bluuebunny/crossref_metadata_2025 huggingface dataset:
Materials for a New Generation of Vehicles
Authors: Grobstein Toni
Published: April 2011

The Partnership for a New Generation of Vehicles (PNGV) is a national initiative with three goals: First, to significantly improve national competitiveness in manufacturing; second, to implement commercially viable innovations from ongoing research on conventional vehicles, and third, to develop a vehicle to achieve up to three times the fuel efficiency of today's comparable vehicle (ie, the 1994 Chrysler Concorde, Ford Taurus, and Chevrolet Lumina). Note this vehicle will have the equivalent customer purchase price of today's vehicles adjusted for economics, while meeting the customers' needs for quality, performance, and utility. Eight federal agencies are currently contributing to these goals, as well as the three principal US automobile manufacturers, numerous automotive component suppliers, research laboratories, and universities.

Materials research and development is a significant effort within PNGV. The goals in this area include development of lightweight, recyclable materials for structural applications, high strength, long-life, high temperature materials for engine components, improved materials for alternative propulsion and energy storage systems, and cost-effective process technologies and component fabrication methods. Application of advanced materials to automobiles will involve consideration of diverse factors, including weight savings, affordability, recyclability, crashworthiness, repairability, and manufacturability.
Improving the Electrochemical Performance of Carbon Filaments by Solvent Cleansing
Authors: Shui Xiaoping , Frysz Christine A. , Chung D. D. L.
Published: April 2011

Found inherent in the submicron-diameter vapor-grown carbon filament fabrication process was a tarry residue, which comprised polyaromatic hydrocarbons. Cyclic voltammetry conducted using carbon working electrodes and an iron cyanide electrolyte showed that the residue harmed the electrochemical performance. Removal of the residue from the filaments using a solvent resulted in increases in the electron transfer rate (to values as high as 0.2 cm/s) and reversibility of the iron cyanide redox species, increase in the packing density and decrease in the filament-filament contact electrical resistivity.
Pulsed Laser Deposition of Transition Metal Oxides for Secondary Batteries
Authors: Striebel Kathryn A. , Deng C. Z. , Cairns E. J.
Published: April 2011

Pulsed laser deposition has been used to prepare thin films of several complex metal oxides of significance in secondary batteries from a single stoichiometric target with a substrate temperature of 600°C in the presence of 200 mtorr O2. Films of the candidate bifunctional air electrocatalysts, for metal air batteries, Lao.6Cao.4CoO3, Lao.6Sr0.4CoO3, Lao.6Cao.4MnO3 and Lao.6Sro.4MnO3 were prepared on glassy carbon substrates. Glassy carbon was found to either erode during the ablation process (with the cobaltates) or cause film cracking after deposition because of its extremely low coefficient of thermal expansion.. The use of stainless steel substrates yielded 0.3μm-thick dense films of Lao.6Cao.4CoO3 and Lao.6Cao.4MnO3 which were suitable for electrochemical measurements in concentrated alkaline electrolytes. LiMn2O4 and LiCoO2 films were prepared at thickness' of 0.3μm and 1 5μm The 0.3μm-thick films delivered 176 mC/cm2-μm and 323 mC/cm2-μm for LiMn2O4 and LiCoO2, respectively, in 1M LiClO4/PC.
Search for Ion Induced Mixing in Ceramic-Ceramic Systems
Authors: Padmanabhan K.R.
Published: April 2011

Thin sputtered ceramic films deposited on ceramic substrates were subjected to either Kr+ or Xe+ ion bombardment for ion beam mixing studies in ceramic-ceramic systems. The amount of mixing if any was evaluated from Rutherford backscattering and Auger electron spectroscopy. In some instances ceramic films were deposited on epitaxial films or single crystal substrates for ion channeling analysis. No significant mixing was observed in any of the systems with ZrC. However, analysis of the interface in Si3N4/ SiC system indicates appreciable mixing and ion beam induced damage to the substrate. The mixing appears to be dose dependent for heavier ions.
Modification of the Structure-Phase State of Coatings by Ion Implantation Techniques
Authors: Korotaev A.D. , Tyumentsev A.N. , Pinzhin Yu.P. , Safarov A.F. , Bugaev S.P. , Shchanin P.M. , Koval N.N. , Vizir A.V.
Published: April 2011

Transmission electron microscopy was used to study the effect of nitrogen-ion irradiation on the microstructure of ion-plasma TiN coating deposited on a substrate of austenitic stainless steel. The principal peculiarities of the changes in the fine structure at the substrate-coating interface and in the bulk of the coatings having a thickness of several micrometers have been revealed for the conditions of ion-beam-assisted deposition and plasma-assisted deposition. Possible mechanisms for the effect of ion irradiation on the microstructure of the substrate-coating composition are discussed.
Effects of High Energy Ion Irradiation on Crystallization of Amorphous Germanium Films Deposited on Calcium Fluoride Substrates
Authors: Nakao Setsuo , Saitoh Kazuo , Ikeyama Masami , Niwa Hiroaki , Tanemura Seita , Miyagawa Yoshiko , Miyagawa Soji
Published: April 2011

Amorphous (a-) Ge films were deposited on air-cleaved CaF2 (111) substrates at different deposition temperatures (Td). The films were irradiated with 0.9 MeV Ge or Si ions at low ion current intensity (1c) l00nA/cm2. Their structural changes were studied by Rutherford backscattering spectrometry (RBS) -channeling technique and thin film x-ray diffraction (XRD) measurement. It was found that the films were epitaxially crystallized by Ge and Si ion irradiation although they included randomly oriented grains. Ge ion irradiation was more effective for the crystallization than Si ion irradiation. However, the amount of the randomly oriented grains was slightly higher when using Ge ions. On the other hand, ion irradiation to the films prepared at high Td also exhibited higher incidence of randomly oriented grains.
Molecular Dynamics Studies of the Ion Beam Induced Crystallization in Silicon
Authors: Marques L.A. , Caturla M.-J. , Huang H. , Díaz De La Rubia T.
Published: April 2011

We have studied the ion bombardment induced amorphous-to-crystal transition in silicon using molecular dynamics techniques. The growth of small crystal seeds embedded in the amorphous phase has been monitored for several temperatures in order to get information on the effect of the thermal temperature increase introduced by the incoming ion. The role of ion-induced defects on the growth has been also studied.
Study of Diamond Nucleation on Silicon Using Direct Negative Carbon Ion Beam Source
Authors: Ko Y.W. , Ahn Y.O. , Sohn M.H. , Park Y. , Kim S.I.
Published: April 2011

The initial nucleation stages of sp3 bonded amorphous diamond on silicon substrates have been investigated. The energy of the incident carbon ions/atoms is understood as a key parameter for the vapor phase formation of amorphous diamond like carbon coatings. SKION's solid state carbon ion source is used for this study. The ion source is UHV compatible and capable of producing a controlled energy ion beam in the energy range of 5-300 eV. In the initial stage of the deposition, carbon is found to be deposited as a silicon carbide up to a thickness of about 180Á at room temperature. Silicon is diffused to the surface and forms SiC. As the energy of the ion beam increases, the formation of silicon carbide becomes apparent. Further carbon ion bombardment then leads to the formation of an sp3 bonded amorphous diamond film. Post-annealing above 900°C leads to the formation of crystalline silicon resulting in a Si-rich SiC surface due to silicon out-diffusion.
Loss Measurements of Stoichiometric Ti and O Implanted LiNbO3 Waveguides
Authors: Williams E. K. , Ila D. , Sarkisov S. , Venkateswarlu P. , Poker D. B.
Published: April 2011

Planar waveguides created by the implantation at 500°C of 2.5 x 1017 Ti ions/cm2 and 7.5 x 1017 O ions/cm2 have been characterized for loss by the scattered light technique. Preliminary results indicate losses of less than 2.5 dB/cm.
A Molecular Dynamics Simulation Study of Defect Production in Vanadium
Authors: Morishita K. , Diaz De La Rubia T.
Published: April 2011

We performed molecular dynamics simulations to investigate the process of defect production in pure vanadium. The interaction of atoms was described by the EAM interatomic potential modified at short range to merge smoothly with the universal potential for description of the high energy recoils in cascades. The melting point of this EAM model of vanadium was found to be consistent with the experimental melting temperature. The threshold energies of displacement events in the model system are also consistent with experimental minimum threshold in vanadium, and its average was found to be 44 eV. We evaluated the efficiencies of defect production in the displacement events initiated by recoils with kinetic energy up to 5 keV, and found that the probability of cluster formation is smaller than that of simulated events in fee metals reported in the literature.
Optical Properties of Multi-Component Antimony-Silver Nanoclusters Formed in Silica by Sequential Ion Implantation
Authors: Zuhr R.A. , Magruder R.H. , Anderson T.S.
Published: April 2011

The linear and nonlinear optical properties of nanometer dimension metal colloids embedded in a dielectric depend explicitly on the electronic structure of the metal nanoclusters. The ability to control the electronic structure of the nanoclusters may make it possible to tailor the optical properties for enhanced performance. By sequential implantation of different metal ion species multi-component nanoclusters can be formed with significantly different optical properties than single element metal nanoclusters. We report the formation of multi-component Sb/Ag nanoclusters in silica by sequential implantation of Sb and Ag. Samples were implanted with relative ratios of Sb to Ag of 1:1 and 3:1. A second set of samples was made by single element implantations of Ag and Sb at the same energies and doses used to make the sequentially implanted samples. All samples were characterized using RBS and both linear and nonlinear optical measurements. The presence of both ions significantly modifies the optical properties of the composites compared to the single element nanocluster glass composites. In the sequentially implanted samples the optical density is lower, and the strong surface plasmon resonance absorption observed in the Ag implanted samples is not present. At the same time the nonlinear response of the these samples is larger than for the samples implanted with Sb alone, suggesting that the addition of Ag can increase the nonlinear response of the Sb particles formed. The results are consistent with the formation of multi-component Sb/Ag colloids.
Deposition of Cu Films for Laser Mirror by Partially Ionized Beam Deposition
Authors: Koh Seok-Keun , Yoon Young-Soo , Kim Ki-Hwan , Jang Hong-Gui , Jung Hyung-Jin
Published: April 2011

Partially ionized beam deposition of Cu thin films on glass at room temperature were carried out to fabricate Cu laser mirrors with good structural and reflectance properties. At a constant film thickness of 600 Å, the grain size of as-grown Cu films increased with acceleration voltage, and there was no indication of defects such as cracks and/or large pores in the film surface as shown in scanning electron microscopy images. Root-mean-square(Rms) surface roughnesses of the films with thicknesses of 600 Å were measured by atomic force microscopy. RmS surface roughness increased when acceleration voltage increased from 0 kV to 2 kV, but decreased at the acceleration voltage of 3 kV. RmS surface roughness of the film grown at 4 kV, however, increased again. At the acceleration voltage of 3 kV, reflectance of the films increased with the film thickness until 600 Å and decreased at the film thickness of 800 Å. The reflectance results showed that the Cu film deposited at 3 kV had higher reflectance than that of others. Our results suggest that it is possible to grow the Cu film with good structural and optical properties on glass substrate at room temperature by partially ionized beam deposition.
Formation of Buried Two-Dimensional Electron Gas in Gaas by Si Ion Doping Using Mbe-Fib Combined System
Authors: YANAGISAWA J. , Nakayama H. , Wakaya F. , Yuba Y. , Gamo K.
Published: April 2011

0.1 and 30 keV Si2+ focused ion beams (FIB) were implanted in two types of GaAs, one of which is semi-insulating (s.i.) GaAs, while the other is grown by molecular beam epitaxy (MBE). Successive regrowth over the implanted surface was performed using MBE-FIB combined system, and the resistance was measured. It was found that for 100 eV Si2+ FIB implantation, the sample was nonconductive without a post annealing at 800°C. After the post annealing, however, the sample became conductive, and the resistance was the same order in magnitude as the sample fabricated using 30 keV Si + FIB irradiation. This suggests a potential of selective formation of Si δ-like doped layers in GaAs and GaAs/AlGaAs using a low-energy FIB.
Pulsed Laser Deposition of Epitaxial Sr(RuxSn1-x)O3 Thin Film Electrodes and KNbO3/Sr(RuxSnl-x)O3 Bilayers
Authors: Christen H.-M. , Boatner L. A. , Englisht L. Q. , Géa L. A. , Marrero P. J. , Norton D. P.
Published: April 2011

Sr(RuxSnl-x)O3 is proposed as a new conducting oxide for use in epitaxial multilayer structures. The Sr(Ru0.48Sn0.52)O3 composition exhibits an excellent lattice match with (100)-oriented KTaO3, and films of this composition grown by pulsed laser deposition on KTaO3, SrTiO3, and LaAIO3 substrates have been analyzed by X-ray diffraction, Rutherford backscattering/ion channeling, and resistivity measurements. Epitaxial KNbO3/Sr(Ru0 48Sn0.52)O3 bilayers have been successfully grown.
Green Light Generated by Frequency-Doubling in LiNbO3 and LiTaO3 Thin Films
Authors: Kingston J. J. , Armani-Leplingard F. , Fork D. K. , Anderson G. B.
Published: April 2011

Thin films of LiNbO3 and LiTaO3 are grown by off-axis magnetron sputtering on A12O3 and LiTaO3 substrates. When stoichiometry is precisely controlled, the films display excellent crystallographic and morphologic properties and have optical losses that are acceptable for frequency-doubling. LiNbO3/A12O3 samples have rocking curve widths as low as Δω = 76 arc sec and rms surface roughnesses less than 1 nm. Rocking curves performed with a resolution of 12 arc sec in 2θ indicate that there is very little tilt to the grains. Most of the width of the standard rocking curve is associated with variations in the interplanar spacing. The LiTaO3 films have similar characteristics. LiNbO3/LiTaO3 samples have rocking curve widths as low as Δω = 28 arc sec. Again, there is very little tilt misalignment to the grains, and the best samples have rms surface roughnesses less than 1 nm. The LiNbO3/LiTaO3 samples are typically 650 nm thick and many have optical losses less than 5 dB/cm. The LiNbO3/A12O3 samples, typically 250 nm thick, have losses of 5–7 dB/cm. The higher modal intensity at the surface of the thinner films increases surface scattering losses.

We have generated green light by frequency doubling in LiTaO3 and LiNbO3 thin-film planar waveguides. Phase matching was achieved by both modal dispersion and quasi-phase matching.
Sputtered and Reactively Grown Epitaxial GdAIO3Films as Buffer Layers for C-Oriented YBa2Cu3O7-δFilms on R-Sapphire
Authors: Senz S. , Sieber H. , Zakharov N. D. , Lorenz M. , Hochmuth H. , Hesse D.
Published: April 2011

Thin films of the orthorhombic perovskite GdAlO3were grown on R-plane sapphire single crystals. Two different film growth methods were used,viz.(i) a chemical reaction of a Gd-O plasma with the sapphire crystals, and (ii) the reactive radio frequency (r.f.) sputtering of a GdAlO3target. Subsequently, YBa2Cu3O7-δ(YBCO) films were deposited onto the GdAlO3buffer by pulsed laser deposition (PLD). The GdAlO3and YBCO films were investigated by Xray diffraction pole figure analysis and transmission electron microscopy (TEM), including highresolution transmission electron microscopy of cross sections. Independent of the deposition method the GdAlO3films grew according to the nearly equivalent orientation relationshipsThe GdAlO3grains are additionally tilted by angles up to ± 3° around the sapphire [11.1] axis. On top of these buffer layers the YBCO films grew with c-orientation and with an in-plane rotation of 45°. YBCO films of 200 nm thickness on GdAlO3buffer layers with a thickness of 10 to 20 nm showed a Tc> 87 K and a jc(77 K) > 3×106A/cm2.
Computer Simulation, Design, and Characterization of a Nozzle for More Effective Delivery of Oxidizing Gases
Authors: Kraisinger C. J. , Fusina D. M. , Schlom D. G.
Published: April 2011

For the in situ growth of cuprate superconductors and related oxides by vacuum deposition methods it is desired to achieve as high a flux of oxidizing species as possible at the growing surface and as little as possible elsewhere within the reaction chamber. The well known gas flow equations derived by Knudsen, Clausing, and others which apply to the molecular flow regime were implemented in a computer algorithm to simulate the gas flow upon a substrate from hypothetical nozzles of several different geometries. The optimal design for a particular MBE chamber and substrate size was determined and such a nozzle was fabricated and characterized. A dysprosium-coated quartz crystal monitor was used to determine the oxidant flux. The measured result matches predictions of the computer model within a factor of three. The computer algorithm was also used to model the spatial distribution of ozone gas through a nozzle of another reported geometry, where measurements of the resulting flux had been made. The shape of the calculated flux distribution agrees to within a few percent and the absolute values of flux reported agree within a factor of two.
C-Axis Oriented Lithium Niobate Films on (001) Magnesium Oxide by Pulsed Laser Deposition
Authors: Lacey J. L. , Schlom D. G.
Published: April 2011

For the first time, epitaxial c-axis oriented lithium niobate (LiNbO3) films were grown on MgO (001) substrates. This orientation is relevant to the monolithic integration of LiNbO3 with GaAs for waveguiding, frequency doubling, and other opto-electronic applications. The epitaxial orientation relationship is (001 ) LiNbO3 parallel to (001) MgO and [100] LiNbO3 parallel to [110] MgO. Four equivalent in-plane orientations were observed, such that the lithium or niobium atoms along the [100] axis of LiNbO3 are bonded to the oxygen atoms on diagonal comers of the MgO unit cell. These epitaxial films were prepared by off-axis pulsed laser deposition at substrate temperatures of 775–800 °C in a 15–50 mTorr mixture of 5% O3 in O2.
Surface Band Gaps and Superexchange Interaction in Transition Metal Oxides
Authors: Pothuizen J. J. M. , Cohen O. , Sawatzky G. A.
Published: April 2011

In this paper, we discuss the change in the band gap of charge transfer insulators for different surface terminations. We have calculated the Madelung potential of the unreconstructed (100) surfaces of the rocksalt structured TM-O compounds (TM = Mn, Fe, Co and Ni). We also considered possible step defects on a (100) surface. The presented results are calculated in both the purely ionic case (TM2+O2−) and in the strong ligand p - cation 4s, phybridization (TM1+O1−) case. In both cases the charge transfer gap, Δ, for the surface is reduced compared to the bulk value. As a consequence of this reduction there is a large increase of the surface superexchange interaction, Jsur, and a decrease of the band gap.
Preparation and Electrical Properties of (Zr, Sn)TiO4 Dielectric Thin Films by Laser Ablation
Authors: Nakagawara Osamu , Tabata Hitoshi , Toyota Yuji , Kobayashi Masato , Yoshino Yukio , Katayama Yuzo , Kawai Tomoji
Published: April 2011

(Zr, Sn)TiO4 is considered as a promising dielectric material for microwave devices owing to the temperature stability of capacitance and excellent microwave properties. Preferential (111)-oriented (ZrSn)TiO4 thin film was obtained by an ArF laser ablation. Properties of the crystallized film were as follows; the temperature coefficient of capacitance TCC was 17.6ppm/°C at 3MHz and the dielectric constant εr, 38 in the microwave range of 1GHz˜10GHz. It has turned out that the crystallization of this material is quite effective for improving dielectrical properties. Surface morphologies were observed by atomic force microscope(AFM). Grains grew on the crystallized film at 1 μm × 1 μm size.
Rem and Tem Studies of Thin Film Growth Dynamics on si Surfaces
Authors: Minoda Hiroki , Tanishiro Yasumasa , Yagi Katsumichi
Published: April 2011

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A study of surfactant-mediated epitaxy of Ge on Si(111) surfaces was carried out by in-situ transmission electron microscopy (TEM) and reflection electron microscopy (REM). Formation of 3D islands on the Si(111)-In surfaces was suppressed because of a change of critical nucleation size of the 3D islands. It was also found that formation of misfit dislocations at the interface between Si and Ge films was promoted by predeposition of In.
Observation of Vacancy Clustering in Si Crystals During in Situ Electron Irradiation in a High Voltage Electron Microscope
Authors: Fedina L. , Landuyt J. Van , Vanhellemont J. , Aseev A.
Published: April 2011

The formation of vacancy clusters in various Si crystals covered with SiO2 and Si3N4 films has been studied by means of high-voltage and high-resolution electron microscopy using electron beam energies of 1000 and 400 keV, respectively, and at temperatures between 20 and 250°C. Small vacancy clusters of about 2-5 nm in the form of Frank dislocation loops and stacking fault tetrahedra were observed by irradiating the thinnest areas (< 20 nm) of the investigated silicon specimens. Vacancy clustering seems to be more complicated in the thicker parts (> 20 nm) of irradiated crystals. We assume that in these areas vacancy clusters may be formed only in Si layers near the interfaces Si-SiO2 or Si-Si3N4 and they may interact with interstitials without full recombination of the defects. This leads to the appearance of a new form of interstitial clusters such as {111}-defects as well as the usual interstitial {113}-defects associated with vacancy clusters during prolonged irradiation in the HVEM.
In-situ Hrem Heating Experiments at Very High Temperatures
Authors: Kamino T. , Saka H.
Published: April 2011

A specimen-heating holder which allows an observation of reactions of more than one materials, in a controlled manner, at such a high temperature as 1723K has been developed. Facet-unfacet transformation and reconstruction of Au-deposited Si surfaces have been observed at very high temperatures at near-atomic resolution.
Initial Stage of Oxidation on Si(111)-7×7 Surface Investigated by Scanning Tunneling Microscope
Authors: Ha Jeong Sook , Park Kang-Ho , Park Seong-Ju , Lee El-Hang
Published: April 2011

The initial oxidation of Si(111)-7×7 surface has been investigated by taking the STM images of samples dosed with oxygen at room temperature and high temperatures between 500°C and 750 °C. In particular, different site selectivities between two oxygen-induced features, bright and dark sites, were observed and explained in terms of the difference in potential energy curves. In addition to such a strong site selectivity under low oxygen partial pressure (l×10-9 torr), heavy surface etching by oxygen was observed at higher O2 partial pressures and temperatures resulting in the high density of monolayer-deep etch marks on terraces.
An In-Situ Tem Study of the Dynamic Behavior of Domain Walls in a Free-Standing Lead Titanate Thin Film Under External Stress
Authors: Ren S. B. , Lu C. J. , Shen H. M. , Wang Y. N.
Published: April 2011

The evolution of domain structure with external stress in a free-standing PbTiO3 ferroelectric thin film of ˜100nm in thickness is observed by in-situ TEM technique. The thin film is composed of granular grains of ˜100nm in diameter, most of them appear to be single-domained whereas others are multi-domained showing domains of different sizes(5˜20nm). For some single-domained grains new domains appear during tension. For multi-domained grains, rearrangement of domain walls and coarsening of domains have been observed during tension. In many cases the domain walls disappear under high stress, i.e., a multi-domained grain changes into a single-domained grain. However, it is also observed that a large portion of single-domained grains appear not to respond to external stress. The dynamic behavior of domain walls in very thin ferroelectric thin films may help to understand the switching of these very thin films.
Stark Effects on Band Gap and Surface Phonons of Semiconductor Quantum Dots in Dielectric Hosts
Authors: Mu R. , Ueda A. , Tung Y -S. , Henderson D. O. , Zhu Jane G. , Budai John D. , White W. C.
Published: April 2011

We have investigated quantum-confined Stark effect (QCSE) on GaAs and CdSe nanocrystals and the electric field effect on surface phonons of GaAs nanocrystals isolated in sapphire substrates. For a strongly quantum-confined system, GaAs quantum dots illustrated no exciton energy shift. When the excitons are weakly confined in CdSe, a ∼ 2 meV red-shift was observed. On the other hand, the results of the electric field effect on surface phonon are dramatic both phonon oscilator strength and freqnency. As the strength of the electric field increases, the total intensity of the surface phonon decreases. At the same time, an additional peak was also observed at 277 cm-1, which is about 3 cm-1 above the center frequency of the surface phonon mode of GaAs nanocrystals embedded in a sapphire host.
Femtosecond Nonlinear Transmission Study of Free-Standing Porous Silicon Films
Authors: Klimov V. , Mcbranch D. , Karavanskii V.
Published: April 2011

Large photo-induced absorption signals were observed in free standing porous silicon films in the spectral range from 1.1 to 2.5 eV using a femtosecond pump and probe technique. The measured nonlinear signal has a very fast component with relaxation constants from 800 fs to tens of picoseconds superimposed on the slow-relaxing thermal background. The spectral structure and relaxation dynamics of the short-lived component of transient absorption show the presence of molecular-like Si complexes with well defined energy levels and spectrally uniform picosecond relaxation dynamics.
Effect of γ-Irradiation on Photoluminescence of Porous Silicon
Authors: Astrova E. V. , Emtsev V. V. , Lebedev A. A. , Poloskin D. S. , Remenyuk A. D. , Rud' Yu. V. , Vitman R. F.
Published: April 2011

Properties of Porous Silicon (PS) subjected to gamma irradiation in an air ambient and in vacuum have been studied. Gamma-irradiation was carried out in usual room atmosphere, and in evacuated tubes. The samples of porous silicon were investigated by means of photoluminescence (PL) and infrared (IR) absorption. For the samples irradiated under atmospheric conditions, the PL intensity increases by several times as the dose increases up to 1019photons/cm2 and after that point it starts to go down. For a dose of ˜9.1019photons/cm2 the PL intensity falls by a factor of ˜50. The position of the spectrum maximum does not change, but the half-width of the spectrum increases by 2 or 3 times. In the case of gamma-irradiation in vacuum the PL intensity gradually decreases with increasing dose. IR absorption measurements showed variations of the intensity of Si-H and Si-O bands with the irradiation dose. Enhancement of PL at lower doses has been explained by irradiation assisted oxidation of PS at atmospheric conditions and its degradation at higher doses by suppresion of the light-emitting centers.
Phase Transformation of Germanium Ultrafine Particles at High Temperature
Authors: Nozaki S. , Sato S. , Ono H. , Morisaki H. , Iwase M.
Published: April 2011

Germanium (Ge) films were deposited on substrates whose temperature was kept at room (Ge-RT) or liquid nitrogen temperature (Ge-LNT) by the cluster-beam evaporation technique. The Raman spectra of both films with a double peak suggest that the crystal structure is not the ordinary diamond but the tetragonal one. The critical temperature for the phase transformation from the tetragonal into the diamond structure is found much higher than that for the Ge nanostructures deposited by the gas-evaporation technique. The Ge-LNT sample exhibits photooxidation and photoluminescence (PL) when it is exposed to the UV light. Their PL and optical absorption characteristics are strongly influenced by a combination of the photo-oxidation and thermal annealing treatments.
Synthesis of Size-Classified Silicon Nanocrystals
Authors: Camata Renato P. , Atwater Harry A. , Vahala Kerry J. , Flagan Richard C.
Published: April 2011

We report the synthesis of size-classified silicon nanocrystals by applying differential mobility analysis to an originally polydisperse aerosol of ultrafine silicon crystallites. Using the described technique, the average nanocrystal size can be tuned by simply adjusting an electric field. Samples of uncoagulated silicon nanocrystals have been obtained and size control has been achieved within 15–20% in the 2–10 nm size regime.
Optical and Structural Characterization of Arsenide/ Phosphide Interfaces Formed by Flow Modulation Epitaxy
Authors: Emerson D. T. , Smart J. A. , Whittingham K. L. , Chumbes E. M. , Shealy J. R.
Published: April 2011

Bulk GaAsP, 20Å-500Å GaAsP/GaInP single quantum wells and 70 Å period GaAsP/GaInP superlattices were deposited on GaAs substrates by Flow Modulation Epitaxy. In these structures, the disordered GaInP is lattice matched while the GaAsP is in tension with the As mole fraction varying from 0.6 to 1. The structures were studied using asymmetric x-ray diffraction, 1K photoluminescence, Raman scattering, transmission electron microscopy and atomic force microscopy. Raman and x-ray diffraction are used to assess the structural quality of the superlattices, especially with regard to the presence/absence of superlattice x-ray satellites and disorder activated longitudinal acoustic phonons. A model including the effects of composition, strain, and confinement on longitudinal optic phonons is described and used to estimate the composition, using Raman scattering, in the thin, pseudomorphic GaAsP layers in the superlattices. Photoluminescence is used to assess the composition of the interfacial layers in the single quantum wells and to determine transition energies in the superlattices. In addition, analysis of the heterostructure luminescence, including prediction of the energy band alignment as calculated with the model solid theory corrected for strain, is found to suggest the presence of a type II band alignment in the heterostructures for some values of GaAsP composition. Finally, Raman scattering and x-ray diffraction are used to compare arsenide to phosphide interfaces in GaAs and InP-based heterostructures.
Determining Thin Film Density by Energy-Dispersive X-Ray Reflectivity: Application to a Spin-on-Glass Dielectric
Authors: Wallace W. E. , Wu W. L.
Published: April 2011

A novel method for determining thin film density by energy dispersive x-ray reflectivity is demonstrated for a polymer-derived spin-on-glass dielectric intended for microelectronics applications. The effects of sample misalignment limit the accuracy of x-ray reflectivity as typically practiced. These effects may be properly accounted for by measuring the critical angle for reflection at many different x-ray wavelengths simultaneously. From this measurement, thin film density can be ascertained with much improved accuracy. The results of the x-ray reflectivity measurement are compared to those derived from MeV ion scattering.
Dislocation Formation in Trench-Based Dynamic Random Access Memory (DRAM) Chips
Authors: Ho H. , Hammerl E. , Stengl R. , Benedict J.
Published: April 2011

This paper reports on our studies of dislocation formation in trench capacitor DRAM structures. Experimental results on process dependence and layout dependence of dislocation formation in cell layouts with minimum feature sizes from 0.5 μm to 0.25 μm are compared to two-dimensional stress simulations. It is shown that the nucleation and spatial distribution of dislocations can be explained by considering stress fields which are influenced by the overlay of deep trench and shallow trench isolation structures.
Determination of Bulk Mismatch Values in Heterostructures” by TEM/CBED
Authors: Armigliato A. , Balboni R. , Frabboni S.
Published: April 2011

Using isotropic elasticity theory it is possible to determine the bulk mismatch in thinned, cross-sectioned heterostructures, where a relaxation occurs along the thinning direction. This is accomplished by measuring, in the central disk of a single Convergent Beam Electron Diffraction (CBED) pattern, the position of the High Order Laue Zone lines, which are sensitive to lattice parameters along different crystallographic directions. The results obtained in both uniform and graded Sil-xGex/Si heterostructures are in good agreement with bulk values deduced from independent techniques.
Measurement of Young's Modulus and Poisson's Ratio of Free-Standing Ag/Cu Multilayered Thin Films
Authors: Huang Haibo , Spaepen Frans
Published: April 2011

Strain measurement by laser diffraction was used in tensile testing of free-standing Ag/Cu multilayered thin films with repeat lengths between 3 nm and 3 μm. The mean value, for all the films, of the Young modulus was 83.1± 1.2 GPa, and of the Poisson ratio was 0.377±0.015. No variation with bilayer repeat length, and hence no “supermodulus” effect, was observed.
Kinetic Studies of Nanoscale Crystallization in Electronic Materials
Authors: Hayzelden C. , Batstone J. L.
Published: April 2011

We report a kinetic analysis of low-temperature NiSi2-mediated crystallization of amorphous Si by in situ transmission electron microscopy. The initiation of crystallization by formation of crystalline Si on buried NiSi2 precipitates is shown to have an activation energy of 2.8±0.7eV. Crystallization of the amorphous Si via migrating precipitates of NiSi2 occurs with an activation energy of 2.0±0.2eV. The significance of these activation energies is discussed in terms of possible atomistic mechanisms of crystalline Si initiation and subsequent growth. Amorphous Si is reported to crystallize at temperatures as low as 450°C.
Light Scattering Measurement Of Surface Topography During Formation Of Titanium Silicide.
Authors: Lavoie C. , Cabral C. , Clevenger L. A. , Harper J. M. E. , Jordan-Sweet J. , Saenger K. L. , Doany. F.
Published: April 2011

The evolution of the surface topography during the phase transformations of titanium silicide has been studied using elastic light scattering at two different collection angles. The light scattering measurements were performed simultaneously with x-ray diffraction and resistance measurements for titanium films deposited on either Si(100) or on poly-silicon substrates. At selected points during annealing, the samples were cooled rapidly to room temperature and analyzed ex situ using Nomarski microscopy. We find that, depending on the detection geometry, the in situ light scattering shows preferentially the formation of the C49 or C54 TiSi2 phase as well as differentiates between inversion and agglomeration on poly-silicon substrates.
Nano-scale Imaging of Corrosion: Application of Scanning Polarization Force Microscopy
Authors: Dai Qing , Hu Jun , Freedman Andrew , Robinson Gary N. , Salmeron Miquel
Published: April 2011

Scanning Polarization Force Microscopy, a recently developed non-contact imaging technique, is employed for the study of sulfuric acid induced aluminum corrosion. The morphological changes occurring during the corrosion of aluminum by sulfuric acid droplets were imaged in situ with nanometer resolution using Scanning Polarization Force Microscopy. The results of these experiments not only demonstrate the potential applications of SPFM in imaging liquid surfaces and weakly adsorbed species, they also offer new insights into the mechanisms of atmospheric corrosion.
Effect of Heavy Doping on the Photoluminescence and Photoreflectance Spectra of Silicon and SiGe Layers.
Authors: Bru-Chevallier C. , Trui B. , Souifi A. , Brémond G. , Guillot G. , Chroboczek J. A.
Published: April 2011

PL and PR measurements have been performed on a set of silicon samples p-type doped between 1018 cm−3 and 1020 cm−3. Both optical methods are shown to be complementary as the bandgap narrowing effect is clearly evidenced from PL results, whereas low temperature PR results rather show the filling effect of the valence band, in good agreement with theoretical determinations. We observe an increase of E′0 transition as p-type doping level is increased.

PR spectra of Si and SiGe alloys at low temperature are presented together with theoretical fitting using the third derivative functional form of the unperturbed dielectric function of both direct optical transitions involved in the main PR feature : E′0 and E1.

This characterisation work will be discussed by pointing out that PL and PR results are closely connected, allowing the measurement of the effect of heavy doping on the Si and SiGe band structures.This study is fully relevant to high speed bipolar transistor development.
Monitoring Of Direct Reactions During Etching Of Silicon
Authors: Giapis K. P. , Minton T. K.
Published: April 2011

We present evidence of a direct reaction occurring when a hyperthermal fluorine atom beam (4.8 eV) impinges on a fluorinated silicon surface under steady-state etching conditions. When monitoring in-situ and in real time reactive scattering products by means of a quadrupole mass spectrometer, SiF3+ and SiF2+ are detected with bimodal time of flight distributions. The slow component can be described by a Maxwell-Boltzmann distribution at the surface temperature. However, the fast component is leaving the surface with velocities substantially higher than thermal and with a flux which does not obey the cosine law. Its translational energy increases with the angle of incidence of the hyperthermal fluorine beam. Etching in the direct reaction mode should result in highly anisotropic profiles by overcoming product desorption limitations.
Real-time Optical Monitoring of Epitaxial Growth Processes by p-Polarized Reflectance Spectroscopy
Authors: Dietz Nikolaus , Bachmannb Klaus J.
Published: April 2011

In this paper we introduce a real-time optical probe technique, p-polarized reflectance spectroscopy (PRS), for the monitoring of epitaxial growth processes. GaP heteroepitaxy by pulsed chemical beam epitaxy (PCBE) is used as an example. PRS allows to follow the deposition process with submonolayer resolution, utilizing a fine structure that is superimposed to the interference oscillations in the reflected intensity. This fine structure is explained by the periodic alteration of the surface reaction chemistry under pulsed chemical precursor supply. In the case of epitaxial GaP growth, it is modeled for a four layer stack, including an ultra-thin surface reaction layer of periodically changing thickness do(t) and dielectric function εo(t) tied to the periodic surface exposure to tertiarybutyl phosphine (TBP) and triethylgallium (TEG) pulses, respectively. The imaginary part of the dielectric function, εO2, of this surface reaction layer can be determined directly from the distance of the inflection points in the fine structure, where the optical response to the first precursor pulse in the cycle sequence changes sign, from the closests interference minimum. The surface reaction kinetics can be studied by analyzing the decay time characteristic in the transients of the fine structure.
Characterisation of the Oxidation Kinetics of Thin, Low Temperature, Electroless Plated Copper Films
Authors: Beechinor J. T. , O'Reilly M. , Patterson J. C. , Lynch S. , Lafferty E. , Kelly P. V. , Crean G. M.
Published: April 2011

The morphology, chemical state and oxidation behaviour of electroless copper films deposited from two different baths were characterised using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS) and spectroscopic ellipsometry (SE). The electroless solutions used were a commercial electroless formaldehyde (HCHO)-based solution (Cupro-Thick 84, Alfachimici) and an electroless solution developed within the NMRC which was based on dimethylamine borane (DMAB). Both methods produced as-deposited copper films with different morphologies. SE analysis of the as-deposited films and those oxidised in a dry synthetic air environment between 75°C–150°C indicated that the freshly deposited films had inherent oxide layers of between 45Å–92Å and that significant growth of these only occurred at temperatures above 100°C within 180 minutes isothermal oxidation periods. XRD analysis confirmed that the oxidation products formed were a mixture of cuprous oxide (Cu2O) and cupric oxide (CuO). Multiple linear regression analysis of the rates of change in oxide layer thicknesses as a function of both time and temperature indicated that mixed rate laws dominated. The application of an oxidation inhibitor was shown to prevent oxidation of the asdeposited commercial copper films when heat treated at 125°C.
Characterization of ZnSe:N Using Screening Effects
Authors: Kuskovsky I. , Neumark G. F.
Published: April 2011

Photoluminescence (PL) and Hall measurements allow one to obtain important parameters of semiconductors, such as impurity concentrations, compensation, and activation energies (EA). Usual analyses of such data assume constant EA. However, it is well known that EA depends on free carrier and impurity concentrations, and thus on temperature, due to screening effects. We here analyze literature data on ZnSe:N using screening effects. An observed decrease of EA with temperature (from PL data) had been used to suggest an interstitial site for N. With inclusion of screening, we obtained good agreement with the data, so that the idea of interstitial N is not required. In applying the screening theory to Hall measurements, we obtained lower impurity concentrations than with use of a constant EA. It is also to be noted that we fit both optical and electrical data with this approach. We further suggest that screening is the cause of an observed difference between optically observed and thermal activation energies.
Study of A+B-4C and A+2B–C Reaction-Diffusion System with Initially Separated Components
Authors: Yen Andrew , Kopelman Raoul
Published: April 2011

The presence of a reaction front is a characteristic feature of a variety of physical, chemical and biological processes. The reaction exhibits a front, provided that the diffusing reactants are separated in space. We study the reaction front dynamics of both A+B→C bimolecular and A+2B→C termolecular reactions with initially separated components in a capillary. We measure and compare with theory and simulations the dynamic quantities that characterize the kinetic behavior of the system: the global reaction rate R(t), the location of the reaction center xf(t), the front's width w(t), and the local production rate R(xft). The non-classical nature of this dynamical system is confirmed.
A Model for the Two-Phase Behavior of Fluids in Dilute Porous Media
Authors: Donley James P. , Nyquist Rebecca M. , Liu Andrea J.
Published: April 2011

Experiments show that the coexistence region of a vapor-liquid system or binary liquid mixture is dramatically narrowed when the fluid is confined in a dilute porous medium such as a silica aerogel. We propose a simple model of the gel as a periodic array of cylindrical strands, and study the phase behavior of an Ising system confined in this geometry. Our results suggest that the coexistence region should widen out at lower temperatures, and that the narrowness observed near the critical point may be a fluctuation-induced effect.
Quasi-Elastic Neutron Scattering Study of the Fragile Glass-Former Salol
Authors: Toulouse J. , Pick R. , Dreyfus C.
Published: April 2011

Quasi-elastic neutron scattering (NS) measurements of Salol have been carried out in order to study the α and β relaxations near the liquid-glass transition. The results are presented in the form of a susceptibility spectrum that is compared with the corresponding spectrum obtained from light scattering (LS) and with the predictions from the Mode Coupling Theory. The differences between the NS and LS results are due to the different correlators contributing to the susceptibility in the two types of scattering. The possible origin of these differences are discussed in the framework of the Mode Coupling Theory.
Interaction of Organic Additives with Alumina Surfaces in a Ceramic Slurry
Authors: Sigmund W. M. , Wegner G. , Aldinger F.
Published: April 2011

The interaction of organic additives with alumina surfaces was studied using a typical tape casting composition for alumina: solvent mixture trichloroethylene/ethanol, polyvinylbutyral (PVB) as binder and fish oil as dispersant.

The characterization of the single components revealed why the dispersant Menhaden fish oil has such excellent dispersing properties for colloids and slurries. Menhaden fish oil used for wet-chemical processing was found to be a chemically polydisperse polymer with a dispersity of D=45 (by GPC) and a molecular weight of Mw=28,000.

The investigation of the interaction in the highly concentrated colloidal slurry indicates that the high molecular weight fraction of fish oil is preferentially adsorbed and that an onion like supramolecular structure is formed by the ceramic particle/dispersant/binder system. The sequence in this nanostructure can be controlled by the sequence of addition of the compounds and is guided by polymer effects. The results gained on powders are supported by experimental data from surface plasmon resonance spectroscopy (SPR).
Saxs Characterization of Pyrolytic Carbon Blacks
Authors: Sahouli B. , Blacher S. , Brouers F. , Sobry R. , van den Bossche G. , Darmstadt H. , Roy C.
Published: April 2011

The surface fractal dimension (Ds) of pyrolytic carbon blacks (CBp) was determined using small angle X-ray scattering (SAXS). The CBp were produced by vacuum pyrolysis of used tires at different temperatures and pressures. For the CBp a dependence of the pyrolysis conditions on the fractal dimension was observed. The fractal dimension decreases, suggesting a smother surface, with increasing pyrolysis pressure and to a lesser intent with increasing pyrolysis temperature. Earlier SIMS and ESCA investigations have indicated that an evident correlation exists between the surface morphology and the surface chemistry of the CBp. According to these investigations, the smoothing of the CBp surface is due to the formation of carbonaceous deposits from adsorbed hydrocarbons on the CBp.
Evolution of the Structure Factor in Gelling Dense Colloidal Silica
Authors: Muzny C. D. , Butler B. D. , Hanley H. J. M.
Published: April 2011

A solution of 30 % by mass, 7 nm diameter, colloidal silica spheres has been studied during gelation using small angle neutron scattering (SANS). A peak in the static structure factor appears early at a wavevector q ≈ 0.1 nm−1, and then grows in height and shifts to lower wavevectors as gelation proceeds. This is consistent with a cluster growth model in which this low-q peak in the structure factor indicates the presence of correlations between growing clusters. The peak continues to grow after the solution has visibly gelled indicating that the gel coarsens even after a stiff solid-like network has formed. The clear presence of cluster correlations at length scales only one order of magnitude larger than the particle size means that the usual fractal slope analyses are invalid in this system. We interpret the results by comparing the measured time evolution of the structure factor with computer simulations of Lennard-Jones particles quenched far below the critical line.