis wherein the diameters do not change nearly 10% or more at a section showing the maximum diameter change and the maximum diameters of less than approximately 200 nm, regarding substantially crystalline nanowire structures. SOLUTION: The one-dimensional nanostructures have the uniform diameters of less than approximately 200 nm. The new nanostructures called as "nanowires" include single-crystalline homostructures as well as heterostructures of two single-crystalline materials having different chemical compositions. The resulting heterostructures similarly become single crystals since the single-crystalline materials are used for forming the heterostructures. The nanowire heterostructures are generally based on a semiconducting wire wherein the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire including different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN). COPYRIGHT: (C)2011,JPO&INPIT

Method of fabricating nanostructures and nanowires and device fabricated therefrom

Abstract: PROBLEM TO BE SOLVED: To provide a method of fabricating nanostructures and nanowires and a device fabricated therefrom. SOLUTION: A one-dimensional nanostructure has a uniform diameter of less than approximately 200 nm. Such new nanostructure which is called as "a nanowire" includes a single-crystal homostructure as well as heterostructure of at least two single crystal materials having different chemical compositions. Because the single crystal material is used to form the heterostructure, the resultant heterostructure may be a single crystal as well. The nanowire heterostructure is generally based on a semiconducting wire in which the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire that comprises different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN). COPYRIGHT: (C)2010,JPO&INPIT