bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radio Frequency Heating Coils for Shock Wave Experiments
Authors: Chen George Q. , Ahrens Thomas J. 
Published: April 2011

ABSTRACTRadio-frequency eddy current heating of metallic samples in shock wave, ultrasonic and diamond anvil apparatus provides a methodology for obtaining hot samples or hot metallic gaskets (containing a sample) and yet not heating the entire target, ultrasonic assembly or diamond cell. Analysis of a previous design of a radio-frequency (∼0.5 MHz) coil demonstrated that the center of 13 mm diameter shock wave experiment sample discs were underheated and the experimental temperatures achieved resulted from conduction of heat from the overheated sample edges relative to the center of the sample. We show, using the Biot-Savant law, that the ratio of magnetic field in the center to that at the edge of the sample, f, can be maximized to a value of f=1.8, by decreasing the radius of the heater coil, relative to the 13 mm diameter of sample. A simple analysis provides the thermal gradient across the sample thickness. An electric skin depth for iron of ∼1 mm for the 0.45 MHz frequency of the heater power supply of our system is obtained. This leads to a maximum temperature gradient of ∼52 K over the 4 mm thickness of the shock wave sample discs.
Study of the Local Atomic order in Si/C/N Nanopowders by X-ray Photoelectron Spectroscopy
Authors: Gheorghiu-de la Rocque A. , Dufour G. , Bonnefont P. A. , Sénémaud C. , Cauchetier M. 
Published: April 2011

ABSTRACTA study by X-ray photoelectron spectroscopy (XPS) of the local atomic environment in laser-synthetized Si/C/N nanopowders is presented. The Si 2p, C Is, and N 1s core levels as well as the valence band distribution are investigated. The attention is focused on samples with C/N atomic ratio around 0.6 which exhibit interesting properties concerning annealing treatments. The presence of C-N bonds after 1500°C annealed samples is evidenced.
Rheological behavior of an aluminum nitride nanoparticle suspension in Poly(amic acid)-nmp system
Authors: Chen Xiaohe , Gonsalves Kenneth , Rounds R. S. 
Published: April 2011

ABSTRACTPreliminary rheological characterizations of aluminum nitride (AIN) nanoparticle suspensions in nonaqueous Newtonian fluid media, NMP and NMP/poly(amic acid) solutions, reveal marked differences in viscoelastic behavior, at relatively low dispersed phase volume fractions. Dynamic mechanical and steady shear measurements provide experimental evidence of the effective interparticle and polymer/particle interactions in a dispersion process of nonoxide nanoparticles for ceramic/polymer nanocomposites. The rheological nature of the nanoparticle suspensions corresponds to interparticle physicochemical interactions that have been previously concluded and discussed.
Surface controlled nanospheres as drug carriers for intravenous and intranasal administration
Authors: Gref R. , Quellec P. , Dellacherie E. , Tobio M. , Alonso M. J. 
Published: April 2011

ABSTRACTThe arival on the market of new therapeutic and antigenic molecules requires the development of appropriate delivery systems. The design of injectable nanoparticulate drug caniers invisible to the mononuclear phagocyte system is a major challenge. Also, overcoming mucosa baniers, such as the nasal one, using biodegradable nanospheres is another strategy still to be explored. These routes of administration require nanoparticulate systems with optimized surface properties. We investigated the ability of polyethylene glycol (PEG)-coated nanospheres made of amphiphilic diblock copolymers to achieve these goals. After an optimization of the nanosphere surface properties, we studied the possibility of entrapping macromolecules within the PEG-coated nanospheres. Results showed that it is possible to encapsulate a model protein, human serum albumin (HSA) within monodisperse nanospheres of a mean diameter of about 200 nm, reaching loadings as high as 9% (w/w). Moreover, these nanospheres showed excellent abilities for the transport of a model antigen, tetanus toxoid (Tr) through the nasal mucosa.
Nanostructured powders: a new class of materials for forming high performance particulate coatings
Authors: Skandan Ganesh 
Published: April 2011

ABSTRACTNanostructured powders, with particle sizes in the range 1 to 100 nm, have shown great promise in the forming of advanced films and coatings for a variety of applications including tribological, high surface area supports for catalysts, chemical gas sensors, and optoelectronics. This paper is a summary of two major classes of powder synthesis techniques: (1) precipitation from aqueous salt solutions, and (2) condensation from vapor phase. The solution approach leads to powder particles that are spherical shells consisting of nanograins. The powder is milled with melting point lowering compounds and reagglomerated to make it suitable for thermal spraying. In contrast, the vapor condensation approach yields powder particles that are discrete, and loosely agglomerated. In a variation of the process, the heated clusters or nanoparticles are allowed to sinter on a heated substrate, forming porous or dense coatings. Films/coatings with thicknesses between 0.5 μm and 20.0 μm at rates in excess of 1 μm/min. are formed by thein situdeposition process. The synthesis techniques, powder and coating characteristics, and applications of the technologies, are described in this paper.
A Metastable-atom Deexcitation Spectroscopy (MDS) study on the First Atomic Layer of a Polycrystalline Titanium Surface
Authors: Kurahashi M. , Yamauchi Y. 
Published: April 2011

ABSTRACTThe oxygen adsorption on a polycrystalline titanium surface at room temperature has been studied by MDS in conjunction with UPS and AES. MDS and UPS spectra were measured using a pulsed-dischaxge-type metastable helium atom source which we have newly developed. FRom the analysis of the measured spectra, we found the following about the local density of states (LDOS) of the oxygen-adsorbed titanium surface: (1) With increasing oxygen exposure at 0-2 L, the LDOS on the first atomic layer (SDOS) at 0-1 eV below the Fermi level (EF) decreases more steeply than that of deeper layers. (2) The SDOS at 5–8 eV below EF remains small at 0-2 L, and begins to increase at ca. 2 L while the LDOS of subsurface layer increases first. We discuss the positions of adsorbed oxygen atoms based on these results.
Effect of surface modification on the electrical properties of TiO2 and SnO2 nanopowders
Authors: Chancel Fabienne , Tribout Jérôme , Baraton Marie-Isabelle 
Published: April 2011

ABSTRACTThe surface modification of titania and tin dioxide nanopowders by hexamethyldisilazane and hexamethyldisiloxane grafting has been followed in situ by FT-IR spectroscopy. A grafting mechanism is proposed for both compounds and the formation of new surface species is discussed. Since TiO2 and SnO2 are widely used in chemical gas sensors due to their electrical properties, the respective behaviors of the non-grafted and grafted samples in reducing (CO) environment as well as the humidity effects are compared. Because the transmitted IR energy depends on the concentration of the free carriers, a correlation between the electrical conductivity variation and the perturbation of the IR spectra is attempted.
Oxygen adsorption on tin oxide nanosized powders characterized by FTIR spectrometry and Relation with the sensor properties
Authors: Tribout J. , Chancel F. , Baraton M.-I. , Ferkel H. , Riehemann W. 
Published: April 2011

ABSTRACTThe surfaces of two tin oxide nanosized powders synthesized by laser evaporation and presenting different average grain sizes were studied by Fourier transform infrared spectrometry. The oxygen adsorption onto activated and oxidized surfaces appeared to be dependent upon the grain size. Moreover, the nature of surface acidic sites probed by pyridine was shown to be dependent on the oxidizing treatment. A simultaneous study of the infrared energy variations and the spectrum perturbations when CO and mixtures of CO and O2 were in contact with the SnO2 samples, showed both the formation of CO2 and the CO reducing effect. The need of an oxygen environment for the surface recovery was clearly brought in evidence as well as the importance of the temperature in the CO sensing mechanism.
Radiation Effect on the Viscosity of the Simple B2O3 Glasses
Authors: Barbu A. , Jaskierowicz G. 
Published: April 2011

ABSTRACTThe creep velocity of B203 glass fibers under irradiation with 2.5 MeV electrons at low flux ( around 5 1013 e-cm−2s−1) has been studied versus temperature. As under very high energy heavy ions irradiation (1.6 GeV argon), the viscosity is drastically reduced below 300°C. An important difference between the two kinds of irradiation is the occurrence of a compaction phenomenon at the beginning of electron irradiation experiments. The results can be understood by assuming two totally different mechanisms: a relaxation driven by melting of the glass along the path of the ions for very high energy heavy ion irradiations and a relaxation driven by individual radiation induced points defects for high energy electron irradiations.
Hrtem and Eels Studies of Reacted Materials From Caf2 by Electron Beam Irradiation
Authors: Kogure T. , saiki K. , Konno M. , Kamino T. 
Published: April 2011

ABSTRACTThe change of calcium fluoride (CaF2) by electron beam irradiation has been investigated in TEMs operated at 200 kV. By irradiation fluorine is desorbed rapidly from CaF2 crystal. Although plasmon peaks in EELS spectra suggest the formation of Ca metal, no evidence for the existence of Ca metal is found in electron diffraction pattern or HRTEM images. This is due to perfect topotactic formation of Ca metal from CaF2 with a similar crystal structure and closely similar lattice parameters. Irradiation also forms amorphous material near the edge of Ca/CaF2 and randomly oriented CaO crystallites grow from the amorphous material. This amorphous material is regarded as hydroxide formed through the reaction of Ca and water, considering the residual gas composition and the formation rate of the material.
Thermal Behaviour of Implanted Nitrogen and Accumulated Hydrogen in Titanium
Authors: Soltani-Farshi M. , Baumann H. , Rück D. , Walter G. , Bethge K. 
Published: April 2011

ABSTRACTThe influence of nitrogen ion implantation on the hydrogen accumulation in titanium was investigated as function of sample temperature and ion fluence. 150 keV nitrogen (15N) ions were implanted at different sample temperatures up to 700°C with fluences ranging from 1 × 1017 to 1 × 1018 ions/cm2. The amount of accumulated hydrogen and its depth distribution was measured quantitatively with the 15N depth profiling method. The implanted 15N depth profiles were measured by the reverse reaction 15N(p, αγ)12C at 429 keV. The binary phases of the implanted nitrogen with titanium are detected by grazing incidence x-ray diffraction. The results are compared with those obtained for samples implanted at RT and subsequently thermally treated.
Numerical Modeling and Experimental Measurements of Pulsed Ion Beam Surface Treatment
Authors: Thompson Michael O. , Renk T. J. 
Published: April 2011

ABSTRACTPulsed ion beam treatment of materials provides an attractive alternative to pulsed laser processing for near surface modification of semiconductors, metals and polymers. The transfer of energy to the sample occurs by electronic and nuclear stopping over depths extending to several microns depending on ion species and voltage. A numerical code for modeling the melt and solidification behavior of materials under ion beam processing has been developed. The code and parameter extraction procedures were validated experimentally by comparing simulations with experimental measurements of the melt duration in silicon. The sensitivity of the melt behavior to variations in the beam properties was also investigated. The quiescent nature of the melt was confirmed by measurements of the diffusion of arsenic in the melt. These results demonstrate that simulations of the ion beam treatment can quantitatively match experimental results with no adjustable parameters.
Nanocrystal Growth at High Dose Rates in Negative Copper-Ion Implantation Into Insulators
Authors: Kishimoto N. , Gritsyna V. T. , Takeda Y. , Lee C. G. , Umeda N. , Saito T. 
Published: April 2011

ABSTRACTNanoparticles of Cu were fabricated by negative-ion implantation, leading to spontaneous formation at high beam fluxes. Negative ions, alleviating surface charging, exhibit significant merits in carrying out low-energy implantation at high dose rates. The kinetic processes were studied by measuring dose-rate dependence of colloid formation and resultant optical properties. Negative-Cu ions of 60 keV were implanted into silica glasses at high-current densities, up to 260 μA/cm2, fixing the total dose at 3.0 × 1016 ions/cm2. Spherical nanocrystals of Cu atoms formed within a narrow region, near the projectile range of Cu ions. Simultaneously, much smaller particles spread out beyond a depleted zone, deeper than the projectile range. The nanocrystal growth and optical properties were greatly dependent on the dose rate and the specimen boundary condition. The growth process is explained by a droplet-model based on surface tension and radiation-induced diffusion. Beam-surface interactions also play an important role in the mass transport from the beam flux to the interior solid.
Advances in Ion and Laser Beam Technology: Achievements of Japanese Government and University Projects
Authors: Yamada Isao 
Published: April 2011

ABSTRACTThis paper reviews recent R&D activity in advanced beam technologies funded by MITI and JST. A large-scale national project known as AMMTRA (Advanced Material-Processing and Machining Technology Research Association) funded by MITI has made a significant contribution to industrial applications of beam processing by developing high density ion and laser beam equipment. A subsequent program, the ACTA (Advanced Chemical Processing Technology Research Association) project involves development of multi-beam deposition systems for metal and dielectric materials formation including several systems which combine ion and laser beams, ion beams and CVD and plasma, and laser beams with sputtering. NEDO Proposal Based Project and JST (The Japan Science and Technology Corporation)-Exploitation and Application Study Project are fundamentally aimed to transfer technology from university to industry. Research in gas cluster ion beam technology is currently being conducted in the following areas: (i) shallow ion implantation for 0.1 μ m PMOS junction formation, (ii) high rate etching and smoothing for Si, diamond, SiC and metal oxide films and (iii) thin film depositions for optical filter and transparent conductive film. The gas cluster ion beam processes are discussed in comparison with traditional ion beam processing methods which are presently limited by available atomic and molecular ion beams.
Photo Modified Growth of GaAs by Chemical Beam Epitaxy
Authors: Jothilingam R. , Farrell T. , Joyce T.B. , Goodhew P.J. 
Published: April 2011

AbstractWe report the photo modified growth of GaAs by chemical beam epitaxy at substrate temperatures in the range 335 to 670°C using triethygallium (TEG) and arsine. A mercury-xenon lamp (electrical power 200 W) provided the irradiation for the photoassisted growth. The growth was monitored in real time by laser reflectometry (LR) using a 670 nm semiconductor laser, and the optically determined growth rate agreed with that obtained from the layer thickness measured by cross sectional transmission electron microscopy. The observed photo-enhancement of the growth rate at low substrate temperatures and inhibition at high substrate temperatures is thermal in origin, consistent with raising the substrate temperature by 10±3°C. Cross sectional transmission electron microscopy showed that the photoassisted layers are essentially free from dislocations
Engineering Dislocation Dynamics in Inx(AlyGa1−y)1−xP Graded Buffers Grown on Gap by Movpe
Authors: Kim A.Y. , Fitzgerald E.A. 
Published: April 2011

AbstractTo engineer high-quality Inx(AlyGa1−y)1−x P/Ga1−xP graded buffers, we have explored the effects of graded buffer design and MOVPE growth conditions on material quality. We demonstrate that surface roughness causes threading dislocation density (TDD) to increase with continued grading: dislocations and roughness interact in a recursive, escalating cycle to form pileups that cause increasing roughness and dislocation nucleation. Experiments show that V/III ratio, temperature, and grading rate can be used to control dislocation dynamics and surface roughness in InxGa1−xP graded buffers. Control of these parameters individually has resulted in x = 0.34 graded buffers with TDD = 5 × 106 cm−2and roughness = 15 nm and a simple optimization has resulted in TDD = 3 × 106 cm −2and roughness = 10 un. Our most recent work has focused on more sophisticated optimization and the incorporation of aluminum for x > 0.20 to keep the graded buffer completely transparent above 545 nm. Given our results, we expect to achieve transparent, device-quality Inx(AlyGa1−y)1−x P/GaP graded buffers with TDD < 106 cm−2
Hydrogenation and Defect Creation in GaAs-Based Devices During High Density Plasma Processing
Authors: Maeda T. , Lee J. W. , Abernathy C. R. , Pearton S. J. , Ren F. , Constantine C. , Shul R. J. 
Published: April 2011

AbstractThe effects of Inductively Coupled Plasma (ICP) and Electron Cyclotron Resonance (ECR) H2 plasmas on GaAs metal semiconductor field effect transistors (MESFETs), high electron mobility transistors (HEMTs) and heterojunction bipolar transistors (HBTs) have been measured as a function of ion flux, ion energy and process pressure. The chemical effects of hydrogenation have been compared to direct physical bombardment by Ar plasmas under the same conditions. Si dopant passivation in MESFETs and HEMTs and C base-dopant passivation in HBTs produces much larger changes in sheet resistance, breakdown voltage and device gain or transconductance than Ar ion bombardment and suggests that H2-containing plasma chemistries (CH4/H2 for semiconductor etching, SiH4 for dielectric deposition, CHF3 for dielectric etching) should be avoided, or at least the exposure of the surface minimized. In some cases the device degradation is less for higher source power conditions, due to the suppression of cathode dc self-bias and hence ion energy.
Athermal Annealing of Silicon
Authors: Grun J. , Manka C.K. , Hoffman C. A. , Meyer J. R. , Glembocki O. J. , Qadri S. B. , Skelton E. F. , Donnelly D. , Covington B. 
Published: April 2011

AbstractWe experimentally demonstrate the annealing and electrical activation of doped silicon without the direct application of heat as in conventional thermal annealing or pulsed laser annealing. 25 × 25 × 3 mm samples of silicon doped by neutron transmutation were irradiated with a short pulse from a 1.06-micron laser. The few joule laser pulse was focused to mm-diameter surface spot which resulted in high power (∼ 1011W/cm2) capable of launching shocks into the entire sample. In a few instances the entire silicon slab, including regionsfar outside the illuminated spot, was annealed and electrically activated. In the annealed samples electrical activation of donors throughout the slab, measured with a four-point probe, was uniform and comparable to that of thermally annealed control samples. Far-infrared spectroscopy and Hall measurements also showed that the donor species was activated and Raman spectroscopy demonstrated marked improvement in the crystal structure. We conjecture that the annealing was caused by the mechanical energy that was launched into the slab by the laser pulse. Results of experiments on an ion-implanted silicon sample are also discussed.
Evidence of Defect Migration and Clustering in MeV Heavy Ion Damaged Silicon
Authors: Mohapatra Y.N. , Girl P.K. 
Published: April 2011

AbstractWe have studied electrically active defects created by MeV heavy ion implantation in n-silicon. The buried damaged layer, created by implanting Ar’ ions of energy 1.45 MeV and doses in the range 1013-1014 cm−2 at room temperature, is embedded within the depletion layer of a Schottky diode. The defects are characterized using capacitance-voltage (C-V), current-voltage (I-V) and deep level transient spectroscopy (DLTS). Large concentration of electrically active defects are found to occur in a region several microns beyond the ion range or the damage profile predicted by Monte Carlo simulations. The dominance of a single trap in the damaged region is established from hysteresis effect in C-V, space charge limited conduction in forward I-V characteristics and DLTS results. With annealing in the temperature range of 400-600C, the observed changes in defect charge profile indicate that the effective electrical interface moves progressively towards the surface. C-V characteristics have been simulated using model charge profiles which suggest presence of a compensated region and a sharp negatively charged defect profile at a distance much larger than that expected from ion range. Our results constitute experimental evidence of migration and clustering of interstitial related defects, even at room temperature in case of high dose irradiation.
Schottky Barrier Modification Of Low Energy Ar-Ion Bombarded GaAs And Si
Authors: Deenapanray P.N.K. , Auret F.D. , Goodman S.A. 
Published: April 2011

AbstractEpitaxially grown GaAs (p- and n-type) and n-Si were bombarded with low energy Ar-ions. Current voltage measurements on Schottky barrier diodes fabricated on the sputtered p-GaAs (Sc) and n-Si (Pd) showed that the series resistance and ideality factor were increased as the Arion dose was increased. The respective increase and decrease in barrier heights of Sc/p-GaAs and Pd/n-Si diodes were attributed to the presence of donor-type surface states in the bombarded material. The barrier heights of Au Schottky diodes made on n-GaAs changed nonmonotonically with Ar-ion sputter voltage. Variations of barrier height in the 0-1 kV range were explained by the introduction of donor-type defects. We demonstrated that the introduction of high concentrations of continuous level defects above 1 kV resulted in Fermi level pinning to become the dominant mechanism for controlling the effective barrier of current transport. Our results have shown that Schottky barrier properties could be changed by controlled amounts by varying the bombarding ion dose or sputter voltage.
Electrical Characterization of 1 keV He-, Ne-, and Ar-Ion Bombarded n-Si Using Deep Level Transient Spectroscopy
Authors: Deenapanray P.N.K. , Auret F.D. , Ridgway M.C. , Goodman S.A. , Myburg G. 
Published: April 2011

AbstractWe report on the electrical properties of defects introduced in epitaxially grown n-Si by 1 keV He-, Ne-, and Ar-ion bombardment. Epitaxial layers with different O contents were used in this study. We demonstrate using deep level transient spectroscopy that the low energy ions introduced a family of similarly structured defects (DI) with electronic levels at ∼0.20 eV below the conduction band. The introduction of this set of identical defects was not influenced by the presence of O. Ion bombardment of O-rich Si introduced another family of prominent traps (D2) with levels close to the middle of the band gap. Both sets of defects were thermally stable up to ∼400 °C, and their annealing was accompanied by the introduction of a family of secondary defects (D3). The “D3” defects had levels at ∼0.21 eV below the conduction band and were thermally stable at 650 °C. We have proposed that the “DI”, “D2”, and “D3” defects are higherorder vacancy clusters (larger than the divacancy) or complexes thereof.