bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lattice Site Location Studies of Rare-Earths Implanted in ZnO Single-Crystals
Authors: Rita Elisabete M.C. , Wahl Ulrich , Lopes Armandina L. , Araújo João P. , Correia João G. , Alves Eduardo , Soares José C. , Collaboration Isolde 
Published: April 2011

ABSTRACTIn this work we report on the lattice site location of rare earths in single-crystalline ZnO by means of the emission channeling (EC) technique. Following low dose (3×1013at/cm2) 60 keV ion implantation of the precursor isotope 169Yb, a position-sensitive electron detector was used to monitor the angular distribution of the conversion electrons emitted from 169Tm* as a function of the annealing temperature up to 600°C in vacuum. An additional annealing at 800°C in flowing O2 was performed. The EC measurements revealed that around 95–100% of the rare earth atoms occupy substitutional Zn sites up to an annealing temperature of 600°C/vacuum. After the 800°C/O2 annealing, the emission channeling effects decreased considerably.
Deposition of II/VI thin films from Novel Single-Source Precursors
Authors: Afzaal Mohammad , Malik Mohammad Azad , O'Brien Paul , Park Jin-Ho 
Published: April 2011

ABSTRACTThe compound [MeCd(SePiPr2)2N]2 is used as a single-source precursor to cadmium selenide films in a low-pressure chemical vapour deposition process. Thermogravimetric analysis (TGA) shows that the precursor is reasonably volatile, making it suitable for the deposition of thin films. As-deposited films were identified as CdSe confirmed by X-ray powder diffraction (XRPD) and their morphologies were studied by scanning electron microscope (SEM).
DLTS studies of defects produced in n-type silicon by hydrogen implantation at low temperature
Authors: Sugiyama Takahide , Ishiko Masayasu , Kanazawa Shigeki , Tokuda Yutaka 
Published: April 2011

ABSTRACTMetastable defects are discovered in hydrogen-implanted n-type silicon. Hydrogen implantation was performed with the energy of 80 keV to a dose of 2×10 cm- at 109 K. After implantation, the sample temperature was raised to room temperature. DLTS measurements were carried out in the temperature range 80–290 K for fabricated diodes. When the sample is reverse-biased at 10V for 10 min at room temperature and then is cooled down to 80 K, three new peaks labeled EM1, EM2 and EM3 appear around 150, 190 and 240 K, respectively. The introduction of metastable defects is found to be characteristic of low temperature implantation. We have evaluated properties of EM1 in detail. EM1 with thermal emission activation energy of 0.29 eV has a peak in concentration around the depth of 0.64 μ m, which corresponds to the projected range of 80 keV hydrogen. EM1 is regenerated with the reverse bias applied around 270 K and is removed with the zero bias around 220 K.
Mesoscopic study of the electronic properties of thin polymer films
Authors: Ribeiro Ricardo M. , Ramos Marta M. D. , Almeida A. M. , Correia Helena M. G. , A Jaime Silva , Stoneham M. 
Published: April 2011

ABSTRACTConjugated polymers are very interesting for light emitting diodes. Further improvement in device performance requires a better understanding on the correlation between the polymer structure and device characteristics. A mesoscopic study using a generalised Monte Carlo method of bipolar charge transport in thin poly(p-phenylene-vinylene) (PPV) films is presented in this paper. We show that energy and spatial molecular disorder have a serious influence on migration of charge carriers within the polymer layer. The transfer of carriers between two polymer chains is made dependent on the chemical potential difference as well as on other features such as the distance between both molecules involved and the direction of the electric field. The purpose of the present work is to clarify the effects of local energy and polymer structural disorder on current flow, trapping and recombination on polymer based devices.
Ti/Ni/Au/Diamond MIS Field Effect Transistors With TiO2 Gate Dielectric
Authors: Cai Yuhong , Christou Aris 
Published: April 2011

ABSTRACTTi/Ni/Au/diamond metal-insulator-semiconductor field effect transistors with TiO2 gate dielectric have been successfully fabricated. In this work, multi-layer metallization on the semiconducting diamond surface was investigated. Post-metallization annealing was performed and EDS analysis was conducted both before annealing and after annealing. Elevated temperature annealing accelerates the diffusion between multi-layer metal and lowers the ohmic contact resistance of the interface. Current-voltage characteristics of the transistor are reported.
Far Infrared Spectroscopy of In0.53Ga0.47As Quantum Wells on InP(100)
Authors: Rowell N. L. , Lockwood D. J. , Poole P. J. , Yu G. 
Published: April 2011

ABSTRACTPolarized far infrared reflectance was measured at oblique incidence for In0.53Ga0.47As / InP multiple quantum wells grown by chemical beam epitaxy on InP(100) wafers. Both the well thickness (0.25 - 20 nm) and number of periods (10 - 40) were varied. The reflectance spectra contained sharp Berreman modes at the frequencies of the transverse (TO) and longitudinal (LO) optical phonons. The contributions of the individual phonons were resolved with the model fits. Interface layer phonon modes were observed with intensity increasing with number of wells. The interface layers were 0.6 nm thick and of different composition to adjoining wells consistent with cross-sectional scanning tunneling microscope results on the same samples. The variation due to phonon confinement of the InAs- and GaAs-like LO and TO phonon frequencies was obtained.
Precessional strategies for the ultrafast switching of soft and hard magnetic nanostructures
Authors: Devolder T. , Belmeguenai M. , Schumacher H. W. , Chappert C. , Suzuki Y. 
Published: April 2011

ABSTRACTWe discuss the precessional, quasi-ballistic switching of magnetization in magnetic nanostructures. In soft spin-valve cells, fast and energy-cost effective magnetization switching can be triggered by a transverse field pulse of moderate amplitude, below the in plane anisotropy field, because of an amplification effect brought by the demagnetizing field at the early stage of the reversal. The same effect is no more possible in hard nanomagnets with perpendicular easy magnetization axis. We propose a new type of nanostructured magnetic device, designed to overcome this limitation. The speed is obtained through the use of a very high effective magnetic field, obtained by incorporating a significant exchange field which stores the energy in the form of a constrained domain wall surrounding a region of high magnetic anisotropy. This stored energy is partially available to accelerate the magnetization reversal in a precessional scenario. We illustrate the concept by studying numerically a model system. The key parameter for the reversal is the ratio of the domain wall width to the structure lateral dimension. Possible routes for device preparation are discussed. Promising application to magnetic storage are anticipated.
Nanoscale analysis of a Co-SrTiO3 interface in a Magnetic tunnel junction
Authors: Maurice J.-L. , Pailloux F. , Imhoff D. , Contour J.-P. , Barthélémy A. , Bowen M. , Colliex C. , Fert A. 
Published: April 2011

ABSTRACTWe use High Resolution Electron Microscopy together with Electron Energy Loss Spectroscopy to analyze the crystallography and the chemical configuration of a Co/SrTiO3 interface in a Co/SrTiO3/La2/3Sr1/3MnO3 magnetic tunnel junction.PACS: 75.47.-m, 75.70.Cn, 68.37.Lp, 79.20.Uv
Sm Doping Effects on Electrical Properties of Sol-Gel Derived SrBi2Ta 2O9 Films
Authors: Tokumitsu Eisuke , Kishi Masahito 
Published: April 2011

ABSTRACTWe have characterized (Sr,Sm)Bi2Ta 2O9 (SSBT) films fabricated by the sol-gel technique on Pt/Ti/SiO2/Si substrates. For ferroelectric-gate FET applications, a ferroelectric film which has a small remanent polarization and a relatively large coercive field is required. It is demonstrated that Sm doping in ferroelectric SBT films is effective to reduce the remanent polarization and enhance the coercive field. Sr0.5Sm0.2Bi2.2Ta2O9 films (150nm) crystallized at 850°C exhibits good electrical properties with a remanent polarization of 1.7 μC/cm2 and a coercive fields of 85 kV/cm. These values are suitable for ferroelectric-gate FET applications.
Thin-Film Indium Oxide Doped with Refractory Metals
Authors: Yoshida Yuki , Warmsingh Chollada , Gessert Timothy A. , Perkins John D. , Ginley David S. , Coutts Timothy J. 
Published: April 2011

ABSTRACTThe electrical and structural properties of sputtered indium oxide (In2O3) thin films doped with Mo, Zr, and Ti were studied. Properties of these films are compared to undoped In2O3 and tin-doped In2O3 (ITO). The as-sputtered films, doped with Mo (IO:Mo), exhibited high mobility (45 cm2V-1s-1). Pulsed laser deposition (PLD) was also used to deposit IO:Mo films. The highest mobility achieved for an as-deposited PLD IO:Mo film deposited onto a glass substrate was 42.7 cm2V-1s-1. However, PLD IO:Mo films deposited on single-crystal yttria-stabilized zirconia (YSZ) substrates exhibited a higher mobility of 53.6 cm2V-1s-1 and a greater degree of structural orientation than the sputtered films. Following post-deposition annealing, both the sputtered films on glass, and the PLD films on YSZ, exhibited improved mobilities of 47 and 66 cm2V-1s-1, respectively.
Experimental and Theoretical Studies of the Si(100)/SiO2 Interface Formed by Wet and Dry Oxidation
Authors: Chowdhuri A. Roy , Jin Dong-Un , Takoudis C. G. 
Published: April 2011

ABSTRACTInterfacial strain and substoichiometric silicon oxides are the two principal causes that result in the redshift of the transverse and longitudinal optical phonons of the asymmetric stretch of O in the Si-O-Si bridging bond of thermal SiO2 with decreasing oxide thickness. Analyses to comprehend these effects, therefore, require consideration of both strain and interfacial substoichiometry. A method to isolate the contributions of strain and suboxide content towards the observed shifts is proposed. The procedure, which utilizes simple optical model and effective medium approximation, allows estimation of the average strain and suboxide concentration in films of different thickness. Analyses of oxides formed at two different temperatures (550 and 700°C) with dry and wet oxygen reveal how process conditions affect the interface properties.
In Situ Thin Film Stress Measurements – A Path to Understanding the Structure and Morphology of Electron Beam Evaporated ZnS
Authors: Barrioz Vincent , Irvine Stuart J. C. , Paul D. 
Published: April 2011

ABSTRACTZnS is a material of choice in the optical coating industry for its optical properties and broad transparency range. One of the drawbacks of ZnS is that it develops high compressive intrinsic stress resulting in large residual stress in the deposited layer. This paper concentrates on the evolution of residual stress reduction in ZnS single layers, depending upon their deposition rate or the substrate temperature during deposition (i.e. 22 °C and 133 °C). The substrate preparation is addressed for consideration of layer adhesion. Residual stress of up to − 550 MPa has been observed in amorphous/poor polycrystalline ZnS layers, deposited on CMX and Float glass type substrates, by electron beam evaporation at 22 °C, with a surface roughness between 0.4 and 0.8 nm. At 133 °C, the layer had a surface roughness of 1 nm, the residual stress in the layer decreased to − 150 MPa, developing a wurtzite structure with a (002) preferred orientation. In situ stress measurements, using a novel optical approach with a laser-fibre system, were carried out to identify the various sources of stress. A description of this novel in situ stress monitor and its advantages are outlined. The residual stress values were supported by two ex situ stress techniques. The surface morphology analysis of the ZnS layers was carried out using an atomic force microscope (AFM), and showed that stress reduced layers actually gave rougher surfaces.
Preparation of Plate-Like Bulk Beta Iron-Disilicide Crystals Using Metal to Semiconductor Phase Transition by Heat Treatment
Authors: Osamura Masato , Ishihara Hidetaka , Liu Zhengxin , Tanoue Hisao , Sakuragi Shirou. , Hoshino Yasushi , Nakayama Yasuhiko , Makita Yunosuke 
Published: April 2011

ABSTRACTPlate-like β-FeSi2 bulk crystals with size of 10×10 mm2 and thickness of 1 mm were fabricated by annealing CVT (chemical vapor transport)-grown plate-like α-Fe2Si5 at 800°C in Ar atmosphere. Before annealing, α-Fe2Si5 crystals were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM) to be single crystals with flat surfaces. XRD measurements of β-FeSi2 crystals subjected to annealing showed that they had a po lycrystalline structure. The mean Fe/Si co mposit ion rat io of β-FeSi2 crystal measured by energy dispersive x-ray spectroscopy (EDX) was 31/69 and it was the same as that of α-Fe2Si5 bulk crystal before annealing. SEM, Raman scattering and electron probe micro-analysis (EPMA) measurements identified that there existed small Si precipitates mixed in the matrix of β-FeSi2 crystals. At annealing temperature of 800°C, the plate-like β-FeSi2 bulk was obtained even the annealing duration time was as short as 5 hours.
Oxide Structures formed on Silver Single Crystals due to Hyperthermal Atomic Oxygen Exposure
Authors: Li Long , Yang Judith C. 
Published: April 2011

ABSTRACTSilver (100) and (111) single crystals were exposed to a unique laser detonation atomic oxygen source, which produces a high flux of 5 eV atomic oxygen, for seven hours at 220°C. The resultant oxide and oxide-metal interfaces were characterized by optical, scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HREM). The oxide scale was more than 10-micron thick and very weakly attached to the Ag substrate. The silver oxides were complex and surprising, differ in their thickness and the oxide phases due to the orientation of the Ag single crystals. The cross-section TEM studies revealed complex microstructures with many defects, such as micro-twins, porosity and irregular shaped grains.
Electrochemical Properties Of Copper Oxide Surfaces, Buried Interfaces, And Subsurface Zones And Their Use To Characterize These Entities
Authors: Cocke David L. , Hossain Mohammad A. , Mencer Donald E. , McWhinney Hylton , Parga Jose R. , Mollah Mohammad Y. A. , Naugle Donal , Kesmez Mehmet 
Published: April 2011

ABSTRACTElectrochemistry of oxides is an expanding area of oxide characterization. Although, interfacial characterization techniques including surface science methods have contributes substantially to our current understanding of the processes involved in the oxidation of metals and alloys. The characterization of subsurface zones and buried interfaces still remain a major challenge. Copper reactions with oxygen have been studied by high vacuum based techniques of AES, ELS, ISS, XPS. SIMS, LEED. STM, SEXAFS, HEIS and PFDMS and with optical methods, like UV-Vis-NIR, diffuse reflectance spectroscopy, FTIR and photoluminescence spectroscopes. However it has become evident that the processes that produce thermally and plasma grown oxide films on metals and alloys are electrochemical in nature and can be modeled by electrochemical concepts. Therefore, it is important that the oxide over layers, thin films and thick films be characterized by electrochemical means -with electrochemical methods, such as linear potential sweep voltammetry, cyclis voltammetry, galvanostatic reduction and coulometry which allow the identification of copper (I), copper (II) and copper (III) oxides. Interest in copper as a technologically important material needs to be met with greater understanding of the fundamental nature of copper oxide structures. In this study, the authors demonstrate the use of Linear Sweep Voltammetry (LSV) to study buried structures in the thermally grown oxide layers on copper. In particular, LSV can be used to detact reactions at buried interfaces. It also recognizes Cu3O2 and the decomposition of copper oxides at the metal-oxide layers on copper. In particular, LSV can be used to detect reactions at buried interface. The two key parameters that drive oxide growth and decomposition are demonstrated to be oxygen activity and the free energies of formation of the oxides. The complex nature of the oxidation of copper, as well as other metals and alloys, will be described qualitatively using the Modified Cabrera-Mott (C-M) Model. Surface studies of oxidation of metals and alloys need to be supported and complemented by other techniques such as electrochemical methods.
Electrochemical Removal of Oxygen in amorphous Zr55Cu30Al10Ni5
Authors: Castellero Alberto , Bossuyt Sven , Chen George Z. , Lindsay Greer A. 
Published: April 2011

ABSTRACTContamination with oxygen is known to reduce the processability and otherwise affect the properties of Zr-based bulk metallic glasses (BMGs). Due to their affinity for oxygen, however, it is difficult and/or expensive to reduce the oxygen level in these materials. As a result, the glass-forming ability (GFA) of commercial-grade BMGs is significantly lower than that of research-grade materials. We present the application of a novel electrochemical method to this problem. The general principle is to remove oxygen from the material by direct electrochemical reduction in a molten-salt electrolyte. A cathode consisting of a porous metallic phase containing dissolved oxygen is submerged in a molten mixture of chlorides. When a current is applied, oxygen is ionised at the cathode, dissolved in the molten salt and discharged at the anode. We investigate thermodynamic and kinetic limitations to the reduction in oxygen content and the resulting improvement in GFA that can be achieved when this method is applied to glass-forming alloys such as Zr55Cu30Al10Ni5.
Undercooling And X-Ray Structural Studies Of Ti-Zr-Ni Liquids
Authors: Lee G.W. , Gangopadhyay A.K. , Kelton K.F. , Hyers R.W. , Rathz T.J. , Robinson M.B. , Rogers J. R. , Hennet L. , Krishnan S. 
Published: April 2011

ABSTRACTMaximum undercooling results for the icosahedral phase (i-phase), polytetrahedral C14 Laves phase, and solid solution phases are presented as a function of composition in Ti-Zr-Ni liquids. Containerless processing was achieved using the electrostatic levitation facility located at NASA/Marshall Space Flight Center. The maximum reduced undercooling decreases with increasing icosahedral short-range order in the ordered phase. The first synchrotron x-ray diffraction data from aerodynamically levitated liquids of Ti-Zr-Ni alloys suggest an icosahedral short-range order in the liquids, supporting Frank's hypothesis, correlating icosahedral order in the liquid with the nucleation barrier to the crystal phase. The strong negative heats of mixing between Ti/Zr and Ni and their relative atomic sizes likely favor the formation of this local icosahedral order.
A Thermodynamic Model for Amorphization and Topological Criteria
Authors: Senkov O.N. , Miracle D.B. , Rao S. 
Published: April 2011

ABSTRACTA thermodynamic model for amorphization is developed which allows analysis of the effect of composition, atomic radii, and elastic constants of constitutive elements on amorphization. The model is based on comparison of the Gibbs free energy and entropy of a defective crystal and undercooled liquid. The glass transition temperatures for thermodynamically unstable amorphous phases are determined as a function of topological parameters of an alloy. It increases with an increase in the atomic size of the solvent element and it has a maximum at a specific alloy composition. Topological criteria for alloy compositions that can produce a thermodynamically stable amorphous state are outlined and discussed.
Transient Deformation and Flow in Bulk Metallic Glasses and Deeply Undercooled Glass Forming Liquids — A Self-Consistent Dynamic Free Volume Model
Authors: Bossuyt Sven , Demetriou Marios D. , Johnson William L. , Lindsay A. 
Published: April 2011

ABSTRACTRecently, a self-consistent dynamic free volume model was proposed to analyze the Newtonian and non-Newtonian uniform steady-state flow data for bulk glass forming liquids such as those of the Zr-Ti-Cu-Ni-Be Vitreloy family. The model is based on the traditional free volume model of the glass transition, the Vogel-Fulcher-Tammann (VFT) equation, and a simple treatment of free volume production and annihilation during flow. It was shown that the model results in a simple one-parameter fit to extend the VFT equation for Newtonian flow to non-Newtonian uniform steady-state flow. We further extend the model to include transient uniform flow, by considering the evolution of free volume with time.
Grimsel Test Site - The Next Decades
Authors: Vomvoris Stratis , Kickmaier Wolfgang , McKinley Ian G. 
Published: April 2011

ABSTRACTThe Grimsel Test Site, which has been in operation since 1984, is known in the radioactive waste management community for the scope and quality of the experiments and projects performed over the last two decades. This paper will overview Nagra's commitments and the current plans for future activities in association with Grimsel, which are being developed considering time scales of the order of a decade or more.
Waste Form Release Calculations for Performance Assessment of the Hanford Immobilized Low-Activity Waste Disposal Facility Using a Parallel, Coupled Unsaturated Flow and Reactive Transport Simulator
Authors: Bacon Diana H. , Peter McGrail B. 
Published: April 2011

ABSTRACTA set of reactive chemical transport calculations was conducted with the Subsurface Transport Over Reactive Multi-phases (STORM) code to evaluate the long-term performance of a representative low-activity waste glass in a shallow subsurface disposal system located on the Hanford Site. Technetium, the main contributor to a drinking water dose, is assumed to be released congruently with the dissolution of the glass. Sodium is released at a higher rate via a kinetic ion-exchange reaction. Aqueous equilibrium reactions involving sodium and other dissolved glass constituents increase the pH, and hence the rate of glass dissolution. The precipitation of secondary minerals can also lower the amount of aqueous dissolved silica, which can increase the rate of glass dissolution. Predicted technetium release rates, however, remain several orders of magnitude lower than required by drinking water regulations.
Diffusion and Migration of Ions in Sedimentary Rock Matrix: Behaviour of Cesium and Iodide in Micropores of Sandstone
Authors: Sato Haruo , Muraoka Tamotsu 
Published: April 2011

ABSTRACTIn-diffusion experiments for Cs+ and I- in sandstone were performed as a function of ionic strength of porewater ([NaCl] =0.01, 0.51M) and tracer concentration ([Cs1] =7.5E-5, 1.5E-2M) together with the measurements of the fundamental properties of sandstone, and apparent diffusivities (Da) and rock capacity factors (α) for Cs+ were obtained. The obtained Da-values for Cs+ were scarcely dependent on [NaCl], but increased with increasing [Cs+]. This trend is consistent with that of α-values, indicating that although effective diffusivity and distribution coefficient scarcely depend on [NaCl], those depend on [Cs+]. The concentration profiles of I- were all in breakthrough. Although this indicates that I- diffusion is faster than that of Cs+, the concentration profiles of I- may have been lower than those for blank samples.