bluuebunny/crossref_metadata_2025_split huggingface dataset:
X-Ray Crystal Diffraction Study of Zr,Na-β-Alumina
Authors: Pearson Wayne H. , Lomax Joseph F. 
Published: March 2011

AbstractThe reaction of crystalline lithium-stabilized Na-β”-Alumina with zirconium(IV) chloride at 400°C for 303h has caused sodium ions to exchange with zirconium ions. An X-ray crystal diffraction study of both the parent lithium stabilized Na-β”-alumina (1) and the partially zirconium exchanged product (2) have been made at 147 K. Crystal data for 1: rhombohedral, R 3 m, a = 5.6037 (3), c = 33.6210 (86) Å, V = 914.31 (24) Å3. Crystal data for 2: rhombohedral, R 3 m, a = 5.5994 (5), c = 33.7711 (51) Å, V = 916.96 (16) Å3. Zirconiums in 2 reside, predominately, in the Beevers-Ross type site.
Fast-Ion Conduction and Disorder in Cation and Anion Arrays in Y2(Zry Ti1−y)2O7 Pyrochlores Induced by Zr Substitution: a Neutron Rietveld Analysis
Authors: Heremans C. , Wuensch B.J. , Stalick J.K. , Prince E. 
Published: March 2011

AbstractStructural refinements have been carried out on the Y2(ZryTi1−y)2O7 system for increasing amounts of Zr substitution. The structure changes from an ordered pyrochlore structure (superstructure of the fluorite structure) to an anion-deficient fluorite structure. Separate processes govern the disordering of the cation and anion arrays. In particular, the anions begin to disorder at lower values of y than the cations. For intermediate compositions, a minor amount of fluorite phase coexists with the primary partially-disordered pyrochlore phase.
XPS Spectra and Optical Reflectivity of Yttrium Stabilised Zirconia
Authors: Camagni P. , Depero L.E. , Parmigiani F. , Samoggia G. , Sangaletri L. , Scagliotri M. 
Published: March 2011

AbstractX-ray photoelectron spectroscopy measurements and synchrotron radiation reflectivity and measurements in the photon energy range between 5eV and 30 eV are reported for yttrium stabilised zirconia single crystals. From the present data some behaviour of the valence band and conduction band electronic structure are elucidated. Two features present in the valence band XPS spectra, not explained on the basis of one-clectron theory, are tentatively assigned to simultaneous two electron excitation.
Potassium Beams from Solid State Electrochemical Cells
Authors: Bruce P.G. , Roy S. , Stewart H. , Prior K. A. 
Published: March 2011

AbstractA solid state electrochemical cell, K1-xFe11O17/potassium beta-alumina/metal gauze, is presented which is capable of producing a beam of potassium vapour. The generation of potassium vapour has been demonstrated and the cell has been used to dope ZnSe during growth of the chalcogenide by molecular beam epitaxy, thus forming p-type ZnSe. The electrochemical source has the advantage that the potassium flux is controlled by the current passing through the cell and eliminates the need to handle potassium metal. Cyclic voltammetric measurements at 350'C suggest that potassium metal is first generated electrochemically by a mechanism of nucleation and growth, then evaporates from the cell.
AFM Imaging of the Crystalline-To-Amorphous Transition On the Surface of Ion-Implanted Mica
Authors: Eby Ray K. , Henderson Grant S. , Wicks Fred J. , Arnold George W. 
Published: March 2011

AbstractScanning microscopy is the only technique available for directly imaging the short-range structural features of the crystalline-to-amorphous (C-A) transition. Cleaved sheets of muscovite were implanted with 600 keV argon ions in order to induce radiation damage; thus producing the C-A transition. AFM images of Ar-implanted muscovite show the surface structural features of the C-A transition. Low-resolution images show a progressive increase in the surface roughness of muscovite with increasing ion dose, as seen by the development of hummocky microtopography, whose individual hummocks are 25 nm across. High-resolution AFM images of unimplanted muscovite reveal a highly crystalline structure, as shown by the hexagonal arrangement of the (SiO4)-tetrahedral layers. By scraping through the uppermost surface layer of the implanted samples, using a cantilever forces of 50 - 100 nN, the C-A transition is recognized by a decrease in the long-range order of the tetrahedral layers. Accordingly, crystal defects and highly disordered regions increase in frequency and size with Ar-dose. At the highest Ardose, disordered regions dominate the structure, lending complications to AFM image interpretation. Surface hardness decreases with higher radiation doses, as evidenced by the greater ease of scraping through atomic layers in the more damaged samples.
AFM Imagings of Ferritin Molecules Bound to LB Films of Poly-1-Benzyl-L-Histidine: Imaging the ordered arrays of water-soluble protein ferritin with the atomic force microscope
Authors: Ohnishi Satomi , Hara Masahiko , Furuno Taiji , Knoll Wolfgang , Sasabe Hiroyuki 
Published: March 2011

AbstractA water-soluble protein, ferritin, on a silicon surface has been imaged in pure water at room temperature with the atomic force microscope (AFM). The samples were prepared by binding ferritin molecules electrostatically to a charged polypeptide layer of poly-l-benzyl-L-histidine (PBLH). The hexagonal arrangement of ferritin molecules was imaged with high reproducibility, since the force between tip and the sample surface could be kept sufficiently lower than 10-10 N. The applied force can be stabilized and weakened mainly due to a “self-screening effect” of the surface charges of the ferritin-PBLH layer. We demonstrate that the electrostatic-binding sample preparation is one of the suitable methods for soft biological specimens to achieve the nondestructive. low-force AFM imagings.
Surface Structure of Oxide Catalyst Microcrystals: High Resolution Electron Microscopy Study
Authors: Kryukova G. N. , Chuvilin A. L. , Sadykov V. A. 
Published: March 2011

AbstractThe surface structure of “pure” oxides as well as the same materials after promotion by alkali metals, models of the oxide surface based on results of image simulation procedure have been proposed. The surface structure reconstruction of the catalysts upon electron beam irradiation was also observed. For the specimens under investigation surface steps and kinks were shown to be essential for strong interaction between oxides and supported Pt particles preventing their migration and suppressing the sintering process.
In-Plane Asymmetries on the Ge(111)-c(2×8) Surface Mapped with the Scanning Tunneling Microscope
Authors: Molinàs-Mata P. , Zegenhagen J. , Böhringer M. , Takeuchi N. , Selloni A. 
Published: March 2011

AbstractWe report on new experimental studies of the Ge(111)-c(2×8) reconstruction performed with low-energy electron diffraction. (LEED) and scanning tunneling microscopy (STM). Weak quarter-order reflections are present in the c(2 × 8) LEED pattern in agreement with previous observations and results of ab initio calculations. In order to gain insight into the predicted splitting of dangling bond states, we compare constant current topographs (CCT's) performed at high-tunneling currents (40.nA) with first-principles calculations of the local density of states (LDOS) 1Å above the surface adatoms and obtain good qualitative agreement. We finally discuss to what extent the STM CCT's at high tunneling currents (small sample-tip distances (STD)) are sensitive to surface states outside the Г point.
Effect of the Angular Momentum and Magnetic Quantum Numbers on Auger and Photoelectron Scattering
Authors: Ramaker D. E. , Yang H. , Idzerda Y. U. 
Published: March 2011

AbstractAngle-resolved electron intensity distributions for Auger and photo- electrons are calculated using a curved-wave electron scattering formalism and compared with experiment. The distributions are found to depend significantly on both the ℓ and mℓ quantum numbers of the scattered electron. We consider the simple metals Ir and Al. Although the intensity patterns depend strongly on the ℓ quantum number at relatively low energy, even at high energies (around 1500 eV), a significant ℓ effect remains, which we find arises from nearest neighbor single scattering and from the multiple scattering or defocussing effect. The relative contribution of each ℓ and mℓ partial wave is determined not only by the quantum mechanicaf matrix elements, but also by the energy, polarization, and direction of the excitation beam.
Atomic Force Microscopic Imaging of Biologically Important Materials
Authors: Siperko Lorraine M. , Landis William J. 
Published: March 2011

AbstractAtomic force microscopy (AFM) has been used to image the surface atomic structure of hydroxyapatite [Ca10(PO4)6 (OH)2], HA, and brushite [CaHPO4 · 2H2O], DCPD. Compared to HA, the surface of DCPD was found to be much less complex. Identification has been made of one crystal plane of DCPD that has atoms commensurate with those of one of the observed crystal planes of HA.
Characterization of Internal Interfaces by Atom Probe Field Ion Microscopy
Authors: Miller M. K. , Jayaram Raman 
Published: March 2011

AbstractThe near atomic spatial resolution of the atom probe field ion microscope permits the elemental characterization of internal interfaces, grain boundaries and surfaces to be performed in a wide variety of materials. Information such as the orientation relationship between grains, topology of the interface, and the coherency of small precipitates with the surrounding matrix may be obtained from field ion microscopy. Details of the solute segregation may be obtained at the plane of the interface and as a function of distance from the interface for all elements simultaneously from atom probe compositional analysis. The capabilities and limitations of the atom probe technique in the characterization of internal interfaces is illustrated with examples of grain boundaries and interphase interfaces in a wide range of materials including intermetallics, model alloys, and commercial steels.
The Origins of High Spatial Resolution Secondary Electron Microscopy
Authors: Scheinfein M. R. , Drucker J. S. , Liu J. , Weiss J. K. , Hembree G. G. , Cowley J. M. 
Published: March 2011

AbstractThe secondary electron generation process is studied in an ultra-high vacuum scanning transmission electron microscope using electron coincidence spectroscopy. Production pathways for secondary electrons are determined by analyzing coincidences between secondary electrons and individual excitation events. The ultimate spatial resolution available in scanning electron microscopy is limited by the delocalization of the secondary electron generation process. This delocalization is studied using momentum resolved coincidence electron spectroscopy. The fraction of secondary electrons resulting from localized excitations can explain the high spatial resolution observed in secondary electron microscopy images.
Coal and the Moessbauer Effect
Authors: Montano Pedro A. 
Published: March 2011

ABSTRACTThe presence of iron bearing minerals in coal makes the Moessbauer effect extremely useful as an analytical tool. In this paper we present a general review of the use of Moessbauer spectroscopy in coal research. We discuss a simple method to identify iron bearing minerals in coal. Several researchers have used the Moessbauer effect to study the transformations of iron minerals during coal processing. We have studied the stoichiometries of iron sulfides produced during coal liquefaction. We found drastic changes in the stoichiometry of the pyrrhotites as a function of the total sulfur content of the coal, and the reaction conditions. Some in situ experiments are reported in this paper. We have observed evidence of reactions between the coal components and the iron sulfides at high temperatures (400° C). The possibility of studying in situ reactions makes the Moessbauer effect a unique analytical tool.
NMR of Small Platinum Particles
Authors: Stokes Harold T. , Rhodes Howard E. , Wang Po-Kang , Slicuter Charles P. , Sinfelt J. H. 
Published: March 2011

ABSTRACTWe present 195Pt NMR lineshapes as well as relaxation data in three different samples of platinum metal particles (46%, 26%, and 15% dispersion) supported on alumina. We show that the electronic properties of these particles are very much different from those of bulk Pt metal. A prominent peak in the lineshape has been identified as a “surface resonance” which arises from Pt nuclei on the surface of the Pt particles. We find that these surface Pt atoms are “nonmetallic” when coated with adsorbed molecules.
Motional Correlation Time of Dilute 111Cd Impurities in Se-Rich Liquid Se-Te Alloys
Authors: Gaskill D. K. , Gardner J. A. , Krane K. S. , Krusch K. , Rasera R. L. 
Published: March 2011

ABSTRACTThe motional correlation time, τc, in liquid Se and Se-rich Se-Te alloys has been investigated between 500 and 900°C using time differential perturbed angular correlations of y-rays from dilute 111Cd impurities. In all alloys we find τc ∝ exp (E0/kT) at low T where E0 = 0.36 eV. τC deviates from this relation at high T. At low T, τCis tentatively identified as the lifetime of a Cd to host molecule bond, and at high T as the average lifetime of bonds in the host molecule.
Study of Internal Indium Oxidation in Silver by TDPAC
Authors: Pasquevich A. F. , Sánchez F. H. , Bibiloni A. G. , Massolo C. P. , López-García A. 
Published: March 2011

ABSTRACTInternal oxidation of indium in a silver matrix is studied by time-differential perturbed angular correlations. The oxidizer treatments were performed in air at 1 atm. Our results are consistent with the formation of different In-O complexes.
A Mössbauer Study of the Amorphous System (FexNi1−x)75P16B6Al3
Authors: Bjarman S. , Wäppling R. , Rao K.V. 
Published: March 2011

ABSTRACTIn the system (FeXNi1−x)75P16B6Al3 an unusual magnetic behaviour is found in the composition range 0.2<x<0.3. The drastic changes seen at low temperature in the thermomagnetic measurements is found not to affect the Mössbauer spectra. From the width of the magnetic hyperfine field distribution as function of temperature there seems to be a distribution in Curie temperatures. Due to the absence of spin texture it was not possible to make a distinction between the two proposed low temperature phases although the general results favour the spin glass alternative.
Isotope Effect on The Electronic Structure of Hydrogen in Metals
Authors: Jena P. , Satterthwaite C. B. 
Published: March 2011

ABSTRACTThe effect of the isotopic mass on the redistribution of electron charge and spin density around a light impurity such as hydrogen in metals has been studied. Considered in this review are: (a) the magnetic hyperfine coupling to the hydrogen nucleus and the effect of isotopic mass, (b) the isotope effect in hydrogen impurity resistivity, (c) the reverse isotope effect in superconducting PdH(D) and (d) the thermally induced detrapping of hydrogen from the vicinity of solute sites in metallic hosts.
Electron Spin Resonance Studies of Amorphous Silicon
Authors: Biegelsen David K. 
Published: March 2011

ABSTRACTElectron spin resonance and related spin dependent measurements have been used to make key contributions to the understanding of amorphous silicon, specifically as probes of the dominant states in the gap, recombination processes and doping. In this paper we give a cursory description of the techniques as they apply to this problem. We then review what has been learned in a-Si:H usually from coupled results of spin resonance and other complementary experimental techniques. The results lead us to a surprisingly simple picture of the equilibrium and non-equilibrium behavior of defects and carriers in this prototypical amorphous semiconductor.
Integration of a Quantum Well Laser with AlGaAs/GaAs-HEMT Electronics
Authors: Bronner W. , Hornung J. , Köhler K. , Olander E. , Wang Z.-G. 
Published: March 2011

ABSTRACTIn this presentation the various technology steps for the monolithic integration of GaAs quantum well lasers with Double Pulse Doped AlGaAs/GaAs/AlGaAs Quantum Well (DPDQW) E/D HEMT electronics on a single substrate in one process run are described. All layers are grown by molecular beam epitaxy. The laser structure, consisting of three 74 Å GaAs quantum wells between two AlGaAs cladding layers, are grown on top of the electronic structure. The laser mesas and contact areas are defined by a combined wet and dry etch process. Apart from the transistor gates which are exposed by electron beam lithography, all lithography steps are performed using contact printing. A two layer metallization is used to interconnect the devices whereby air-bridges are used to connect the laser mesas to the electronics. First results showed laser action of laser diodes of area 3 x 300 μm2 at a threshold current of less than 60 mA, as well as the operation of different electronic devices on wafers which have been processed in this way. These include a laser diode driver, and an optoelectronic receiver with a MSM photo diode, both devices operating at a data rate of 5 Gbit/sec. These results indicate that the process sequence described is suitable for the integration of laser diodes and HEMT electronics.
Small Diameter Dry Etched Via Holes in GaAs
Authors: Pearton S. J. , Ren F. , Katz A. , Tseng B. , Lothian J. R. , Fullowan T. R. 
Published: March 2011

ABSTRACTTwo techniques for fabricating through-wafer via holes in 2-4 mil thick GaAs substrates were examined. In the first, Ni or thick photoresist masks were used for patterning 30 μm diameter vias by ECR-rf dry etching using low pressure (10-20 mTorr), low bias (– 150V) BCI3/C12 discharges. Microwave enhancement of these discharges produced faster etch rates but a greater degree of isotropic material removal at a given pressure. Reducing the process pressure produces extremely anisotropic features with high aspect ratio. The BC13-to-C12 ratio must be kept to ≥5:1 to maintain the anisotropy. A novel laser drilling technique was also examined - in this case a Q-switched beam with high energy density was used to ablate material in each pass of the beam, producing a via in approximately 40 passes. This is a maskless procedure capable of producing any desired via hole pattern, but currently there is no selectivity for ablating GaAs over a front-side metal film.
Electron Cyclotron Resonance CVD of Silicon Oxynitride for Optoelectronic Applications
Authors: Boudreau M. , Boumerzoug M. , Kruzelecky R. V. , Mascher P. , Jessop P. E. , Thompson D.A. 
Published: March 2011

ABSTRACTSilicon oxynitrides with compositions varying from Si3N4 to SiO2 were deposited on silicon substrates by electron cyclotron resonance plasma enhanced chemical vapour deposition (ECRPECVD). The silicon source used is an organic liquid, Tris Dimethyl Amino Silane (trade name SiN – 1000TM). Optical emission spectroscopy is used to characterize the ECR plasma, this information then is correlated with the optical properties of the deposited film, as determined by in situ ellipsometry. Auger electron spectroscopy showed that only low levels of carbon (< 3 at%) are present. The SiO2 and Si3N4 films are close to stoichiometric, with low levels of bonded hydrogen as determined by infrared absorption spectroscopy.Planar waveguide structures were fabricated and tested using the prism coupling technique to determine the mode effective indices. These are compared to those expected from the ellipsometry measurements.
Vacuum Integrated Fabrication of Buried Heterostructure Edge Emitting Laser Diodes
Authors: Hong M. , Vahkshoori D. , Grober L. H. , Mannaerts J. P. , Chu S. N. G. , Wynn J. D. , Freund R. S. 
Published: March 2011

ABSTRACTWe describe an in-situ fabrication process which combines electron cyclotron resonance (ECR) plasma H2 to clean native oxides, ECR SiCl4 to etch anisotropically, a brief Cl2 chemical etch to remove any near surface damage and contamination, and molecular beam epitaxial (MBE) regrowth. We report the first buried heterostructure (BH) AlGaAs/GaAs/InGaAs edge emitting laser diodes fabricated using this in-situ process. The lasers operate in continuous mode without noticeable degradation.
Influence of CH4/H2 Reactive Ion Etching on Deep Levels in Si-Doped AlxGa1−xAs (x=0.25)
Authors: Pereira R. , Van Hove M. , de Potter M. , Van Rossum K. 
Published: March 2011

The effect of CH4/H2 reactive ion etching (RIE) on Si-doped AlxGa1−xAs (x=0.25) is studied by deep level transient spectroscopy (DLTS) and Hall measurements. After RIE exposure, the samples were annealed between 250 and 500°C in order to study the recovery kinetics of deep and shallow levels. Non-etched reference samples showed broad DLTS spectra which were deconvoluted in two different emission peaks. We assigned them to DX1 and DX2 centers. The different deep levels are characierized by different aluminium configurations, one or two aluminium atoms, surrounding the silicon donor which are responsible for the DX centers. After RIE exposure and subsequent thermal annealing, a third emission peak is observed. This emission is attributed to the DX3 center, which is characterized by three aluminium atoms neighbouring the silicon donor. The recovery activation energy is calculated based on first-order kinetics. The activation energies are found to be around 1.9 eV in all cases.Complementary Hall measurements as a function of temperature (4-300 K) were used to characterize the electron capture of deep levels in Si-doped AlGaAs exposed to CH4/H2 RIE. We observed that the samples exposed to RIE and annealed at temperatures higher than 400°C exhibit electron capture in the 120-150 K temperature range. On the other hand, samples annealed at lower temperatures, showed additional capture features between 200 and 230 K.
Growth of Heterojunction Bipolar Transistors by Metalorganic Molecular Beam Epitaxy
Authors: Abernathy Cammy R. 
Published: March 2011

ABSTRACTHeterojunction bipolar transistors (HBTs) are becoming increasingly important for highspeed electronic applications. This paper will discuss how the unique growth chemistry of metalorganic molecular beam epitaxy (MOMBE) can be used to produce high performance HBTs. For example, it has been well documented that MOMBE's ability to grow heavily doped, well-confined layers of either n- or p-type is a significant advantage for this device. This feature arises primarily from the ability to use gaseous dopant sources in the absence of interfacial gas boundary layers. While this is an advantage for doping, it can be a disadvantage in other areas such as AlGaAs purity or InGaP lattice matching. This paper will discuss how these difficulties can be overcome through the use of novel Al or Ga precursors thus allowing deposition of high quality GaAs-based HBTs. By using trimethylamine alane (TMAA), background impurity concentrations can be reduced substantially. Further improvements in purity require cleaner Ga precursors or alternatively novel Ga substitutes. The resulting reduction in compensation allows for the use of lower dopant concentrations in the AlGaAs thus producing significant improvement in the leakage behavior of the base-emitter junction. Even further improvement can be achieved through the use of InGaP. Using novel Ga precursors, such as tri-isobutylgallium (TIBG), the problems associated with the sensitivity of composition to growth temperature are greatly reduced, allowing for the reproducible deposition of devices containing InGaP emitter layers.