bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solving Interface Structures by Combined Electron Microscopy and X-Ray Diffraction
Authors: Bourret A. , Feuillet G. 
Published: March 2011

AbstractBy a combination of high resolution imaging (HREM) and grazing incidence X-ray scattering (GIXS), periodic interfaces with large unit cell can be solved at an atomic scale. The advantage of recording information in the real space is that phases are directly encoded in the image. On the other hand the X-ray diffraction gives quantitative information at a resolution level better than with HREM. This combined analysis is illustrated on GaAs (001)-CdTe (111) and on GaAs(001)-GaSb(001) interfaces. In both cases the structure at the interface is obtained and some mechanisms for the strain relaxation at heterostructures with large misfit are proposed.
Quantitative Hrem Study of the Atomic Structure of the Σ(310)/[001] Symmetric Tilt Grain Boundary in Nb
Authors: King Wayne E. , Campbell Geoffrey H. 
Published: March 2011

AbstractWe have used a non-linear least squares optimization method to deduce a model for the atomic structure of the Σ(310)/[001] symmetric tilt grain boundary in Nb from high resolution electron micrographs (HREM) of a bicrystal prepared by diffusion bonding. The resultant model is similar to, but differs in detail from a theoretical prediction based on interatomic potentials which included angular forces thought to be important in the prediction of defect structures in body centered cubic metals. Results validate this approach as a step towards making HREM a quantitative technique.
Defect Relaxation in a-Si:H Studied by Defect Absorption and Luminescence
Authors: Han Daxing , Xiao Yang 
Published: March 2011

The experimental results about defect relaxation in a-Si:H have been reported recently on several transient measurements, such as forward-bias-transient-current,1 optical bias effect on electron drift,2 and photo-capacitance transient.3 In this paper we report the steady state results of the bias effect on sub-band-gap absorption and photon-emission spectra measurements in undoped samples.The optical bias effects the sub-band absorption. In additional to an enhancement of the sub-band gap absorption, the absorption threshold moved from 0.8 eV to 0.6 eV for undoped samples under optical bias at room temperature. The effects are larger in the light-soaked-state than in the annealed-state.We also report on the generation rate dependence on photoluminescence (PL) spectra line shape. We found that the energy position of the defect PL band shifted from 1.1 eV to 0.9 eV when the excitation level increased 4,000 times.While motion of the quasi-Fermi level as a explanation cannot be eliminated, defect relaxation seems more plausible.
Electronic Properties of a-SiNx:H Thin Film Diodes
Authors: Shannon J.M. , Sandoe J.N. , French I.D. , Annis A.D. 
Published: March 2011

Metal-semiconductor-metal diodes have been fabricated using a range of dilute a - SiNx:H alloys. Current transport in unstressed devices was dominated by thermionic-field emission of electrons through the reverse biassed metal-semiconductor contacts with a tunnelling effective mass ≈0.1me. The barriers to electrons were strongly pinned by bulk states and scaled almost linearly with optical band gap.Under high current stress, defect states were created below the Fermi level forming a -ve charge that changed the effective barrier height and produced drift in the current voltage characteristic. Unipolar stress measurements showed that this effect was related to hole transport. After prolonged stress the electrical characteristics were dominated by bulk effects due to the high density of metastable defects in the band gap.
Utility of the MÖssbauer Effect in the Assessment of Chemical Transformations in Unsupported Catalyst Systems as a Function of the Metal Salt
Authors: Good Mary L. , Akbarnejad M. , Patil M. D. , Donner J. T. 
Published: March 2011

ABSTRACTThis paper is presented to illustrate the utility of Fe-57 Mössbauer spectroscopy in the physical and chemical characterization of metallic catalysts as a function of preparation and subsequent treatment. The particular example chosen for investigation is the Ru-Fe bimetallic salt system which has significant potential as an active Fischer-Tropsch catalyst. The interpretation of the resulting Mössbauer parameters provides information on the chemical state of the metals as a function of treatment and initial salt properties and allows certain deductions to be made about particle size and solid state properties.
MÖssbauer Study of Iron and Tin Exchanged into Victorian Brown Coal
Authors: Cashion J.D. , Clark P.E. , Cook P.S. , Larkins F.P. , Marshall M. 
Published: March 2011

ABSTRACTMössbauer effect measurements have been taken of iron and tin introduced into brown coal to act as catalysts for hydrogenation. Spectra taken with 119Sn show that after introduction from solution, the tin appears as SnO2. During subsequent hydrogenation in an autoclave, some of the SnO2 is converted to β-tin and SnS. Ion-exchanged iron is shown from 57Fe measurements to occupy at least one site not populated in the native coal. Line broadening in this site and the other two original sites indicate the existence of variations in the local environment.
Nmr Study of Sodium Ion Mobility in a Single Crystal of Na β”-Alumina and Water Effects in Polycrystalline Samples
Authors: Hayes Cecil E. , Ailion David C. 
Published: March 2011

ABSTRACTWe measured the temperature dependence of T1 in a Mg-stabilized single crystal of Na β”-alumina. A comparison with earlier measurements on Li-stabilized polycrystalline samples indicates that, below 500K, the sodium ion kinetics are not directly affected by the stabilizing element. Above 500K our measured T1 shows a dependence on sample composition. Observations of NMR linewidth and signal intensity vs. water content indicate that, at low water concentration (< 2%), all sodium is in contact with water in its conduction plane; at higher water concentrations, the additional water may be forming complexes with some of the sodium.
Nuclear Magnetic Resonance in Alloys
Authors: Bennett L. H. 
Published: March 2011

ABSTRACTMany papers on NMR in alloys are addressed to NMR specialists rather than to metal or alloy specialists, and talk about the “potential” of NMR for application to alloys. This presentation emphasizes a review of some useful results of NMR experiments in alloys, including applications in diffusion, phase diagrams, magnetic materials, ordering in intermetallic compounds, liquid alloys and amorphous alloys.
Spin Susceptibility of Intercalated Graphite and Doped Polyacetylene
Authors: Kaufer James W. , Ikehata Seiichiro 
Published: March 2011

ABSTRACTWe have examined the electronic susceptibility of intercalated graphite and doped (CH)x using ESR [1]. The dopant in both cases was AsF5. For metallic intercalated graphite and for heavily doped (CH)x, the low frequency Schumacher-Slichter technique was used to determine the density of states at the Fermi energy. In the case of doped (CH)x, susceptibility measurements as a function of temperature allowed separate determination of the Curie and Pauli contributions.
Nuclear Magnetic Resonance Studies of Type II Superconductors
Authors: Fradin F. Y. 
Published: March 2011

ABSTRACTThe results of nuclear magnetic resonance (nmr) experiments on simple type–I superconductors were among the first and most important verifications of the BCS theory of superconductivity. In this paper, the application of nmr techniques to the study of superconducting properties in the more complex type–II superconductors will be reviewed. The discussion will include the effect of material parameters (e.g., degree of long range crystalline order, density of states at the Fermi level, effects of magnetic dopants) on the superconducting properties, including size of the superconducting gap, vortex structure, upper–critical field Hc2, and variations in Tc. Emphasis will be placed on high Tc, high Hc2 materials, i.e., A15 compounds and the ternary Chevrel phases.
The Anomalous Spectral Density Function for Diffusive Motion of Hydrogen in LaNi5H7
Authors: Chang H. , Lowe I. J. , Karlicek R. J. 
Published: March 2011

ABSTRACTMeasurements of T1 (Bo = 0.94T), and T1r as a function of temperature have been carried out on a LaNi5H7 sample at 4 different rotating magnetic field values. The T1 and T1r data are consistent with earlier data by Karlicek and Lowe [3,4], in which an asymmetry in the slopes of the log T1r vs. T−1 plot was found. The new data has been analyzed assuming a spectral density function J(ω,τc) of form J(ω, τc) = A(τc)B(Ω)F(ωτc), with τc = τc∞ exp(Ea/kT). This assumption leads to a spectral density function that fits all our data well, with Ea = 39 KJ/gm-Atom H, and J(ω)∼ Wω−1.35 in the high frequency limit. This Ea agrees well with the Ea obtained from diffusion constant measurements.
Nmr in Liquid Semiconducting Sex Te1-x
Authors: Dupree R. , Kirby D.J. , Gardner J.A. 
Published: March 2011

ABSTRACTFor x > 0.2, liquid SexTel-x alloys are semiconducting near the liquidus and have strongly temperature–dependent magnetic susceptibilities. We have studied the electronic paramagnetic centers by measuring their influence on the nuclear magnetic resonance shift and relaxation times of 77 Se and 125 Te in liquid Se .5Te.5. We find that the electronic centers are highly localized, their average hyperfine contact interaction with 125Te is three times that with 77Se, and the electronic spin correlation time is of order 1 psec at 350°C and decreases with rising T.
Muon Spin Depolarization in Metals with Dilute Magnetic Impurities
Authors: Brown J. A. , Heffner R. H. , Hutson R. L. , Kohn S. , Leon M. , Olsen C. E. , Schillaci M. E. , Dodds S. A. , Estle T. L. , Vanderwater D. A. , Richards P. M. , Mcmasters C. D. 
Published: March 2011

ABSTRACTMuon diffusion can be studied in metals without nuclear moments by the addition of paramagnetic impurities. We describe the theory and report measurements of muon depolarization in gold and silver doped with gadolinium and erbium. As well as diffusion rates, strength of the magnetic interaction and spin lattice relaxation rate of the paramagnetic ion are inferred from the data.
Dislocation Motion in Metals Investigated by Means of Pulsed Nuclear Magnetic Resonance
Authors: Tamler H. , HackelÖer H. J. , Kanert O. , Alsem W. H. M. , Th. J. , de Hosson M. 
Published: March 2011

ABSTRACTWe report the first use of nuclear magnetic resonance to investigate dislocation motion in metals. The spin-lattice relaxation rate in the rotating frame T 1ρ−1, of 27Al in polycrystalline, ultrapure Aluminium foils has been measured as a function of plastic-deformation rate έ for two different temperatures (77K and 300K). For έ = 0, the relaxation rate is determined by conduction electrons. For a finite deformation rate έ, an additional contribution to the relaxation rate arising from fluctuations in the nuclear quadrupole interaction due to dislocation motion is observed. From the motion-induced part of the relaxation rate the mean jump distance of a mobile dislocation is calculated which is determined by the density of lattice defects acting as obstacles for moving dislocations.
Geometrical Structure of Lattice Defect-Impurity Configurations Determined by TDPAC
Authors: Deicher M. , Echt O. , Recknagel E. , Wichert Th. 
Published: March 2011

ABSTRACTThe perturbed angular correlation technique (TDPAC) was applied to determine the orientation of the electric field gradient tensor induced by lattice defects at the probe 1l1In. The experimental results obtained for self-interstitials, vacancies and defect clusters in Cu, Ag and Au are shown and their microscopic interpretation is discussed.
Investigation of Lattice Defects in Hcp Metals
Authors: Keitel R. , Engel W. , Hoth S. , Klinger W. , Seeböck R. , Witthuhn W. 
Published: March 2011

ABSTRACTWith the perturbed angular correlation and distribution methods we studied the trapping and annealing of lattice defects in the hcp metals Cd and Zn. The defects were produced (i) by proton irradiation, (ii) by quenching, and (iii) by heavy ions recoiling after a nuclear reaction As probe ions we used 111Cd (i,ii) and 67Ge,69 Ge,71 Ge,113 Sn, and116 Sn (iii). The In-impurities in Zn and Cd are trapping centers for vacancies. At low temperatures (100 to 200 K) simple defect configurations are observed. In the in–beam experiments a sharp annealing step due to detrapping of vacancy type defects is found.
Nuclear Magnetic Resonance on Rare-Earith Nuclei in Re-Fe2 Intermetallic Ccmpounds
Authors: Berthier Y. , Devine R.A.B. , Butera R.A. 
Published: March 2011

ABSTRACTNMR results in RE-Fe2 internmtallic compounds at low temperatures are reported. Using a spin-echo spectrometer in the U.H.F. range, hyperfine field parameters have been measured on 167Er, 163Dy, 169 Tn and 159Tb at 1.4K. These cctnpounds have high Curie temperatures and the magnetic moment of the rare-earth, gJμB<Jz> is nearly saturated. The value of the iron moment is also known from Mossbauer measurements and accurate data for the hyperfine field at the rare-earth site obtained from NM enables us to extract the internal field due to conduction electrons.
MÖssbauer Study of New Laves Phases Rfe2 Compounds (R = Pr, Nd, Yb)
Authors: Meyer C. , Hartmann-Boutron F. , Gros Y. 
Published: March 2011

ABSTRACTA summary of the magnetic properties of three Laves Phases compounds RFe2 (R = Pr, Nd, Yb) synthesized under high pressure is presented. Most of the results have been obtained by Mössbauer spectroscopy. Through the 57Fe resonance, the easy directions of magnetization between 4 and 300 K have been determined; the hyperfine field at Fe contains a large anisotropic contribution, only partly due to dipolar effects. From the Yb170 Mössbauer resonance measurements in YbFe2, the exchange field of the iron and the crystalline field, acting on Yb3+, have been derived.
Epr Investigations of Impurities in the Lanthanide Orthophosphates
Authors: Abraham M. M. , Boatner L. A. , Rappaz M. 
Published: March 2011

ABSTRACTLanthanide orthophosphates formed from elements in the first half of the 4f transition series are analogs of the monoclinic mineral monazite. The known geologic properties of this mineral make the general class of lanthanide orthophosphate compounds attractive substances for long-term containment and disposal of α-active actinide nuclear wastes. EPR spectroscopy has been used to investigate the structural properties and solid state chemical properties of impurities in these materials and to compare the characteristics of single crystals and polycrystalline bodies.
57Fe and 125Te Mossbauer Study of LiFeCo3TeO8 and LiFeNi3TeO8
Authors: Gerard Andre , Grandjean Fernande , Flebus Carlo 
Published: March 2011

ABSTRACT57 Fe and 125 Te Mössbauer data on the spinels LiFeNi3TeO8 and LiFeCo3TeO8 are presented. Structural information relating to site occupations by Fe, valency of Fe and Te and magnetic hyperfine fields are obtained from this study.
Quadrupole Hyperfine Interaction and Magnetic Hyperfine Field in Feocl and its Intercalates
Authors: Maeda Y. , Herber R. H. 
Published: March 2011

ABSTRACTFeOCl is a layered compound belonging to the orthorhombic space group Pmnm (D2h13), with two formula units per unit cell. Adjacent layers in the (010) crystallographic plane, in which chlorine atoms face each other, are held together by van der Waals forces which are readily disrupted by the insertion of appropriate Lewis base molecules. This intercalation of “guest” species causes an expansion in the b-direction, leaving the remainder of the unit cell dimensions unchanged. Among base molecules which are readily intercalated are NH3, pyridine and a wide variety of substituted pyridines, nitrogen containing heterocyclic molecules, phosphines and phosphites. The limiting stoichiometry ranges from 1:3 (“guest” to Fe atom ratio) for small intercalants to 1:6 for large “guest” molecules. Using both powder X-ray diffraction and temperature dependent 57 Fe Mössbauer effect spectroscopy, the lattice dynamics, hyperfine interactions, magnetic ordering temperature and magnetic hyperfine field (at 4.2 K) have been studied for the neat matrix and a number of base intercalates. The magnetic hyperfine field at the iron atom at 4.2 K is 441╪3 KOe, independent of the magnitude of the b-axis expansion. Vzz is negative for neat FeOCl and intercalates in which the “guest” to host ratio is ≤ 1:3, and positive when this ratio is ≥ 1:4.
New Method for the Determination of Diffusion Constants from Partially Narrowed Nmr Lines
Authors: Wolf D. 
Published: March 2011

ABSTRACTThe effect of atomic and molecular motions on the NMR free-induction decay (FID) and lineshape is investigated theoretically in the intermediate temperature range in which the NMR line is only partially narrowed. It is shown that the FID may be decomposed into the weighted sum of a rigid-lattice (background) contribution and an exponentially decaying part containing all the information on the diffusive or reorientational motions in the crystal in terms of the spin-spin relaxation time T2.
A Method for Determining Impurity-Host Force-Constant Ratios
Authors: Kolk Berend 
Published: March 2011

ABSTRACTOne of the parameters of interest in studies on dilute alloys is the ratio of the effective host-host to impurity-host interaction. A method is presented which allows the evaluation of the effective impurity-host force-constant ratio, A′/A, for substitutional, isolated, impurity atoms in a cubic lattice by combining recoilless-fraction data (Mössbauer effect) of the impurity atoms with x-ray– or neutron-diffraction data of the host lattice. With this method, values of A′/A are obtained for dilute 57Fe impurities in various hosts.
Nmr Techniques for Studying Ionic Diffusion in Solids
Authors: Ailion David C. 
Published: March 2011

ABSTRACTA survey of NMR relaxation time techniques for studying ionic diffusion in solids is presented. Particular emphasis is placed on discussing the kinds of information obtainable from T1, Tlρ, TlD, and TlD' measurements. Applications to the study of local and nonlocal diffusion, diffusion in weakly magnetic systems, and motions between unequal potential wells are described. Relaxation due to fluctuating dipolar, quadrupolar, and chemical shift anisotropy interactions is discussed.
Material Characteristics of InGaAsP/InGaP Lasers
Authors: Yoo Jae S. , Ko Young T. , Park Georgui , Kim Tae I. , Kang Kyung I. , Kim Han S. 
Published: March 2011

ABSTRACTA study of material and optical characteristics of InGaAsPAnGaP lasers grown on GaAs (100) substrate, Operating at λ = 0.8μm was carried out. The main features of InGaAsPAnGaP lasers over the conventional AlGaAs/aCAs; ones were not only stable epitaxial layer growth due to the aluminum-free material, but also strong resistance to the degradation. The other benefits of InGaAsP/inGaP laser over AlGaAs/GaAs one was the quantum-well structure growth by a simple version of liquid-phase epitaxy (LPE), which might be irnispensable to the high power operation of a semiconductor laser. The separate confinement heterostructure single quantum weil(SCH-SQW) InGaAsP/nGaP lasers were fabricated for the material charaterization of quaternary systen. The local temperature rise at the mirror facet of a InGaAsP/InGaP laser, which is the barometer of a reliable operation, was less than 30°C under even above 500 mW CW operation. We presumably attribute this low local temperatur rise of the quaternary system to the fact that it has thenodynamically stable minor facet. The surface analysis of InGaAsP layer by ESCA showed that the formation of indium oxide would prevent the elemental segragation constituting dangling orbital, which is common to A1GaAs material systems.
Formation of Long Wavelength InP Laser MESAS
Authors: Ren F. , Pearton S. J. , Tseng B. , Lothian J. R. , Constantine C. 
Published: March 2011

ABSTRACTNarrow (1 μm), deep (3.5 μm) laser mesas have been formed on 2”φ InP wafers using stepper lithography and dry etching techniques for both dielectric and semiconductor patterning. Contrast enhancement techniques produce excellent edge acuity and vertical sidewalls on the initial photoresist lines. Pattern transfer to the underlying SiO2 regrowth mask is achieved by ECR SF6/Ar dry etching at 1 mTorr and –100V, conditions which also retain the verticality of the mesa. The semiconductor is etched using an ECR Cl2/CH4/H2/Ar discharge at 0.3 mTorr and –80V, with the sample held at ∼ 150°C. The etch rate under these conditions is ∼1 μm/min, with a selectivity of ≥10:1 for the semiconductor over the dielectric mask. The smooth etched surface and low degree of damage make this process ideal for epitaxial regrowth. The uniformity of each process step is also acceptable (≤7%). Comparison of the elevated temperature Cl2/CH4/H2/Ar mixture with the more conventional room temperature CH4/H2 plasma chemistry will be given.
Dual Role of Tin Reaction Barrier in Gold-Based Metallization to GaAs
Authors: Piotrowska A. , Kaminska E. , Guziewicz M. , Kwiatkowski S. , Turos A. 
Published: March 2011

ABSTRACTThe formation of ohmic contacts to p-GaAs based on Au-Zn system comprising a TiN diffusion barrier has been investigated using 2 MeV He+ RBS and the specific contact resistance measurements. It has been proved that TiN films deposited by reactive RF bias magnetron sputtering serves two purposes. First it suppresses the arsenic evaporation and thus confines the reaction between AuZn and GaAs. Second, it prevents intermixing between p-GaAs/Au(Zn) ohmic contact and an overlayer of Au.
Pd/Ge Contacts to n-TYPE InP
Authors: Jian Ping , Ivey Douglas G. , Bruce Robert , Knight Gordon 
Published: March 2011

ABSTRACTMultilayer metallizations of Pd/Ge/Pd, with different thickness ratios of Ge and Pd, were deposited onto n-type InP by means of electron beam evaporation. The specimens were then annealed in flowing N2 gas at temperatures ranging from 250 to 425°C for various times. Transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDX) and electron diffraction were used to identify the phase changes during reaction. The four point probe method was used for electrical resistance measurements. A Pd-In-P amorphous phase and a Pd2Ge compound formed during deposition. Subsequent annealing resulted in crystallization of the amorphous phase followed by epitaxial growth of Pd2InP(II) on InP at 350°C. At 425°C, Pd2InP(II) with Ge in solution, decomposed producing a contact with a lower specific contact resistance. The lowest contact resistances achieved were ∼10−5 Ωcm2. Further annealing led to more decomposition of InP, including presumably the Ge doped InP surface region, which corresponded to an increase in contact resistance.
The EFfects of Elemental Sequence and Pairing on Interdiffusion and Phase Formation of Al-Ge-Ni Ohmic Contacts for (001) GaAs
Authors: Lampert W. V. , Haas T. W. , Holloway Paul H. 
Published: March 2011

ABSTRACTThe growth sequence of Al, Ge, and Ni metals has been shown to dramatically affect the amount of heat treatment time required to convert the ohmic contact metallization from Schottky to ohmic behavior. Interpretation of interdiffusion and phase formation of the Al-Ge, Al-Ni, or Ni-Ge thin film couples were measured. Auger depth profiles and thin film X-ray diffraction were used to determine interdiffusion and phase formation resulting from various types of thermal processing. The effects of interdiffusion and formation of phases such as Ni-Ga, Ni-As, Ni-Ga-Ge, and Ni-As-Ge from the two element metallizations on GaAs will be used to explain the origin of ohmic behavior for the ternary Al-Ge-Ni contacts to GaAs.