bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a Model of on-Board Pemfc Powered Locomotive with a Metal Hydride Cylinder
Authors: Hasegawa H. , Ohki Y.
Published: April 2011

This paper presents a phase-zero evaluation case of installing on-off-board hybrid powered Electric Motor Vehicle (EMV) in existing and new local line and reports development of a model fuel cell powered locomotive. EMV such as electric car and locomotive are a new conceptual EMV using hybrid power between off-board substation and on-board Regenerative Fuel Cell (RFC) power system with Metal Hydride (MH) stored hydrogen generated with water electrolyzer by off-board surplus power. In this study, it is estimated a possibility to close power gap over 30 % in placing the new conceptual vehicle. The Locomotive is a 110 cm long locomotive powered by a 20 W PEMFC configured with 20 cells and supplied with about 2 g hydrogen, from a cylinder of 100 g metal hydride, and natural convection air (02). Measuring 50 cm (W), 50 cm (H), and weighting 25.9 kgf, the locomotive has a permanent magnet motor with a rated power 38 W (12 V, 3 A) and ran on railway that has a gauge of 126 mm (3'6“/8.5=4.94”), a length of 100 m. The performance of this train was acceleration of 0.5 m/s, cruising speed of 4.1 m/s at traction force of 15.8 N (1.6 kgf), average rolling friction of 5 N (460 gf).
Evaluation of the Humidification Requirements of New Proton Exchange Membranes for Fuel Cells
Authors: Grot Stephen A. , Hedstrom J.C. , Vanderborgh N.E.
Published: April 2011

Measurements of PEM fuel cell device performance were made with different gas inlet temperatures and relative humidity using a newly-designed test fixture. Significant improvement in device performance was observed when the fuel inlet temperature was increased above the operating temperature of the cell. These measurements were then correlated to a model to describe energy and mass transport processes.
Effects of the Electrolyte Composition on the Electrode Characteristics of Rechargeable Lithium Batteries
Authors: Morita Masayuki , Ishikawa Masashi , Matsuda Yoshiharu
Published: April 2011

A variety of organic solvent-based electrolytes have been studied for ambient temperature, rechargeable lithium (ion) batteries. The ionic behavior of the electrolyte system was investigated through conductivity measurements. The electrochemical characteristics of carbon-based materials (carbon fiber and graphite) as the negative electrode were examined in different compositions of the organic electrolytes. The electrolyte composition as well as the structure of the electrode material greatly influenced the charge/discharge profiles of the electrode.
Effect of CO2 on the Cycleability of Lithium Metal Anode
Authors: Momma Toshiyuki , Matsumoto Yasuhiro , Osaka Tetsuya
Published: April 2011

The lithium metal anode electrodeposited on nickel was studied by charge-discharge test coupled with in-situ ac impedance measurement. The test gives information about lithium anode interface and the modified interface of electrodeposited lithium by CO2 is confirmed to enhance the lithium cycleability. Also the CO2 protects the lithium interface in the presence of H20 impurity during cycling test.
Material Requirements for Lithium-Ion Batteries
Authors: Xie Like , Fouchard David , Megahed Sid
Published: April 2011

Lithium-ion (or ‘rocking-chair’) batteries with lithiated oxide cathodes and carbon anodes are finding increasing acceptance in many electronic applications including low rates (e.g., memory backup, real time clock, bridge function) and high rates (e.g., laptop computers, cellular phones, camcorders, etc.). This technology offers significant improvements in safety relative to cells using lithium metal anodes, with only a modest reduction in energy density. In general, materials for lithium-ion cells are chosen to minimize the energy density penalties associated with replacing the lithium electrode with an intercalation electrode. In this review paper, we describe the properties of the cathode, anode and electrolyte, and discuss requirements for improved materials for advanced lithium-ion systems. Consideration is given to energy density, rate capability, cycleability and thermal stability.
Carbon Surface Conditioning Produces an Anode Suitable for Heavy-Duty Discharge in Li Secondary Batteries
Authors: Takamura Tsutomu , Kikuchi Masahiro , Awano Hidekazu , Ura Tetsuya , Ikezawa Yasunari
Published: April 2011

Carbon fibers prepared at 1000 °C from mesophase pitch were treated with trimethyl silazane for modifying surface -OH group into trimethyl silyl group. The irreversible reduction current on the first cathodic sweep was diminished. Low-temperature carbon fibers prepared at 700°C and active carbon fibers were evaluated for electrochemical lithium doping and undoping reaction in propylenecarbonate(PC)/ethylene carbonate or PC/dimethyl carbonate mixtures(l:l) containing 1 M LiClO4 at room temperature.

Pristine samples prepared at 700 °C gave very poor reversibility and capacity on cyclic voltammograms(cv), but a constant current charge/discharge with a very low current gave a capacity over 400 mAh/g. After prolonged heating at 700°C, the cv characteristics were gradually improved. Partial oxidation in a mild oxidizing atmosphere at 700 °C for a few minutes was found to be quite effective in improving the cv characteristics remarkably. The charge/discharge capacity, however, was very similar to that obtained for the pristine sample at a very low consatant current. This indicates that the heat treatments effectively increase the electrochemical reaction rate of lithium doping and undoping, but have no effect on the intrinsic capacity.

Active carbon fibers were found to have considerable capacity after repeated oxidation/reduction cycles in solution. Partial oxidation treatment was also effective in increasing the charge/discharge current. The capacity after the treatment was over 400mAh/g, which is far larger than that of the double layer capacity of the sample.

The improvement due to the heat treatment is elucidated based on the removal of a surface inhibiting layer through the treatment.
Use of Submicron Carbon Filaments in Place of Carbon Black as a Porous Reduction Electrode in Lithium Batteries With a Catholyte Comprising Bromine Chloride in Thionyl Chloride
Authors: Frysz Christine A. , Shui Xiaoping , Chung D. D. L.
Published: April 2011

Submicron carbon filaments used in place of carbon black as porous reduction electrodes in carbon limited lithium batteries in plate and jellyroll configurations with the BCX (bromine chloride in thionyl chloride) catholyte gave a specific capacity (at 2 V cut-off) of up to 8700 mAh/g carbon, compared to a value of up to 2900 mAh/g carbon for carbon black. The high specific capacity per g carbon (demonstrating superior carbon efficiency) for the filament electrode is partly due to the filaments' processability into sheets as thin as 0.2 mm with good porosity and without a binder, and partly due to the high catholyte absorptivity and high rate of catholyte absorption of the filament electrode.
Porous Nickel Oxide Films for Electrochemical Capacitors
Authors: Liu Kuo-Chuan , Anderson Marc A.
Published: April 2011

NiO/Ni composite thin films consisting of nano-sized particles have been found to perform as good electrodes in electrochemical capacitor applications. These films can provide a specific capacitance of 25-40 F/g. The low cost of raw materials and easy manufacturing process of this system should allow one to produce low-cost electrochemical capacitors.
Amorphous Thin Film Ruthenium Oxide as an Electrode Material for Electrochemical Capacitors
Authors: Jow T.R. , Zheng J.P.
Published: April 2011

Ruthenium oxide thin films of an amorphous phase were successfully prepared on a titanium (Ti) substrate at temperatures below 160 °C. The sol-gel process using metal alkoxide precursor in nonaqueous solvents was used to prepare these films. The preliminary results showed that a specific capacitance of 430 F/g can be achieved for amorphous ruthenium oxide electrode in sulfuric acid. Films prepared by this method are compared with the films prepared by the thermal decomposition of the aqueous ruthenium chloride solution at temperatures above 300 °C. The specific capacitance, the crystalline structure, and the surface morphology of these films as a function of the preparation temperature were also discussed.
A New Charge Storage Mechanism for Electrochemical Capacitors and Charge Storage Density Vs. Crystalline Structure of Metal Oxides
Authors: Zheng JP. , Jow T.R.
Published: April 2011

The hydrous ruthenium oxide (RuO2.xH2O) powders with different contents of H20 have been formed by a sol-gel process and have been annealed at different temperatures. It was found that the specific capacitance of RuO2.xH2O is strongly dependent on the crystalline structure. The specific capacitance of over 720 F/g was obtained in an amorphous RuO2.xH2O. This value is at least two times greater than ever reported of this type of material.The specific capacitance dropped rapidly as the amorphous phase transforms into the crystalline phase at high temperatures. In contrast to the crystalline phase the specific capacitance of an amorphous RuO2.xH2O was not dependent on the specific surface area. The charge storage mechanism in amorphous RuO2.xH2O is different from that in the crystalline RuO2. The current in the cyclic voltammetric curve of RuO2.xH2O is nearly constant and is symmetrical with the potential in a range of 1 volts. The resistivity of pellets made from these powders is in the order of 10−3 Ω-cm.
Dependence of Battery Performance of Spinel Li1+XMn2O4 on the Preparation Method
Authors: Yoshio Masaki , Xia Yongyao , Ikeda Kazutaka , Noguchi Hideyuki
Published: April 2011

The formation process of the spinel phase by the melt-impregnation method was extensively investigated by the pore volume distribution measurement. Two kinds of the spinel structure compounds Li1+xMn2O4 optimized in this method were examined as a 4V cathode in a lithium nonaqueous cell. The first one has an initial charge capacity of 135-147 mAh/g and an unstable rechargeability with the characteristic two-step process, and another one delivers a slightly lower capacity of 105-120 mAh/g and ideal rechargeability with the quasi-one step process. These compounds preserve a capacity of more than 110 mAh/g for the first 100 cycles. The capacity fading on cycling of the former spinel only occurs at the second charge plateau in the rage of x<0.4 in LixMn2O4, and is due to the unstable two-phase structure for lithium intercalation coexisting in this region. The excellent rechargeability for the later spinel results from a homogeneous reaction occurring over the entire intercalated region.
Sputter Roughening Instability on the Ge(001) Surface: Energy and Flux Dependence
Authors: Chason E. , Mayer T.M. , Kellerman B.K.
Published: April 2011

We have measured surface roughening kinetics during low energy Xe ion sputtering of Ge (001) surfaces. The results are interpreted in terms of an instability theory developed by Bradley and Harper [1]. Although the calculated magnitude of the roughening rate does not agree with the measured value, the variation of the rate with ion flux and energy is in agreement with the theory.
New Insight into Damage-Related Phenomena in Si Implanted Under Extreme Conditions
Authors: Holland O. W. , Nielsen Bent , Budai J. D.
Published: April 2011

New insight into damage formation in Si(100) during self-ion irradiation is gained from processing under extreme conditions. Dislocations form in the near-surface as a result of lattice relaxation in response to strain produced by precursor defects which are shown to be vacancy-type by positron analysis. A model to account for these defects and their distribution is presented. A novel technique is demonstrated which utilizes a subsequent implantation as a depth specific probe to manipulate the vacancy-type defects. Aspects of damage growth which emerge from the probe results are discussed.
Deposition of Lead-Silicate Glassy Thin Coatings by Rf Magnetron Sputtering: Correlation Between Deposition Parameters and Electrical and Structural Properties
Authors: Rigato V. , Maggioni G. , Boscarino D. , Della Mea G.
Published: April 2011

Thin films (100–400 nm) of lead silicate glass have been deposited by RF magnetron sputtering in Ar plasma at different discharge conditions. The interaction of the sputtered species with the gas atoms during the transport process through the discharge region and the kinetics of growth of the films have been investigated as a function of the target composition and of the substrate temperature. This study demonstrates the possibility of controlling the surface electrical resistance of the films in a wide range of values ranging from 1012 to 1017 during the film growth.
Ion Beam-Induced Changes in Optical Properties of MgO
Authors: Qian Ying , Ila D. , He K. X. , Curley M. , Poker D. B. , Boatner L. A.
Published: April 2011

The implantation of Ag into MgO (100) single crystals, followed by thermal annealing at 1100°C, leads to dramatic changes in their optical properties. The changes in the optical properties are due to the presence of small Ag clusters which are formed in the annealed samples. The small Ag clusters are obtained by thermal annealing of the implanted MgO crystals between 600°C and 1100°C to investigate the changes in cluster sizes and to correlate with changes in their optical properties. Sample characterization is carried out using optical spectrophotometry to confirm the effective presence of Ag clusters and Rutherford Backscattering Spectrometry (RBS) to study the profile of Ag clusters.
Ion-Beam-Assisted Deposition of Metal Nanocluster thin Films with Nonlinear Optical Properties
Authors: Cotell C. M. , Carosella C.A. , Flom S.R. , Schiestel S. , Haralampus N. , Barnett T. W. , Bartoli F.J.
Published: April 2011

Metal nanocluster thin films (∼200 nm thickness) consisting of noble metal (Au) clusters (5-30 nm) in an active metal oxide (Nb2O5) matrix were deposited by evaporation or ion beam assisted deposition (IBAD). In some cases the films were given a post-deposition anneal. The microstructure of the films was examined by plan view and cross sectional transmission electron microscopy (TEM). The size of the metal nanoclusters was found to depend upon the temperature of the post-deposition anneal as well as the conditions of ion bombardment. Ion bombardment was found to stabilize smaller size particles. The linear optical properties of the films, as measured by VIS/UV spectroscopy, show particle size-dependent surface plasmon resonance effects. The nonlinear optical (NLO) properties of the nanoclusters in oxidized niobium were probed experimentally using degenerate four wave mixing (DFWM) and nonlinear transmission (NLT). The DFWM measurements yielded signals that showed strong evidence of saturation and give large values of χ(3)xxxxl. NLT measurements demonstrated that the nonlinear absorption coefficient and, hence, Imχ(3)xxxx was negative. Time resolved DFWM measurements exhibited dynamics that decayed on a several picosecond time scale. The magnitude and the picosecond dynamics of the NLO response were compared to those observed in gold nanoclusters formed by ion implantation in other media. The advantages of the IBAD method for fabricating third order NLO films include the ability to deposit films of arbitrary active region thicknesses and, more importantly, high cluster densities.
Titanium Nitride Formation by Low Energy Ar Ion Bombardment and UV-Light Irradiation During Deposition
Authors: Gerlach J.W. , Wengenmair H. , Stritzker B. , Rauschenbach B.
Published: April 2011

Titanium nitride films were produced by a newly developed photon and ion beam assisted deposition system (PHIBAD system). With an electron beam evaporator titanium was deposited on silicon substrates in a controlled nitrogen environment. The growing δ-TiN films were bombarded with argon ions and illuminated with UV-light. The results demonstrate that the impurity content, the nitrogen to titanium ratio of the films, the microstructure and the crystal alignment are changed using UV-light irradiation during ion assisted deposition.
Deposition of Boron Nitride Coatings by Reactive Rf Magnetron Sputtering: Correlation Between Boron and Nitrogen Contents and the Flux of Energetic Ar+ Ions at the Substrate
Authors: Rigato V. , Spolaore M. , Della Mea G.
Published: April 2011

Thin films of BNxOy have been deposited by rf Reactive Magnetron Sputtering from a BN target in Ar+ plasma (1 Pa) at different substrate bias conditions. The possibility of obtaining dense and hard BN coatings at a target-to-substrate distance larger than the mean free path of the B and N atoms has been investigated.

In order to deduce the plasma potential and the ion density near the substrates, the discharge characteristics have been measured by means of an electrostatic probe of the Langmuir type properly coupled to the glow discharge for avoiding the rf interference. From the probe data both flux and energy of the Ar+ ions have been determined and correlated to the net contents of boron and nitrogen as measured by means of the N(d,p) and 11Β(p,α) nuclear reactions. The results of this study show that in the investigated experimental conditions the flux of energetic Ar+ ions at the substrates is insufficient for promoting the formation of cubic BN as confirmed by XRD, FT-IR and nanohardness measurements. The reported data agree with recent literature findings and support the need of monitoring both the bombarding rate and energy of the Ar ions in rf discharges if the c-BN deposition is to be attained in a reproducible manner.
Ion Beam Reactive Sputter-Deposition of Silicon and Zirconium Oxides.
Authors: Pringle S.D. , Valizadeh R. , Colligon J.S. , Faunce C.A. , Kheyrandish H.
Published: April 2011

Oxides of silicon and zirconium have been deposited onto silicon, carbon and aluminium substrates by reactive sputtering using a 1 keV argon ion beam and a controlled partial pressure of oxygen. Using RBS, film composition was determined for a given partial pressure of oxygen and different Si or Zr deposition rates. There is evidence of retained argon in the film which is primarily due to argon ions reflected from the sputtered target. Cross-sectional TEM was used to examine the film microstructure and morphology. Both silica films and sub-stoichiometric zirconia films were found to be amorphous,whereas stoichiometric zirconia films were found to be polycrystalline with grain sizes in the range 10-20nm. A model has been developed to predict the composition of deposited films.
Tem and X-Ray Investigation of Single Crystal-Like Zirconia Films Fabricated by Dual Ion Beam Deposition
Authors: Ressler Kevin G. , Sonnenberg Neville , Cima Michael J.
Published: April 2011

Single crystal-like yttria-stabilized zirconia (YSZ) thin films have been deposited on amorphous quartz, polycrystalline zirconia, single crystal Si, and Hastelloy substrates using dual ion beam deposition (IBAD). These films are highly crystallographically aligned both normal to and within the film plane. The films are deposited at low substrate temperatures (<200°C), and the film orientation is substrate independent. θ-2θ X-ray diffraction, X-ray rocking curves, X-ray pole figures and X-ray phi scans are used to evaluate the film structure. High resolution cross-sectional TEM is used to examine the evolution of crystallographic film alignment on an amorphous quartz substrate. The data suggest that the evolution of biaxial alignment is nucleation controlled under these conditions.
Hyperthinning of Silicon and Sio2 for Low Power Electronic Applications
Authors: Oakes D.B. , Gelb A. , Green B.D. , Pirri A.N. , Wolfson R.
Published: April 2011

Silicon-On-Insulator (SOI) and advanced device technologies require the ability to fabricate uniform thin films of silicon (< 50 nm) and silicon dioxide (< 5 nm). A technique for hyper-thinning silicon and silicon dioxide films to these dimensions is described. The method is based upon etching by a high flux beam of hyperthermal (2 to 14 eV translational energy) fluorine atoms generated using Physical Sciences’ FAST technology. The fluorine atom beam contains greater than 95% atoms and less than 0.1% ions. The low ion content of the beam allows damage-free processing of these films. At the available translational energies, the fluorine atom reaction probability with silicon is near unity. Hence, high rate etching can be achieved. Silicon films have been thinned at ambient temperature (20 C) to thicknesses less than 50 nm by this technique with etching rates up to 120 nm/min demonstrated. The hyperthinning is uniform and does not affect the surface finish. Analysis of the processed surface shows no evidence of contamination from the treatment. High rate etching of silicon dioxide films has also been shown. The reaction probability of hyperthermal fluorine atoms with SiO2 films is 0.25.
Synthesis of Thin Membranes in Si Technology by Carbon Ion Implantation
Authors: Serre C. , Pérez-rodríguez A. , Calvo-Barrio L. , Romano-RodríGuez A. , Morante J.R. , Esteve J. , Acero M.C. , Skorupa W. , Kögler R.
Published: April 2011

The use of high dose carbon ion implantation in Si for the production of ultrathin membranes is investigated. Carbon implantations with doses up to 1018 cm-8 and energies up to 300 keV, at room temperature and 500°C were used, followed by 10 hours annealing at 1150°C. Structural and chemical analysis has been performed (including TEM, XPS, Raman and IR spectroscopies), and the etch properties have been investigated for KOH and TMAH etchants. It is found that doses higher than 1017 cm-2 are needed to obtain efficient etch-stop layers in TMAH, independently of the annealing conditions, while in contrast with previous work, it was not possible to obtain satisfactory results using KOH. According to this, ultrathin crystalline membranes (below 500 nm thick) with average surface roughness as low as 4.8 nm, measured by AFM, were obtained, and the structural analysis revealed the formation of a highly stable buried layer of crystalline β-SiC precipitates aligned with the Si matrix. These results corroborate the ability of high dose C ion implantation to obtain buried layers usable for micomachining applications.
Diffusion, Precipitation, and Cavity-Wall Reactions of Ion-Implanted Gold in Silicon
Authors: Myers S.M. , Petersen G.A.
Published: April 2011

The diffusion of Au in Si and its binding to cavities and to precipitates of the equilibrium Au-Si phase were investigated in the temperature range 1023-1123 K using ion implantation and Rutherford backscattering spectrometry. The diffusivity-solubility product for interstitial Au was found to be about an order of magnitude greater than the extrapolation of previous, indirect determinations at higher temperatures. Chemisorption on cavity walls was shown to be more stable than Au-Si precipitation by 0.1-0.3 eV in the investigated temperature range, indicating that cavities are effective gettering centers for Au impurities.
Carbon Implantation in AlX Ga1−X As
Authors: Pearton S.J. , Abernathy C.R.
Published: April 2011

Maximum hole densities of 4×1018 cm-3 were produced in Al0.3Ga0.7As by C+Ga implantation and subsequent annealing at ∼800°C. The activation efficiency decreases with increasing AlAs mole fraction and the use of higher temperatures for the Ga co-implantation, due to a reduced vacancy concentration under these conditions. The C diffusivity is ≤2×10−13 cm2sec−1 at 950°C in implanted Al0.3Ga0.7As, demonstrating that C is a much more thermally stable acceptor than Be, Mg, or Zn.
Optical and Electrical Properties of Heavily Carbon-Doped Gaas Fabricated by High-Energy Ion-Implantation
Authors: Shima Takayuki , Makita Yunosuke , Kimura Shinji , Harada Kentaro , Iida Tsutomu , Kotani Masanori , Osawa Akihumi , Shibata Hajime , Obara Akira , Kudo Kazuhiro , Tanaka Kuniaki , Kobayashi Eiichi , Hoshino Yasushi
Published: April 2011

High-energy (400 keV) implantation of carbon (C) ions was made into LEC-GaAs substrates with C concentration ([C]) of 1019− 1022Cm−3. 2 K photoluminescence (PL) and Hall effect measurements indicated that activation rate of C in LEC GaAs is both optically and electrically extremely low even after furnace-annealing at 850 °C for 20 min. For [C] = 1×1022 cm−3, two novel strong emissions were obtained and PL measurements as a function of excitation power and sample temperature suggested that the two emissions one at 1.485 eV and the other at 1.305 eV should reflect the formation of a new alloy between GaAs and C. Dual implantation of C+ and Ga+ ions was carried out to improve the activation or substitution rate. We found that nearly 90% activation rate can be achieved for C dose of 2.2 × 1013 cm−2.
Ion Beam Assisted Quantum well Intermixing
Authors: Goldberg R. D. , Mitchell I. V. , Charbonneau S. , Poole P. , Koteles E. S. , Aers G. , Weatherly G.
Published: April 2011

Significant progress has been made in the past year in the use of high energy (MeV) ion irradiation to tune the bandgap and therefore emission wavelengths of single and multiple quantum well structures. These shifts are attributable to compositional mixing across the well and barrier layer interfaces, a process that is driven by the vacancy flux, released during the anneal stage, from radiation defects. We present data from a series of measurements in both GaAs- and InP-based QW structures to demonstrate the importance of the implantation parameters chosen (ion species, energy, flux, fluence and implant temperature). The dramatic difference in the response of these two systems with regard to the implant depth is believed to be associated with the very different diffusivities of the Gp III site vacancies. Prospects for implementing the irradiation approach as a spatially selective, planar process in integrated optoelectronic circuitry look very attractive and are illustrated for both passive and active components by reference to recent results from tuned wavelength lasers.
Suppression of Secondary Defects in Silicon by Carbon Implantation
Authors: Simpson Todd W. , Mitchell Ian V.
Published: April 2011

We have examined the role of co-implanted carbon in suppressing the formation of secondary defects in self-ion irradiated Si(100). Implantation of 540 keV energy Si ions to a fluence of 1015 cm-2 followed by a 900°C, 15 minute anneal leads to the growth of an extended defect band at the end-of-range. Range matched carbon co-implantation can be used to modify this defect development dramatically. While direct co-implantation of carbon and silicon ions has no apparent effect on the formation of extended defects, such formation can be suppressed when the implanted C is incorporated substitutionally into the silicon lattice. Ion channelling and nuclear reaction analysis show that substitutional carbon is removed from substitutional sites during Si ion irradiation. In this case, it is proposed that excess interstitial silicon ions which normally lead to the growth of secondary defects will occupy the lattice sites previously occupied by carbon ions.
Structural and Magnetic Properties of Ion Beam Deposited Ag(1−x)Fex Films
Authors: Khan H.R. , Loebich O.
Published: April 2011

Nanocrystalline granular films of compositions Ag75Fe25, Ag61iFe39 are deposited on Si (001) substrates by ion beam deposition technique. The structure of as deposited and annealed (400°C/0.3 h) films is investigated by X-ray diffraction and the lattice parameter of the Ag particles is determined. The size of the Ag-particles is estimated from the line broadening of Ag(111) reflection and Scherrer formula and the values are 9 and 16 nm before and after the heat treatment. The magnetic moment and the saturation magnetization of the Fe-particles are determined from the magnetic field dependent magnetization data and using the Langevin function. A relationship between the structure and magnetism is discussed.
Structure Of Ceria Overlayer On Zirconia Crystal Studied by Surface Diffraction
Authors: Dmowski W. , Fu S. , Egami T. , Gorte R. , Vhos J.
Published: April 2011

We have utilized white x-ray beam and a Ge solid state detector, in energy dispersive mode, to study the diffraction from the surface layers of ceria deposited on (001) surface of Y stabilized cubic zirconia with grazing incident beam. We found that ceria forms islands, oriented epitaxially with respect to the zirconia substrate, with a lateral coherence of the order of 60 Å.
Properties Variation with Composition of Single-Crystal Pb(ZrxTi1−x,)O3 Thin Films Prepared by MOCVD
Authors: Foster C. M. , Bai G.-R. , Li Z. , Jammy R. , Wills L. A. , Hiskes R.
Published: April 2011

Single-crystal thin films covering the full compositional range of Pb(ZrxTi1−x)O3(PZT) 0≤x≤1 have been deposited by metal-organic chemical vapor deposition (MOCVD). The films were grown on epitaxial, RF-sputter-deposited SrRuO3 thin film electrodes on (001) SrTiO3 substrates. X-ray diffraction (XRD), energy-dispersive electron spectroscopy (EDS) and optical waveguiding were used to characterize the crystalline structure, composition, refractive index, and film thickness of the deposited films. We found that the PZT films were single-crystalline for all compositions exhibiting cube-on-cube epitaxy with the substrate with very high degrees of crystallinity and orientation. We report the systematic variations in the optical, dielectric, polarization, and transport properties as a function of composition and the epitaxy-induced modifications in the solid-solution phase diagram of this system. These films exhibited electronic properties which showed clear systematic variations with composition. High values of remnant polarization (30–55 μC/cm2) were observed at all ferroelectric compositions. Unlike previous studies, the dielectric constant exhibited a clear dependence on composition with values ranging from 225–650. The coercive fields decreased with increasing Zr concentration to a minimum of 20 kV/cm at the (70/30) composition. In addition, these films exhibited both high resistivity and dielectric-breakdown strength (˜1013 Ω-cm at 100 kV/cm and >300 kV/cm, respectively) without any compensative doping.
Optical Waveguides Using Epitaxial Bi4Ti3O12 Thin Films on MgO with CeO2 Cladding Layers
Authors: Jo William , Noh T. W. , Byun Y. T. , Kim S. H.
Published: April 2011

CeO2 thin films were grown on MgO(001) single-crystal substrates by pulsed laser deposition. The CeO2 thin films were used as a cladding layer of a Bi4Ti3O12 thin film waveguide. Structural properties of the BTO/CeO2/MgO heterostructures were investigated using x-ray diffraction techniques. An epitaxial relationship of BTO(001)//CeO2(001)// MgO(001) and BTO[100]//CeO2[100]//MgO[001] was confirmed. From the epitaxial heterostructure, a ridge waveguide was fabricated by photolithographic and ion-milling techniques. An single-mode near-field pattern was observed using an end-fire coupling method.
Structural, Electrical, and Optical Properties of Erbium-Doped Epitaxial BaTiO3 Films Grown by RF Sputtering
Authors: Barrios Pedro , Li Cheng Chung , Kim Hong Koo , Blachere Jean
Published: April 2011

We have investigated the epitaxial growth of Er-doped BaTiO3 films using rf magnetron sputtering. The Er-doped films (0.5 - 1 μm thick) were deposited on MgO (001) single-crystal substrates at various temperatures (500 - 800 °C). The films deposited at 700 °C or above arehighly (001)- oriented with an in-plane epitaxial relationship of BaTiO3[100] ║ MgO[100], as confirmed by X-ray diffraction. The Er doped films were found to be compressively stressed, as-deposited. The amount of stress monotonically decreases as a function of the deposition temperature. The Er-doped epitaxial films show a strong room-temperature photoluminescence at 1.54 μm, which corresponds to intra-transitions of Er3+ ions. Electrical characterizationswere carried out on Er-doped BaTiO3 films that were grown on MgO with a conducting In203 buffer electrode. The measurement shows that the Er-doped BaTiO3 films are ferroelectric with a remanent polarization of 1.5 μC/cm2 and a coercive field of 40 kV/cm.
Growth and Purity of Epitaxial Compounds
Authors: Flynn C. P. , Yang M.-H.
Published: April 2011

We report experience in our laboratory with the growth of epitaxial compounds using molecular beam epitaxy. These include the L12 structures, Laves phases, perovskite, bixbyite and spinels, with complicated structures and up to 80 atoms per cell. In many cases the growth takes place with surprising ease, even though the complexity of the process verges on self assembly. The paper describes diffusion measurements in epitaxial MgO directed towards the determination of impurity content and the level of structural defects. The synthesis of ‘ultrapure’ epitaxial MgO, and the resulting properties is described.
Modification of Epitaxial Oxide Films with Ion Implantation
Authors: Hong S. H. , Miller J. R. , Ma Q. Y. , Yang E. S. , Fenner D. B. , Yang C. Y. , Budnick J. I.
Published: April 2011

Ion implantation is used to modify the properties of oxide (YBCO and YSZ) thin films. Both superconducting and dielectric epitaxial oxide films, grown by laser ablation, are studied. The properties of the implanted oxide films are characterized by SIMS, XPS, DC resistivity and AC susceptibility measurements. By introducing reactive ions into superconducting oxide films, the conductivity of the material is inhibited possibly due to the interaction of the implanted ions with oxygen originally bound to the copper atoms. Al, Si, Ag and Ca ions are implanted into epitaxial YBCO films with injection energies ranging from 50 - 100 KeV and doses ranging from 1×1015 - 1×1016/cm2. XPS analysis shows that the implanted Si ions form SiOx. The inhibition method has been applied to the fabrication of superconducting electronic devices, such as SQUIDs. Dielectric oxide films are doped by the implantation of conductive and non-conductive ions. YSZ films are doped with Ag and Si ions and the ions are found to increase the conductivity.
Study of Grain Boundaries in YBCO Thin Films Using Microraman Spectroscopy
Authors: Martinez O. , Jimenez J. , Martin P. , Chambonnet D. , Degoy S. , Belouet C.
Published: April 2011

MicroRaman spectroscopy allows to identify the presence of c| and c⊥ oriented grains in YBCO thin films. This is achieved by the observation of two Raman modes associated with the oxygen sublattice vibrations, ˜500 cm−1 and ˜338 cm−1. The relative intensity of these Raman modes is related to the presence of c⊥ and c⊥;. oriented grains. Using the high lateral resolution of the Raman microprobe (<1 μm) some needle shaped grains of the films were scanned. The different Raman parameters were analyzed, showing noteworthy transformations at the [c|;]/[c⊥] boundaries. In particular the Raman mode corresponding to the out of phase O (2)– O(3) in plane vibrations (˜338 cm−1) was found to be narrowed, which should account for a decoupling of the phonon with the electronic continuum.
Large Area Uniform Deposition of YBa2Cu3O7 Thin Films by a 90° Off-axis Sputtering Technique
Authors: Rao R. A. , Gan Q. , Eom C. B.
Published: April 2011

Large area uniform deposition of Yba2Cu3O7 (YBCO) thin films on 8 inch diameter wafers, using a 3 inch diameter sputtering target and optimized substrate rotation in a single target 90° off-axis sputtering technique, is reported. The variation in thickness, composition and superconducting properties was studied as a function of substrate position on stationary and rotating substrates. The films deposited from a 3” target on rotating substrates displayed uniform thickness (< ±5% variation) and composition (< 2.3% deviation from target stoichiometry) and a consistently high transition temperature ( Tc > 88.3°K) over an 8” diameter area.
Epitaxy and Magnetotransport Properties of La0.8Sr0.2MnO3 Films Synthesized by Both Pulsed Laser Deposition and Novel Chemical Routes
Authors: Modak A. R. , Krishnan Kannan M.
Published: April 2011

La0.8Sr0.2 MnO3 thin films with different microstructural characteristics were prepared by both pulsed laser deposition and a novel polymeric sol-gel process. For both techniques, polycrystalline films were obtained on Si(100) with a native oxide surface but epitaxial and highly oriented growth could be induced on lattice-matched LaAlO3(100) substrates. Whilst the overall magnetization and magnetoresistance behavior as a function of temperature and applied field were consistent with recent results, i.e. a semiconductor-to-metal transition accompanied by an antiferromagnetic-to-ferromagnetic transformation and large magnetoresistance at the resistance peak temperature, the properties of the films were significantly different depending on the microstructure, epitaxy and polycrystallinity. Detailed microstructural characterization of the films are presented and correlated with their magnetic/magnetotransport properties.
Epitaxial Growth and Physical Properties of La1-xCaxMnO3-δ Thin Films on MgO(001) Substrates
Authors: Gu J. Y. , Kim K. H. , NOH T. W. , Lee Jeong Soo , Jeong Young Woo , Jo W.
Published: April 2011

Perovskite La1-xCaxMnO3-δ (LCMO) thin films with a wide range of x, i.e., 0.0 ≤ x ≤ 0.6, were deposited on MgO(001) substrates using a pulsed laser deposition (PLD) technique. Epitaxial La0.7Ca0.3MnO3-δ/MgO thin films were able to be grown under a condition such as 1.5 ∼ 2.1 J/cm2 of a laser fluence, 650 ∼ 750 °C of a substrate temperature, and 100 ∼ 300 mtorr of an oxygen pressure. X-ray pole figures and electron diffraction pattern showed that the LCMO films were grown epitaxially on MgO(001). Rutherford Backscattering Spectroscopy measurements investigated that the epitaxial LCMO films have compositions similar to those of targets, demonstrating the PLD is a useful technique to get films with complicated chemical compositions. Various physical properties, including resistance, R, magnetoresistance, ΔR/R(H=0) ≡ (R(H)-R(0))/R(O), and magnetization, M(T), were measured. The LCMO thin films with 0.2 ≤ x ≤ 0.5 had both semiconductor-metal and ferromagnetic ordering transitions, whose temperatures are located close to each other. These physical properties were explained in terms of the magnetic polaron model.
Filling Dependence of Magnetoresistance in Perovskite-type Manganese Oxide Films
Authors: Kasail Masahiro , Kuwaharal Hideki , Moritomol Yutaka , Tomioka Yasuhide , Tokura Yoshinori
Published: April 2011

Filling dependence of magnetotransport properties was investigated in Ndl−xSrxMnO3 films. Hysteretic behavior was observed in temperature dependencies of resistivity for restricted filling of x-0.35 and 0.50, indicating the occurrence of a first-order phase transition at low temperatures. The transition gives rise to a high-resistivity state which collapses to low-resistivity state under an external magnetic field. Change in resistivity by applying magnetic field was more than a order of magnitude. Origin of colossal magnetoresistance (CMR) is briefly discussed in terms of such a first-order phase change induced by a magnetic field.
Grain Boundaries of Controlled Geometry in ZnO Films Grown by Chemical Vapor Deposition: Undoped and Bi -Doped Boundaries
Authors: Majid I. , Liu Y. , Balluffi R. W. , Sande J. B. Vander
Published: April 2011

We describe a chemical vapour deposition technique for the controlled growth of ZnO films, containing grain boundaries which are suitable for detailed atomic resolution studies. Using this technique, we have grown; (1) random polycrystalline, (2) highly textured polycrystalline and (3) nominally single crystal films Also, a technique for doping the grain boundaries in these specimens with Bi by an “in-diffusion” method is demonstrated. The grain boundary atomic level structure and chemistry is studied by means of High Resolution Electron Microscopy (HREM) and STEM/EDX microanalysis. Some results obtained from boundaries in textured polycrystalline films which have the c-axes in neighboring grains lined-up to ˜1 ° are described.
A Study of Copper Oxide Films Fabricated by Pulsed Laser Deposition
Authors: Leuchtner R. E. , Hristakos L. S.
Published: April 2011

Copper oxide films were grown using the pulsed laser deposition (PLD) method with either a copper metal or a copper oxide target. A variety of deposition pressures of oxygen (0.001–0.3 torr) and temperatures (350, 450, and 550°C) were explored. From x-ray diffraction analysis, epitaxial <100> CuO films were observed at 450°C and either at 0.01 or 0.1 torr for the CuO and the Cu targets, respectively. Deposition rates were measured for the two targets (Cu and CuO) as a function of laser fluence and background gas pressure and enabled a morphological study of films prepared at different laser fluences but of similar film thickness (∼0.3 μm). The number density of particulates as well as the smoothness of the underlying film surface of the CuO films varied significantly with the target composition. The CuO films from the Cu target were the smoothest and had the fewest particulates.
In-Situ Observations of Electromigration-Induced Void Dynamics
Authors: Frankovic Richard , Bernstein Gary H.
Published: April 2011

Electromigration void nucleation and growth is a failure mechanism of integrated circuit (IC) metallization. The time-to-failure of interconnect lines depends on the void nucleation time and the void growth time. While much work has been done to model the void nucleation stage, the current understanding of the void growth stage is minimal. The importance of characterizing the void growth and motion dynamics is essential to further explain electromigration performance of IC metal interconnections.

Electromigration-induced voids previously studied have been observed to grow, coalesce, and even heal, but quantitative information on these dynamics is lacking. This work uses high-resolution electron-beam lithography to define sub-micrometer voids of various sizes and shapes into gold lines in order to observe void growth and movement with respect to initial void size and shape. The electromigration-induced dynamic behavior of pre-defined voids was measured in a field-emission scanning electron microscope in-situ. Results showed these prepatterned voids can re-fill or grow, and can yield quantitative results on dynamic void behavior.
In Situ Dynamic Atomic-Level Investigation of a Weak Charge Transfer Lamellar Intercalation Process
Authors: Diebolt L. , Sharma R. , Mckelvy M. , Glaunsinger W. S.
Published: April 2011

Environmental-cell dynamic high-resolution transmission electron microscopy (DHRTEM) has been used to provide atomic-level insight into lamellar reaction processes for the model weak- charge-transfer intercalation reaction of NH3with 2H-TaS2.In situintercalation was induced by exposing 2H-TaS2crystallites to controlled pressures of NH3(g) and recorded on videotape with 0.03 second time resolution. The intercalation processes observed possess a strong similarity to nucleation and growth processes. Onset occurs in either outermost or internal guest galleries, with further intercalation of the galleries progressing away from the onset layers. Randomly staged regions, containing occasional packages of short-range order, were observed to form during the growth process.
In Situ Real Time Observation of Chemical Vapor Deposition Using an Environmental Transmission Electron Microscope
Authors: Drucker Jeff , Sharma Renu , Weiss Karl , Ramakrishna B. L. , Kouvetakis John
Published: April 2011

Material synthesis by chemical vapor deposition (CVD) in a number of material systems has been investigated in real time using an environmental transmission electron microscope (ETEM) with 3.8 Å resolution. Here, we will focus on two metal / insulator systems. Al CVD onto SiO2from trimethyl amine alane and Au CVD from ethyl (trimethylphosphine) gold (I), also onto SiO2. For Al deposition, dendritic growth was observed for all pressure / substrate temperature combinations investigated for growth on untreated SiO2. Subsequent to reaction of the substrate surface with TiC14, almost immediate continuous Al film growth was observed. Growth rates for the Al film could be measured in situ by monitoring the evolution of the growth front at the Al/vacuum interface. In this system, very little enhancement in the metal film growth rate was observed as a consequence of electron beam irradiation for continuous films grown after TiCl4pretreatment.. This dramatically contrasts with the case of Au CVD investigated. In this instance, growth rate enhancements of up to 150 times were observed during electron beam irradiation as compared to purely pyrolytic decomposition of the precursor on the insulator surface. This growth rate enhancement decreased monotonically with substrate temperature. We surmise that this effect is related to the ratio of precursor surface residence time prior to ecomposition to the probability of collision from the impinging electron beam.
Fabrication of Novel III-N and III-V Modulator Structures by ECR Plasma Etching
Authors: Pearton S. J. , Abernathy C. R. , MacKenzie J. D. , Mileham J. R. , Shul R. J , Kilcoyne S. P. , Hagerott-Crawford M. , Ren F. , Hobson W. S. , Zavada J. M.
Published: April 2011

Quantum well microdisk laser structures have been fabricated in the GaN/InGaN, GaAs/AlGaAs and GaAs/InGaP systems using a combination of ECR dry etching (Cl2/CH4/H2/Ar, BC13/Ar or CH4/H2/Ar plasma chemistries respectively) and subsequent wet chemical etching of a buffer layer underlying the quantum wells. While wet etchants such as HF/H2O and HCI/HNO3/H2O are employed for AlGaAs and InGaP, respectively, a new KOH-based solution has been developed for AlN which is completely selective over both GaN and InGaN. Typical mask materials include PR or SiNx, while the high surface recombination velocity of exposed AlGaAs (∼105cm·sec-1) requires encapsulation with ECR-CVD SiNx to stabilize the optical properties of the modulators.
Siox Related Photoluminescence Excitation in Porous Silicon
Authors: Torchinskaya T. V. , Korsunskaya N. E. , Dzumaev B. R. , Sheinkman M. K.
Published: April 2011

Using PL, PLE, secondary ion mass spectroscopy (SIMS) and EPR investigations we show in this paper that two luminescence bands with different PL excitation spectra exist on the surface of silicon wires in PS.
Visible Luminescence from Surface-Oxidized Silicon Nanostructures: Three Region Model
Authors: Kanemitsu Yoshihiko
Published: April 2011

We discuss the mechanism of red luminescence from surface-oxidized Si nanostructures. The interface state between crystalline Si and SiO2 surface layer plays an essential role in efficient visible luminescence. The crystalline Si nanostructures with a disorder potential of interface states show complicated luminescence properties.
Possibility of Self-Trapped Excitons in Silicon Nanocrystallites
Authors: Allan G. , Delerue C. , Lannoo M.
Published: April 2011

We present semi-empirical tight-binding and ab-initio local density calculations demonstrating the (meta)stability of self-trapped excitons in silicon nanocrystallites. These are obtained not only for surface dimer bonds passivated for instance by hydrogen atoms or by silicon oxide but also for “normal” nearest-neighbors bonds. Light emission from these trapped excitons is predicted in the infrared or in the visible. We are thus led to the interpretation that part of the luminescence is due to such localized states while optical absorption is characteristic of quantum confinement effects. These conclusions should extend to other semiconductor crystallites.
Thermal Stability of GaAs/InGaP and InGaP/(In)GaAs Interfaces
Authors: Hyuga F. , Nittono T. , Watanabe K. , Furuta T.
Published: April 2011

Thermal stabilities of GaAs/InGaP and InGaP/(In)GaAs interfaces are investigated using InGaP/(In)GaAs/InGaP single quantum wells. Annealing is performed at a temperature range between 600 and 900 °C for 10 min. Positions and the full widths at half maximum (FWHM) of photoluminescence (PL) peaks are almost identical to those of as-grown ones up to 800 °C. Blue shifts of PL peaks and increased widths of their FWHM observed after 900 °C annealing are suppressed by shortening the annealing time to 0.1 sec. Annealing at 900 ‘C for 0.1 sec is sufficient to activate Si ions implanted into (In)GaAs layers. As a result, these thermal stabilities are able to provide high reliability and high performance of InGaP/(In)GaAs heterostructure MESFET ICs.