bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Evolution of NiTi and NiTiHf Thin Films
Authors: Zhang Chen , Zee Ralph H. , Thoma Paul E. 
Published: April 2011

AbstractThe microstructure evolution of Ti-rich NiTi thin films and (TiHf)-rich NiTiHf thin films containing 9at% Hf was investigated. These films were deposited from single NiTi and NiTiHf targets using a DC magnetron sputtering system. Free-standing films were obtained by using single crystal silicon substrates. The thickness of these films was controlled between 10-12 μm. In this investigation, the effects of deposition temperature on the surface and cross-sectional microstructures of these films were studied. Substrate temperature during deposition was varied between 300°C to 700°C at 100°C intervals. The influence of post deposition heat treatment (HT) temperature on the microstructure of these films was also studied. The post deposition HT temperature was varied between 300°C and 800°C at 100°C intervals. Both surface and cross- sectional microstructures were examined using a scanning electron microscope (SEM). The crystallinity and the phases present were determined using x-ray diffractometry. All the as- deposited films were found to be crystalline, even when the substrate temperature was as low as 300°C. Results from the microstructure analysis show that all the films have a relatively fine grain size ranging from 0.2 μm to 2.5 μm, and the grain size increases with increasing substrate deposition temperature. The effect of post deposition HT on grain size was found to be minimal.
The Early Oxynitridation Stages of Hydrogen-Terminated Single-Crystalline Silicon in N2O Ambient
Authors: Cerofolini G. F. , Camalleri M. , Condorelli G. G. , Fragalà I. L. , Galati C. , Lorenti S. , Renna L. , Viscuso O. 
Published: April 2011

AbstractOxynitridation of hydrogen-terminated silicon with N2O has been studied by x-ray photoemission spectroscopy. Our analysis has given evidence that the broad N(1s) peak at 398.3 eV usually reported in the literature is preceded by the formation of a very narrow peak at 397.3 eV, attributed to the moiety Si3N in which nitrogen is only marginally oxidized, and two other peaks (previously never reported) at 400.0 eV and 401.5 eV, attributed to the moieties Si2NOSi and SiNO, respectively.
A Study of Nucleation and Growth in MOCVD: The Growth of Thin Films of Alumina
Authors: Singh M.P. , Mukhopadhayay S. , Devi Anjana , Shivashankar S.A. 
Published: April 2011

AbstractWe have studied the nucleation and growth of alumina by metalorganic chemical vapor deposition (MOCVD). The deposition of alumina films was carried out on Si(100) in a horizontal, hot-wall, low pressure chemical vapor deposition (CVD) reactor, using aluminum acetylacetonate{Al(acac)3}as the CVD precursor. We have investigated growth of alumina films as a function of different CVD parameters such as substrate temperature and total reactor pressure during film growth. Films were characterized by optical microscopy, X-ray diffractometry (XRD), scanning electron microscopy (SEM), cross-sectional SEM, and secondary ion mass spectrometry (SIMS) compositional depth profiling. The chemical analysis reveals that the carbon is present throughout the depth of the films.
Modeling MOCVD Growth of YBCO Thin Films
Authors: Lo Tak Shing , Kohn Robert V. 
Published: April 2011

AbstractWe develop a new approach to the modeling of thin film growth. Our model treats the adatom density on the surface of the film as an explict unknown. This approach (1) clarifies the role of the “uphill current” associated with the Schwoebel barrier; (2) facilitates simple, physically natural coupling to the mechanism of deposition; and (3) permits discussion of multispecies effects. Our implementation focuses on spiral mode growth of YBCO thin films, with MOCVD (Metallorganic chemical vapor deposition) as the deposition mechanism.
Heteroepitaxial Growth Mode Transitions in the Presence of a Schwoebel Barrier at an Island Edge
Authors: Trofimov Vladimir I. , Mokerov Vladimir G. 
Published: April 2011

AbstractA recently developed model for homoepitaxial growth on a singular surface in the presence of a Schwoebel barrier at an island edge is extended to the case of heteroepitaxy (without lattice mismatch) by introducing different adatom mobilities in the first layer (heterodiffusion) and in all the next ones (self-diffusion).The model consists of an infinite set of rate equations for adatom and 2D island areal densities and coverage in successive layers. Growth behaviour depending on the model parameters is studied with emphasis on the transient growth regimes: layer-by-layer (LL) to a smooth multilayer (SML) and SML to a rough 3D growth. It is shown that a slower heterodiffusion relative to the self-diffusion leads to a smoother initial growth and thus retards the LL → SML growth trasition, whereas a faster heterodiffusion leads to a rougher initial growth and assists that transition and especially SML → 3D growth transitition at a higher Schwoebel barrier. It is found also that in a smooth growth regime nucleation kinetics eventually acquires a universal scaling form and the corresponding exponents are determined.
Structure of Charged Polymer Chains in Confined Geometry
Authors: Gilbert Elliot P. , Auvray Loïc , Lal Jyotsana 
Published: April 2011

AbstractThe intra- and interchain structure of sodium poly(styrenesulphonate) when free and when confined in contrast matched porous Vycor has been investigated by SANS. When confined, a peak is observed whose intensity increases with molecular weight and the 1/q scattering region is extended compared to the bulk. We infer that the chains are sufficiently extended, under the influence of confinement, to highlight the large scale disordered structure of Vycor. The asymptotic behavior of the observed interchain structure factor is ≍ 1/q2 and ≍ 1/q for free and confined chains respectively.
Dynamics of Sol-Gel Clusters and Branched Polymers
Authors: Zilman A. G. , Granek R. 
Published: April 2011

AbstractWe study the dynamics of sol-gel clusters. We find that the dynamic structure factor decays in time as a stretched exponential, and the viscoelastic modulus is an algebraic function of time. The difference beween screened and non-screened systems in the context of cluster dynamics is discussed.
Proton Spin-Relaxation Induced by Localized Spin-Dynamical Coupling in Proteins And in Other Imperfectly Packed Solids
Authors: Korb J.-P. , Van-Quynh A. , Bryant R. G. 
Published: April 2011

AbstractThe magnetic field dependence of 1H spin lattice relaxation rates in noncrystalline macromolecular solids including engineering polymers, proteins, and biological tissues is described by a power law, 1/T1 = Aω0-b, where ω0 is the Larmor frequency, A and b are constants. We show that the magnetic field dependence of the proton 1/T1 may be quantitatively related to structural fluctuations along the backbone that modulate proton-proton dipolar couplings. The parameters A and b are related to the dipolar coupling strength, the energy for the highest vibrational frequency in the polymer backbone, and the fractal dimensionality of the proton spatial distribution.
Mechanism for Ferromagnetic Resonance Line Width Broadening in Nickel-Zinc Ferrite
Authors: Hong Hee Bum , Byun Tae Young , Byeon Soon Cheon , Hong Kug Sun 
Published: April 2011

AbstractThe systematic variation in line width of ferromagnetic resonance with the Fe content was observed at X band (9.78GHz) in (Ni0.5Zn0.5)1−xFe2+xO4 (-0.2 ≤ x ≤ 0.2). The line width of the stoichiometric composition (x = 0) showed minimum value, 50 Oe. In contrast, the line width of the non-stoichiometric compositions sharply increased to 210 Oe with increasing nonstoichiometry (x). The mechanism for this line width broadening was investigated using thermoelectric power and electrical resistivity, since the contribution of anisotropy and porosity to the line width was negligible in this compositional region. In Fe excess region, Fe2+ ion concentration increased with increasing Fe content, resulting in line width broadening due to relaxation. But, it was suggested that Ni3+ and Fe2+ ions coexist in Fe deficient region. Therefore the increase of line width in nickel-zinc ferrites originated from the Fe2+ /Fe3+ magnetic relaxation in Fe excess region, and the Fe2+/Fe3+, Ni2+/Ni3+ magnetic relaxation in Fe deficient region.
Rock Wetting Condition Inferred from Dielectric Response
Authors: Araujo Yani Carolina , Araujo Mariela , Guzmán Hernán 
Published: April 2011

AbstractWettability is a manifestation of rock-fluid interactions associated with fluid distribution in porous media. Conventional wettability evaluation is performed by a sequence of spontaneous and forced displacements of different fluids into a porous sample, a method which is costly and time consuming. A new attractive approach is to estimate this quantity from dielectric measurements, since they can be done rapidly and economically.The dielectric frequency response of several rock samples of known wettability condition was studied in the range from 10 Hz to 100 MHz. Samples were saturated with brine and oil. The results confirm the strong influence of wetting condition on dielectric response. Water wet samples have significantly higher values of and (real and imaginary parts of generalized complex permitivity) than oil wet samples. In particular, the high frequency behavior of is most affected. Different regimes are identified as a function of frequency. They correspond to zones where different polarization effects are manifested. We quantify this effect and find a correlation with the modified Amott wettability index. Based on these findings, we propose an experimental protocol for the indirect measurement of wettability at laboratory scale.
Powder Diffraction Refinements of the Structure of Magnetite (Fe3O4) Below the Verwey Transition
Authors: Wright Jon P. , Attfield J. Paul , Radaelli Paolo G. 
Published: April 2011

ABSTRACTMagnetite is a classic example of a mixed-valent transition metal oxide, in which electronic conductivity and ferromagnetism result from electron hopping between octahedrally coordinated Fe2+ and Fe3+ states. Below the 122 K Verwey transition, the conductivity falls by a factor of ∼100 and a complex monoclinic (or triclinic) superstructure of the high temperature cubic spinel arrangement is adopted. This is assumed to be the result of Fe2+/Fe3+ charge ordering on the octahedral sites, but this has not been confirmed crystallographically, as single crystal refinements have been hampered by the extensive twinning that accompanies the Verwey transition. We have used very highly resolved powder diffraction data to attempt Rietveld refinements of the low temperature structure. The powder sample was prepared by grinding a single crystal of stoichiometric magnetite. Data were collected at 90 K on instruments HRPD at the ISIS neutron source, UK, and BM16 at the European Synchrotron Radiation Facility, France. The very high resolution of these data enables the monoclinic distortion to be observed, and the structure has been refined on the supercell proposed by Iizumi et al (Acta Cryst. B38, 2121 (1982)) with Pmca pseudosymmetry, giving parameters a = 5.94443(1), b = 5.92470(2), c = 16.77518(4) Å, β = 90.236(1)°. The mean octahedral site Fe-O distances differ from each other significantly, but the maximum difference between values is only 20% of that expected for ideal Fe2+/Fe3+ charge ordering.
Stability and Structural Characterization of Epitaxial NdNiO3 Films Grown by Pulsed Laser Deposition
Authors: Doan Trong-Duc , Abramowski Cobey , Salvador Paul A. 
Published: April 2011

ABSTRACTThin films of NdNiO3 were grown using pulsed laser deposition on single crystal substrates of [100]-oriented LaAlO3 and SrTiO3. X-ray diffraction and reflectivity, scanning electron microscopy, and atomic force microscopy were used to characterize the chemical, morphological and structural traits of the thin films. Single-phase epitaxial films are grown on LaAlO3 and SrTiO3 at 625°C in an oxygen pressure of 200 mTorr. At higher temperatures, the films partially decompose to Nd2NiO4 and NiO. The films are epitaxial with the (101) planes (orthorhombic Pnma notation) parallel to the substrate surface. Four in-plane orientational variants exist that correspond to the four 90° degenerate orientations of the film's [010] with respect to the in-plane substrate directions. Films are observed to be strained in accordance with the structural mismatch to the underlying substrate, and this leads, in the thinnest films on LaAlO3, to an apparent monoclinic distortion to the unit cell.
Quantum Critical Phenomena in the Ni S2−xSexSystem
Authors: Honig J.M. 
Published: April 2011

ABSTRACTElectrical conductivity experiments on NiS2−xSex(x = 0.45) subjected to moderate pressure in the 30 – 800 mK range permit the investigation of quantum critical phenomena in this system. Detailed data are presented in the context of standard theories of correlation effects in the vicinity of a critical point. The critical exponents pertaining to these effects have been evaluated; the significance of these findings require further study.
Bonding of Guest Molecules in the Tubes of Nanoporous Cetineite Crystals
Authors: Krasovskii E.E. , Tiedje O. , Brodersen S. , Schattke W. , Starrost F. , Jockel J. , Simon U. 
Published: April 2011

ABSTRACTA theoretical study of the optical excitation processes in cetineites is presented. This new exciting class of crystals with tubular structures displays photoconductivity, which strongly depends on the presence of guest molecules within the tubes. Based on self-consistent electronic structure calculations we present calculated dielectric function and photoelectron spectra of the (Na;Se) cetineite with the tube fllled with different guest molecules. Calculations are performed with the extended linear augmented plane wave kp method. The configuration and the arrangement of the filling molecules is derived from available crystallographic data and from heuristic arguments on chemical binding.
Theoretical Analyses of Spin Exchange Interactions in Extended Magnetic Solids Containing Several Unpaired Spins per Spin Site
Authors: Dai D. , Koo H.-J. , Whangbo M.-H. 
Published: April 2011

ABSTRACTFor extended magnetic solids containing several unpaired spins per spin site, we reviewed briefly recent progress in quantitative and qualitative methods of describing their spin exchange interactions on the basis of electronic structure calculations for their spin dimers.
Assembly of Metal-Anion Arrays within Dion-Jacobson-Type Perovskite Hosts
Authors: Kodenkandath Thomas A. , Viciu Marilena L. , Zhang Xiao , Sims Jessica A. , Gilbert Erin W. , Augrain François-Xavier , Chotard Jean-Noël , Caruntu Gabriel A. , Spinu Leonard , Zhou Weilie L. , Wiley John B. 
Published: April 2011

ABSTRACTThe construction of metal-anion arrays within Dion-Jacobson-type (DJ) perovskites was studied. A variety of hosts readily react with CuCl2 to produce compounds of the form (CuCl)[A'n-1(M,M')nO3n+1] (A' = alkaline earth, rare earth or Bi; M/M' = Nb, Ta, and/orTi; n = 2, 3). In contrast, CuBr2 only reacts with some of these hosts; this difference relative to the chloride may simply be a size effect. The formation of metal-anion arrays with other transition metals has also been examined. (FeCl)LaNb2O7 can be readily prepared from FeCl2, while reactions with FeBr2and NiCl2 under similar reaction conditions result in compounds of the formM0.5LaNb2O7 (M = Fe, Ni). The reductive intercalation of lithium and sodium into (CuCl)LaNb2O7 was also examined and was found to produce new compounds that have a large layer expansion.
A New Microporous Silicate With 12-Ring Channels
Authors: Plévert Jacques , Kubota Yoshihiro , Honda Takahisa , Okubo Tatsuya , Sugi Yoshihiro 
Published: April 2011

ABSTRACTA new molecular sieve GUS-1 is synthesized under hydrothermal conditions using a new organic compound acting as structure-directing agent. The structure determination reveals a framework with one-dimensional 12-membered ring channels running parallel. The structure exhibits the same channel net as zeolite ZSM-12 and shows the same projection of the framework along the pores as mordenite.
Preparation, Electrical Properties, and Water Adsorption Behavior of (1-x)Sb2O5·xM2O3·nH2O (M = Al, Bi, and Y; 0 ≤ x ≤ 1)
Authors: Ozawa Kiyoshi , Sakka Yoshio , Amano Muneyuki 
Published: April 2011

ABSTRACTBi, Y, and Al-doped antimonic acids with the empirical formula (1-x)Sb2O5·xM2O3·nH2O (M =Al, Bi and Y; 0 ≤ x ≤ 1) have been prepared by the direct reaction of an aqueous H2O2 solution with metal alkoxides. The electrical properties have been investigated by ac and dc conductivity measurements using a polycrystalline compactdisc as a sample, in connection with the water adsorption behavior. The (1-x)Sb2O5·xM2O3·nH2O (M = Bi and Y) materials exhibit a solid solution of cubic antimonic acid (Sb2O5·nH2O) with Bi2O3 and Y2O3 in the range of x = 0 – 0.1, and the ionic transference numbers of the materials are all over 0.98. The proton conductivity of (1-x)Sb2O5·xM2O3·nH2O (M = Bi and Y; x = 0.1) at room temperature increases to over 10-3 Scm-1 with an increase in the relative humidity. The conductivity is closely affected by the water adsorption behavior, which seems to be related to the introduction of oxygen vacancies.
A Composite Ionic-Electronic Conductor in the (Ca,Sr,Ba)-Bi Oxide System
Authors: Meen James K. , Gökçen Oya A. , Lin I-C. , Müller Karoline , Nguyen Binh 
Published: April 2011

ABSTRACTThe rhombohedral alkaline earth-bismuth oxide phase, an oxygen ion conductor, does not coexist stably with electronic conductors in any of the three binary systems, Ca-Bi-O, Sr-Bi-O, Ba-Bi-O. A thermodynamically stable composite of a rhombohedral phase that contains Ba and Sr or Ca or both with the electronic conductor BaBiO3 may be synthesized. The rhombohedral phase appears to have complete mutual miscibility of the alkaline earth elements. The composi- tions of rhombohedral phase that coexist with BaBiO3 in the Sr-Ba-Bi ternary system and the Ca- Sr-Ba-Bi quaternary systems are described. The value of ionic conductivity of the rhombohedral phase (at a constant Bi: [Ca+Sr+Ba]) is not dependent on the relative amounts of Ca, Sr, and Ba. The temperature at which the rhombohedral phase undergoes a polymorphic transformation from a low-temperature (2) form that is a weak ion conductor to a high-temperature (β1) form that is a much better oxygen ion conductor. The temperatures of the polymorphic transformation and of the upper stability limit of the rhombohedral phase both depend strongly on Ca: Sr: Ba. The β1 form develops in the Ba-Bi system at the lowest temperatures and at the highest ones in the Ca- Bi system. On the other hand, the Ca-Bi phase has greater thermal stability than its Ba ana- logues. The temperature range over which a useful composite conductor can operate is, there- fore, strongly dependent upon the bulk composition of the system.
Higher efficiency of n-i-p solar cells by Hot-Wire CVD at moderate temperatures
Authors: van Veen Marieke K. , Schropp Ruud E.I. 
Published: April 2011

ABSTRACTHot-Wire deposited amorphous silicon is an excellent material for the incorporation as the absorbing layer in n-i-p solar cells. We decreased the deposition temperature from 430 °C to 250 °C, keeping device quality (opto-)electrical properties of the a-Si:H layers. This enables application of Hot-Wire deposited a-Si:H in p-i-n structures and tandem solar cells. Layers deposited at 250 °C have been applied in efficient n-i-p and n-i-p/n-i-p solar cells. The deposition rate of the intrinsic layer was about 10 Å/s. No optical enhancements, like texturing or back reflectors, were used. Single-junction cells with a fill factor of 0.72 and an open-circuit voltage of 0.89 V have been produced. On a flexible stainless steel substrate, an initial efficiency of 7.2 % was recorded. Tandem cells also show a high fill factor (0.71) and open-circuit voltage (1.70 V), resulting in an initial efficiency of 8.5 %.
Light-induced Creation of Defects and Lifetime Distribution of Photoluminescence in a-Si:H Based Films
Authors: Ogihara Chisato , Takemura Hitoshi , Morigaki Kazuo 
Published: April 2011

ABSTRACTWe have studied the lifetime distributions of photoluminescence (PL) at 10K after the pulsed excitation for a-Si:H based films. Effects of light-induced creation of defects on the lifetime distributions have been studied. The lifetime distributions of PL in a-Si:H based films have a distinct component at about 10 ns together with a longer lifetime component seen in microsecond region. The PL in a-Si:H decreases in intensity after the illumination of visible light. The decreasing of the nanosecond component is slower than that of microsecond component. The decreasing of the PL intensity and increasing of the defect density have also been observed in a-Si:H after illumination of sub-bandgap light, although the absorption coecient is much smaller than that of visible light. The quenching of PL is discussed with distribution of non-radiative lifetime calculated by assuming random distribution of the DBs.
Femtosecond Carrier Dynamics in Nanocrystalline Silicon Films: The Effect of the Degree of Crystallinity
Authors: Myers K.E. , Wang Q. , Dexheimer S.L. 
Published: April 2011

ABSTRACTWe present studies of the ultrafast dynamics of photoexcited carriers in HWCVD nanocrystalline silicon thin films to address the underlying physics of carrier relaxation and recombination processes in this heterogeneous material. The degree of crystallinity is controlled by varying the H-dilution during deposition, yielding materials with increasingly larger grain size and crystalline fraction at higher dilution values. Time-resolved measurements of the carrier dynamics were made using a femtosecond pump-probe method, in which a short pump pulse excites carriers in the sample and a time-delayed probe pulse measures the resulting change in the optical properties as a function of the pump-probe delay time. Photoexcitation of carriers with pulses 35 fs in duration centered at 1.55 eV results in a net induced absorbance signal in the near-infrared that is analyzed in terms of a multi-component response that includes contributions from the silicon crystallites and the amorphous matrix.
Mechanisms of cross-talk in large area a-Si:H continuous image sensors
Authors: Mulato M. , Lu J. P. , Ready S. E. , Schuylenbergh K. Van , Ho J. , Lau R. , Boyce J. B. , Street R. A. 
Published: April 2011

ABSTRACTWe report studies of the image-blur effects caused by lateral cross-talk between neighboring pixels of large-area amorphous silicon (a-Si:H) image sensors. The lateral conduction is attributed to three effects: conduction along the interface between the a-Si:H film and the underlying passivation; field-dependent electron injection at the edge of the sensor; and a field enhancement of the interface conduction due to the bias applied to the address lines. We show that the cross-talk can be controlled by choice of the operating conditions and optimization of the materials.