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Molecular gas species for gas cluster ion beams (GCIBs), such as carbon dioxide and water, were examined with a range of beam energies and cluster sizes to compare with the "universal relation" of the sputter yield, Y, per cluster atom against incident beam energy, E, per cluster atom of Arn cluster beam using Irganox 1010. In this work, we compare Arn, (CO2)n, and (H2O)n gas clusters to the universal equations for Arn clusters. To discuss molecular gas species for GCIBs, energy per nucleon (E/N) needs to replace energy per atom. We monitored sputter rate, depth resolution, and secondary ion yield as a function of the beam parameters: gas species, beam energy, and cluster size. (H2O)n GCIB shows reduced sputter rates and improved depth resolution with high sensitivity compared to Arn and (CO2)n GCIBs. These initial results indicate the potential to achieve high-depth resolution with high sensitivity and suggest that (H2O)n cluster ion beam has the potential to play a significant role in surface analysis techniques with organic materials. Results also show that no single set of conditions will provide the "best gas cluster ion beam" for all applications. However, it is possible to choose a set of conditions that will be more or less optimal depending on the experimental goals, such as maximizing the sputter rate, depth resolution, and molecular ion yield. In this work, we recommend the following three guidelines for GCIB users to set their own conditions: (1) to maximize the sputter rate, select a smaller cluster (higher E/N), but be aware that this will increase fragmentation and reduce molecular ion yield; (2) to maximize the depth resolution, select a larger cluster (lower E/N), and use (H2O)n GCIB, if possible; and (3) to maximize the molecular ion signal, use the highest beam energy available, and select a cluster with 0.15–0.25 eV/nucleon for Ar and (CO2)n GCIBs or around 0.1 eV/nucleon if using (H2O)n GCIB. These results are valid for XPS, SIMS, and any technique that utilizes GCIBs. [ABSTRACT FROM AUTHOR]

Since carbon nanotubes and onions were discovered, many methods have been proposed for their production. For applications the main requirements are low capital cost, high purity of the produced material, simplicity of technique, and its potential for scale up. Recently a cathodic arc between two graphitic electrodes immersed in liquids has been demonstrated to be a simple method to produce carbon nanoparticles such as nanotubes and onions. In this paper high-resolution transmission electron microscopy is employed to examine the shape of the nanoparticles and the purity of the final material produced under various conditions. In this study we have used an arc discharge in two different liquids—liquid nitrogen and distilled water—and we have changed the grade of the carbon electrodes. The variety in structure, shape, and size of the produced particles is discussed in line with a model proposed to describe the physical process. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A simple method to fabricate high-quality nanoparticles including spherical carbon onions and elongated fullerene-like nanoparticles similar to nanotubes in large quantities without the use of vacuum equipment is reported. The nanoparticles are obtained in the form of floating powder on the water surface following an arc discharge between two graphite electrodes submerged in water. High-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy images confirm the presence of spherical carbon onions with diameters ranging from 4 to 36 nm. The specific surface area of the floating powder was found to be very large, 984.3 m²/g, indicating that the material is promising for gas storage. From the surface area measurements, the mean particle diameter was calculated to be 3.7 nm. This value is close to the lower limit of the carbon onions observed in HRTEM. However, closer HRTEM observations also reveal that some carbon onions are not well crystallized. The large specific surface area can be attributed to the "surface roughness" induced by the defective nature of the carbon onion shells. To explain the formation mechanism of the carbon onions, a model of arc discharge in water with two quenching zones is proposed: (1) the presence of ion current conducive for elongated nanoparticles growth and (2) the absence of ion current for isotropic growth of carbon onions. Based on this model, we propose that the physical characteristics of the product can be controlled. [ABSTRACT FROM AUTHOR]

Detailed magnetic properties of fine-grained doubly oriented Si steel of 0.25-0.35 mm in thickness are discussed. The doubly oriented Si steel sheets with grains of about 0.5 mm in diameter showed about 35% smaller core losses than the previously studied coarse-grained materials at the commercial frequency of 60 Hz.

To clarify the orientational memory site in the hydrogen disproportionation desorption recombination process of Nd[sub 2]Fe[sub 14]B-based anisotropic magnets, high resolution transmission electron microscopy (HRTEM) characterization of hydrogen disproportionated structure of Nd[sub 13.0]Fe[sub 67.9]Co[sub 11.0]Ga[sub 1.0]Zr[sub 0.1]B[sub 7.0] has been performed. In particular, crystallographic orientations of disproportionated products relative to that of parent or original Nd[sub 2]Fe[sub 14]B have been carefully analyzed using partially disproportionated samples. No apparent orientational coherency exists between the disproportionated products of α-Fe, Fe[sub 2]B, and NdH[sub 2] and the parent Nd[sub 2]Fe[sub 14]B. However, nanoscale Nd[sub 2]Fe[sub 14]B particles of 10 to 100 nm in diameter have been detected by HRTEM to be densely present within the disproportionated mixture. Lattice fringe observation has also revealed that the crystallographic axes of the Nd[sub 2]Fe[sub 14]B particles are nearly parallel to those of the original Nd[sub 2]Fe[sub 14]B. It is thus suggested that these Nd[sub 2]Fe[sub 14]B particles be the orientational memory site upon the recombination, which recovers the original orientation leading to the anisotropy formation. [ABSTRACT FROM AUTHOR]

Reports on the growth and characterization of indium arsenide/In[sub1-x]Al[subx]As strained-layer superlattices on gallium arsenide. Growth of the strained-layer superlattices; X-ray diffraction measurements of the superlattices; Measurements conducted to evaluate the strain-induced effects on band structures.

Investigates the effects of indium[sub0.2]aluminum[sub0.8]arsenic buffer layers on the lattice distortions of strained layer superlattices (SLS) by x-ray diffraction. Methods to superimpose the SLS on the large lattice mismatched substrate without defect structures near the interfaces; Determination of alloy compositions and layer thicknesses; Summary of observed and calculated intensities around the reflection and four fitting parameters.

Presents a study which investigated finite-size effects on Raman scattering by longitudinal acoustic (LA) and longitudinal optic phonon (LO) modes in gallium arsenide-aluminum arsenide superlattices. Comparison of the experimental results with theoretical results; Differences between finite-size effects on folded LA phonon modes and confined LO phonon modes; Measurement of Raman scattering.

Presents a photoluminescence study of indium[subx] aluminum[sub1-x] arsenide-gallium arsenide strained layer superlattices. Evaluation of the effects of biaxial strain in the planes perpendicular on the superlattice direction; Method used to interpret the strain effects of band structures; Ways in which strain effects were evaluated.

Studies the lattice-mismatch strains in strained-layer superlattices grown by molecular beam epitaxy. Results and discussion; Conclusion.

Deals with a study that investigated plasma hydrogenation of laser-crystallized and amorphized films. Determination of the hydrogen concentration; Analysis of defect density and hydrogen concentration; Relation between the reduction of defects and the change in the optical properties in laser-amorphized silicon films.