bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetoresistance Measurements on Boron-Doped and Undoped Ni3Al Thin Films
Authors: Patterson Edward C. , Henry L. L. 
Published: April 2011

AbstractMagnetoresistance measurements were performed in magnetic fields up to 5 T, to examine the effects of boron doping on the electron transport properties of Ni3Al thin (500 Å, nominal, thickness) films. Both a doped (~200 ppm B) and undoped film were investigated. Four-probe magnetoresistance (magnetic field = 50 G and 5 T) measurements indicate that both samples undergo a phase transition in the 200 K – 300 K temperature range.
Growth Behaviour of Engineered Porous Thin Films – Measurement and Modeling
Authors: Vick D. , Smy T. , Dick B. , Kennedy S. , Brett M. J. 
Published: April 2011

AbstractRecent experimental work has demonstrated that unique high porosity thin films may be ob- tained in physical deposition systems by combining glancing angle deposition with in situ sub-strate motion control [1-7]. The microstructure of these films consists of isolated columns engineered into shapes such as helices, posts, or chevrons. Due to the isolated nature of the columns, the films present a unique opportunity to study fundamental thin film growth behaviour and, in particular, the influence of the self shadowing mechanism in three dimensions. Apart from this academic motivation, there is the need to characterize the physical constraints imposed on the engineering of these films. In particular, this study will have implications for the realization of isolated, periodically arranged nanostructures envisioned for certain applications. Preliminary results from an ongoing study of growth dynamics, morphology, porosity, and scaling behaviour, and the dependence of these features on deposition parameters are presented below.
Unique Features of the Crystallization Kinetics of FeCrBSi Thin Films Obtained by Laser Ablation Deposition
Authors: Sorescu M. , Grabias A. 
Published: April 2011

AbstractPulsed laser deposition was used to obtain a metallic glass in thin film form using a Fe77Cr2B16Si5 amorphous ribbon as a target. The as-deposited films were annealed under the same conditions as the parent ribbon samples in order to compare their crystallization behaviors. Transmission Mössbauer measurements were performed to determine the crystallization products formed due to annealing of the Fe77Cr2B16Si5 ribbon. Conversion electron Mössbauer spectroscopy was used to obtain structural and magnetic information from the thin films as well as from the surface layers of the ribbons. Our Mössbauer study showed that crystallization behavior of the FeCrBSi thin films differs from both the surface and bulk crystallization of the ribbon. Crystallization occurs at lower annealing temperature for the thin film than for the bulk ribbon. Annealed films also contain iron oxides which are not observed in the crystallized ribbons. A formation of a very thin, protective oxide film at the surface of the ribbon is taken into account to explain the differences in the crystallization behavior of the films and ribbons.
Molecular Dynamics Simulation of Confined Glass Forming Liquids
Authors: Varnikl Fathollah , Scheidlerl Peter , Baschnagel Jörg , Kob Walter , Binder Kurt 
Published: April 2011

AbstractTwo model studies are presented in order to elucidate the effect of confinement on glass forming fluids, attempting to study the effects of the interactions between the confining walls and the fluid particles. In the first model, short bead-spring chains (modelling a melt of flexible polymers) are put in between perfectly flat, structureless walls, on which repulsive potentials act. It is shown that chains near the walls move faster (in the direction parallel to the walls) than chains in the bulk. A significant decrease of the (mode-coupling) critical temperature with decreasing film thickness is found. In the second model, a binary Lennard-Jones liquid is confined in a thin film, whose surface has an amorphous structure similar to the liquid. Although, as expected, the static structural properties of the liquid are not affected by the confinement, relaxation times near the wall are much larger than in the bulk. Consequences for the interpretation of experiments are briefly discussed.
Local Environment of Surface-Polyelectrolyte-Bound DNA Oligomers
Authors: Jeon Sangmin , Bae Sung Chul , Zhao Jiang John , Granick Steve 
Published: April 2011

AbstractTwo-photon time-resolved fluorescence anisotropy methods were used to study the dynamical environment when fluorescent-labelled DNA oligomers (labelled with FAM, 6-fluorescein-6-carboxamido hexanoate) formed surface complexes with quaternized polyvinylpyridine (QPVP) cationic layers on a glass surface. We compared the anisotropy decay of DNA in bulk aqueous solution, DNA adsorbed onto QPVP, and QPVP-DNA-QPVP sandwich structures. When DNA was adsorbed onto QPVP, its anisotropy decay was dramatically retarded compared to the bulk, which means it had very slow rotational motion on the surface. Motions slowed down with increasing salt concentration up to a level of 0.1 M NaCl, but mobility began to increase at still higher salt concentration owing to detachment from the surface-immobilizing QPVP layers.
Electrokinetic Phenomena in Montmorillonite
Authors: Marry V. , Dufrêche J.-F. , Bernard O. , Turq P. 
Published: April 2011

AbstractClays present remarkable electrokinetic features since they exist from very dilute colloidal state to nanoporous materials, according to the ration water/clay. The case of low volume fraction Vwater/Vtot which corresponds to compact systems is examined. The ionic distributions havebeen evaluated from Poisson-Boltzmann like models and compared to discrete solvent simulations. Electroosmosis and conductance ha v ebeen calculated, in the framework of the Mean Spherical Approximation (MSA) introduced in the Fuoss-Onsager transport theory.
Structure Determination of Ba8CoRh6O21, a New Member of the 2H-Perovskite Related Oxides
Authors: zur Loye H.-C. , Smith M. D. , Stitzer K. E. , Abed A. El , Darriet J. 
Published: April 2011

ABSTRACTSingle crystals of Ba8CoRh6O21 were grown out of a potassium carbonate flux. The structure was solved by a general method using the superspace group approach. The superspace group employed was R3m(00γ)0s with a = 10.0431(1) Å, c1 = 2.5946(1) Å and c2 = 4.5405(1) Å, V = 226.60(1) Å3. Ba8CoRh6O21 represents the first example of an m = 5, n = 3 member of the A3n+3mA'nB3m+nO9m+6n family of 2H hexagonal perovskite related oxides and contains chains consisting of six consecutive RhO6 octahedra followed by one distorted CoO6 trigonal prism. These chains in turn are separated from each other by [Ba]∞ chains.
Study of Fluoride Ion Motions in PbSnF4 and BaSnF4 Compounds With Molecular Dynamics Simulation and Solid State NMR Techniques
Authors: Chaudhuri Santanu , Castiglione Michael , Wang Francis , Wilson Mark , Madden Paul A. , Grey Clare P. 
Published: April 2011

ABSTRACTA combined approach, using solid state NMR and Molecular Dynamics (MD) simulations, has been employed in this work to investigate fluoride-ion motion in the PbSnF4 family of anionic conductors, materials that contain double layers of Sn2+ and M2+ cations. 19F MAS NMR spectra of PbSnF4 and BaSnF4 show that the fluoride ions are mobile on the NMR timescale (10−4 s), even at room temperature. In the case of BaSnF4, two different groups of fluoride ions were observed, one group corresponding to fluorine atoms between the layers of Ba2+ cations, and the other set, corresponding to mobile fluoride ions undergoing exchange between sites in the Ba-Sn and Sn-Sn layers. The 119Sn NMR suggests a highly distorted Sn environment in these compounds, consistent with the presence of stereoactive Sn lone pairs. MD simulations, using the Polarizable Ion Model, have been carried out to probe the conduction mechanism. These simulations are able to reproduce elements of the structure such as the reduction in the occupancy of the fluorine ions between the Sn-Sn layers. Anisotropic conductivity, involving primarily motion in the M-Sn layers, is predicted, consistent with the NMR results. In the case of BaSnF4, no motion involving the fluoride ions in the Ba-Ba layers is observed on the simulation timescale (10−12 s) and a cyclic mechanism of fluoride-ion motion involving two types of fluoride ions in the Ba-Sn layers is proposed.
Modified Sol-Gel Synthesis of Vanadium Oxide Nanocomposites Containing Surfactant Ions, and Their Partial Removal
Authors: Dobley Arthur , Zavalij Peter Y. , Schulte Jürgen , Stanley M. 
Published: April 2011

ABSTRACTRecently, there has been much interest in creating new layered transition metal oxides. Vanadium oxides may be used as sorbents, catalysts, and cathodes in lithium batteries. The modified sol-gel technique allows for some control towards the final structure of the compound. Using this technique, a new layered vanadium oxide phosphate material, containing the surfactant dodecylphosphate, has been synthesized. The compound was analyzed using powder XRD, TGA, SEM, FTIR, TEM, and solid state NMR for both 51V and 31P. V2O3(PO4C12H25)3Na2−xKx(H2O)3.2 is the general formula of the layered product with an interlayer spacing of 36.6 Å The initial compound is composed of a vanadium oxide phosphate layer sandwiched between two hydrocarbon layers. The synthesis, composition, and structure of the initial compound will be discussed. Interestingly, when this compound is calcined to 400°C, the structure changes and is possibly hexagonal. Preliminary results are presented on this calcined material.
A Computational Study of the Translational Motion of Protons in Zeolite H-ZSM-5
Authors: Franke M.E. , Sierka M. , Sauer J. , Simon U. 
Published: April 2011

ABSTRACTThe potential energy profile for proton translational motions between two neighboring Alsites in zeolite H-ZSM-5 is calculated by a combined quantum mechanics-interatomic potential function approach. Thepotential energies of the six stable intermediate proton positions and the five transition structures along this path show an almost symmetrical trend reaching the maximum in the middle between these sites. Therefore, the maximum barrier will decrease with decreasing SiO2/Al2O3 ratio of thezeolite. For the SiO2/Al2O3 ratio examined (190) an activation energy of∼ 210 kJ/mol is calculated. This is much lower than the energy of deprotonation, about 1300 kJ/mol. The deprotonation energy of an Al-OH-Si bridge is obviously partially compensated by the proton affinity of the Si-O-Si bridges.
Synthesis of Tetramethylammonium Polyoxovanadates
Authors: Steunou Nathalie , Bouhedja Laure , Maquet Jocelyne , Livage Jacques 
Published: April 2011

ABSTRACTTetramethylammonium (TMA) polyoxovanadates have been precipitated from aqueous solutions aroundpH 7. Decavanadate clusters (TMA)4[H2V10O28]•4H2O are formed at room temperature whereas a layered (TMA)[V4O10] mixed valence compound is formed under hydrothermal conditions.51V NMR spectra recorded on the solution at different temperatures show that upon heating decavanadate clusters are progressively transformed into cyclic [V4O12]4−metavanadates. This suggests that the mixed valence polyoxovanadates are formed via the ring opening polymerization of metavanadate precursors.
Chemical delithiation, thermal transformations and electrochemical behaviour of iron- substituted lithium nickelate.
Authors: Lavela Pedro , Pérez-Vicente Carlos , Tirado José L. 
Published: April 2011

ABSTRACTChemical deintercalation in Fe-substituted lithium nickelate and its effects on the thermal stability and electrochemical behaviour are studied. A sample with Fe:Ni ratio of 1:9 was used as the starting material. Chemical deintercalation of the ceramic product was achieved by acid treatment with 0.6 M aqueous hydrochloric acid solutions at room temperature. The atomic Fe:Ni ratio remained unaffected while the Li:(Fe+Ni) ratio decreased significantly down to ca. 0.5 after acid treatment. Infrared spectroscopy was used to discard a proton exchange side reaction. The initial open circuit voltage (OCV) of non-aqueous electrolyte lithium cells using the chemically deintercalated solids was ca. 3.7 V, while 3.0 V were obtained with the pristine oxide. Heat treating the deintercalated solids lead to oxygen evolution at 230°C with the formation of spinel rock-salt structure solids at 600°C. The improved thermal stability as compared with iron-free lithium nickelate is an interesting factor for battery safety.
In Situ Probing and Atomistic Simulation of a-Si:H Plasma Deposition
Authors: Aydil Eray S. , Maroudas Dimitrios , Marra Denise C. , Kessels W. M. M. , Agarwal Sumit , Ramalingam Shyam , Sriraman Saravanapriyan , Van de Sanden M. C. M. , Takano Akihiro 
Published: April 2011

ABSTRACTHydrogenated amorphous silicon thin films deposited from SiH4 containing plasmas are used in solar cells and thin film transistors for flat panel displays. Understanding the fundamental microscopic surface processes that lead to Si deposition and H incorporation is important for controlling the film properties. An in situ method based on attenuated total internal reflection Fourier transform infrared (ATR-FTIR) spectroscopy was developed and used to determine the surface coverage of silicon mono-, di-, and tri-hydrides as a function of deposition temperature and ion bombardment flux. Key reactions that take place on the surface during deposition are hypothesized based on the evolution of the surface hydride composition as a function of temperature and ion flux. In conjunction with the experiments, the growth of a-Si:H on H-terminated Si(001)-(2×1) surfaces was simulated through molecular dynamics. The simulation results were compared with experimental measurements to validate the simulations and to provide supporting evidence for radical-surface interaction mechanisms hypothesized based on the infrared spectroscopy data. Experimental measurements of the surface silicon hydride coverage and atomistic simulations are used synergistically to elucidate elementary processes occurring on the surface during a-Si:H deposition.
Amorphous Silicon and Silicon Germanium Alloy Solar Cells Deposited by VHF at High Rates
Authors: Yang Jeffrey , Yan Baojie , Smeets Jozef , Guha Subhendu 
Published: April 2011

ABSTRACTA modified very high frequency (MVHF) glow discharge technique is used to deposit amorphous silicon (a-Si) and amorphous silicon-germanium (a-SiGe) alloy solar cells at high deposition rates. High quality a-Si alloy solar cells have been obtained by using MVHF at deposition rates up to ∼10 Å/s. The cells show good initial and stabilized efficiencies comparable to those obtained from conventional radio-frequency (RF) glow discharge deposition at low rates (∼1 Å/s). However, high quality a-SiGe alloy solar cells are more difficult to achieve at high deposition rates. In this paper, we present the progress made on a-SiGe alloy solar cells by incorporating bandgap profiling and appropriate buffer layers. Using the improved a-SiGe alloy solar cells, a-Si/a-SiGe tandem configurations are made and results presented.
Carrier Transport in Ultra-Thin Nano/Polycrystalline Silicon Films and Nanowires
Authors: Kamiya Toshio , Tan Yong T. , Furuta Yoshikazu , Mizuta Hiroshi , Durrania Zahid A.K. , Ahmed Haroon 
Published: April 2011

ABSTRACTCarrier transport was investigated in two different types of ultra-thin silicon films, polycrystalline silicon (poly-Si) films with large grains > 20 nm in size and hydrogenated nanocrystalline silicon (nc-Si:H) films with grains 4 nm – 8 nm in size. It was found that there were local non-uniformities in grain boundary potential barriers in both types of films. Single-electron charging effects were observed in 30 nm × 30 nm nanowires fabricated in 30 nm-thick nc-Si:H films, where the electrons were confined in crystalline silicon grains encapsulated by amorphous silicon. In contrast, the poly-Si nanowires of similar dimensions showed thermionic emission over the grain boundary potential barriers formed by carrier trapping in grain boundary defects.
Nanocrystalline Silicon TFTs With 50 nm Thick Deposited Channel Layer, 10 cm2/Vs Electron Mobility and 108 On/Off Current Ratio
Authors: Min Robert B. , Wagner Sigurd 
Published: April 2011

ABSTRACTThin film transistors were made using 50 nm thick directly deposited nanocrystalline silicon channel layers. The transistors have coplanar top gate structure. The nanocrystalline silicon was deposited from discharges in silane, hydrogen and silicon tetrafluoride. The transistors combine a high electron field effect mobility of ∼ 10 cm2/Vs with a low “off” current of ∼ 10−14 A per µm of channel length, and an “on”/“off” current ratio of ∼ 108. This result shows that directly deposited silicon can combine high mobility with low “off” currents.
Identification of Growth Precursors In Hot Wire CVD of Amorphous Silicon Films
Authors: Duan H. L. , Zaharias G. A. , Bent Stacey F. 
Published: April 2011

ABSTRACTA soft ionization laser-based technique using 10.5 eV photon energy has been used to probe radical growth precursors in the hot wire chemical vapor deposition (HW-CVD) of a-Si:H. Using a Re filament, it is shown that Si, SiH3, and Si2H6are the major silicon-containing species formed from the hot wire dissociation of silane, and SiH2is at most a very minor product. However, chamber history is found to influence the radical species produced; i.e. SiH3 and Si2H6are largely related to the chamber wall and filament conditions. The gas species produced by W and Re filaments at wire temperatures between 1000oC and 2000oC have been studied and compared. Heating the filament to higher temperatures increases the flux of Si, SiH3 and Si2H6 in a similar fashion for both filament materials. Above 1800oC, the Si intensity saturates, while SiH3 and Si2H6show monotonic increase without saturation up to 2000oC.
Super Poly-Si And Transistor Formed by Nickel-Induced-Lateral-Crystallization
Authors: Cheng C.F. , Leung T.C. , Poon M.C. 
Published: April 2011

ABSTRACTNickel-Induced-Lateral-Crystallization (NILC) was carried out on a 6000 Å amorphous Si (a-Si) layer. 6000 Å NILC poly-Si was formed and the upper 5000 Å Si layer was then removed. When compared to the conventional 1000 Å NILC poly-Si, the bottom 1000 Å NILC poly-Si layer was found to have relatively larger grains, less grain boundaries and better transistor mobility. The new high quality (super) NILC poly-Si layer can potentially provide greater contributions for novel device and circuit applications.
Microstructure Characterization of Hydrogenated Amorphous Silicon Films by Rare Gas Effusion Studies
Authors: Beyer Wolfhard 
Published: April 2011

ABSTRACTThe effusion of the rare gases neon and helium, as well as of hydrogen, was studied for plasma deposited (boron-doped and undoped) hydrogenated amorphous silicon films, grown at various substrate temperatures. Rare gas atoms were incorporated into the material during the growth process or by ion implantation. The results suggest that helium and neon effusion spectra give information on the material microstructure.
Effects of Hydrogen Dilution on a-Si:H and its Solar Cells Studied by Raman and Photoluminescence Spectroscopy
Authors: Yue Guozhen , Owens Jessica M. , Weinberg-Wolf Jennifer , Han Daxing , Yang Jeffrey , Lord Kenneth , Yan Boajie , Guha Subhendu 
Published: April 2011

ABSTRACTa-Si:H films and their n-i-p solar cells were prepared using plasma-enhanced CVD. The samples were prepared with no-, low-, standard, and high-H dilution. Raman and photoluminescence (PL) were used to characterize the i-layer. The main results are (a) Raman shows typical a-Si:H mode except for a c-Si peak in the 450 nm-thick film with high-H dilution, and (b) PL shows two regimes. (I) Below the onset of microcrystallinity characterized by x-ray diffraction, a blue-shift of the 1.4 eV PL peak energy and a decrease of the band width occur. (II) Above the onset of microcrystallinity, the PL efficiency decreases by a factor of 4-5, and the PL peak energy is red-shifted toward 1.2 eV as the μc-Si volume fraction is increased. In addition, the solar cell open circuit voltage shows first an increase and then a decrease, correlating with the PL peak energy position. We conclude that the PL spectroscopy is a sensitive tool for characterizing the gradual amorphous-to-microcrystalline structural transition in thin film solar cells.
Control of Optical and Electrical Properties of ZnO Films for Photovoltaic Applications
Authors: Hunger Ralf , Iwata Kakuya , Fons Paul , Yamada Akimasa , Matsubara Koji , Niki Shigeru , Nakahara Ken , Takasu Hidemi 
Published: April 2011

ABSTRACTZnO films were grown by radical-source molecular beam epitaxy (RS-MBE) on sapphire and glass substrates, and they were characterized in terms of Hall mobility and optical transmission. Undoped ZnO films exhibit a low intrinsic defect density and optical properties close to bulk ZnO. By Ga doping, a resistance ρ as low as 2×10−4 Ωcm could be achieved. Balancing high conductivity and low transmission losses due to free carrier absorption in the infrared, the optimum was obtained for ρ=3.4×10−4Ωcm, electron mobility μe=37 cm2/Vs and an average transmission T of 96% in the wavelength range 400-1100 nm. Polycrystalline growth on glass yields slightly reduced but still good film quality (μe=30 cm2/Vs, T=90%). By the incorporation of Mg, conducting Mg0.3Zn0.7O films with an increased band gap up to ∼ 4eV were realized.
Structure Investigations of Several In-rich (Cu2Se)x(In2Se3)1−x Compositions: From Local Structure to Long Range Order
Authors: Chang C.-H. , Wei Su-Huai , Ahrenkiel S. P. , Johnson J. W. , Stanbery B.J. , Anderson T.J. , Zhang S.B , Al-Jassim M.M. , Bunker G. , Payzant E.A. , Duran R. 
Published: April 2011

ABSTRACTThe observed junction between α-CuInSe2 and the In-rich compositions in the β-phase domain (e.g. CuIn3Se5) appears to play an important role in the photovoltaic process [1]. There remain, however, inconsistencies and uncertainties about the boundary and structure of this phase. In general the structure of this phase belongs to defect tetrahedral family of structures [2], which can be described as normal tetrahedral structures with a certain fixed number of unoccupied structure sites. In this work, the local structures of various (Cu2Se)x(In2Se3)1−x semiconductor alloys in the β-phase domain were studied by Extended X-ray Absorption Fine Structure (EXAFS) and the results were compared to those for the α-CuInSe2 phase. The long- range order of these compositions was studied by X-Ray powder Diffraction (XRD) and electron diffraction. It was found the local structures of these compounds are well defined. These compounds, however, could not be well described by any long-range order structure model, especially the selenium position. First-principles band structure calculations were performed to assist in assigning crystal structures to CuInSe2, CuIn3Se5 and CuIn5Se8. The calculations indicated that the local environments of these compounds are well defined. Their long-range order might depend sensitively on growth history and the configurational entropies as suggested by the similar formation energies of several possible crystal structures for CuIn3Se5 and CuIn5Se8.