bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoluminescence of Ge Nanoclusters in Ion Implanted SiO2
Authors: Lopes J.M.J. , Zawislak F.C. , Behar M. , Fichtner P.F.P. , Rebohle L. , Skorupa W. 
Published: April 2011

ABSTRACT180 nm thick SiO2 films produced by wet oxidation of (100) Si wafers were implanted at room temperature with 120 keV Ge+ ions at a fluence of 1.2×10 cm-2 in order to allow the formation of Ge nanoparticles upon post implantation thermal annealings within the interval 400°C ≤ T ≤ 900°C. The size and depth distribution of the Ge nanoparticles were characterized by Transmission Electron Microscopy and Rutherford Backscattering Spectrometry. In addition, the room temperature photoluminescence (PL) bands of the nanoparticles system were studied in the regions of the blue-violet and ultra-violet emissions. The mean diameter of the nanoclusters increases from 2.2 nm at 400°C to 5.6 nm at 900°C. Concomitantly, the blue-violet PL intensity increases by a factor of 12 within the same temperature interval. The results are discussed in terms of possible atomic mechanisms involved in the coarsening behavior and leading to the formation of luminescent centers.
Half-Integer Spin Molecular Nanomagnets
Authors: Hendrickson David N. , Christou George , Wernsdorfer Wolfgang , Hill Stephen O. , Aliaga-Alcade Núria , Bhaduri Sumit , Edwards Rachel S. , Aubin Sheila M. J. , Sun Ziming 
Published: April 2011

ABSTRACTSingle-molecule magnets (SMM) are molecules that function as single-domain nanomagnets. SMMs have been characterized with a ground-state spin ranging from S = 4 to S = 13. A few SMMs have been identified that have half-integer spin ground states. [Cation][Mn12O12(O2CR)16(H2O)4] complexes, where R is some substituent, are SMMs that have either a S = 19/2 or 21/2 ground state. Quantum tunneling of magnetization (QTM) is observed for these half-integer-spin Kramers [Mn12]- degenerate SMMs in zero external magnetic field, as well as for a class of S = 9/2 Mn4 SMMs. The presence of QTM in zero external field is attributed to a transverse component of a nuclear spin field, dipolar interactions and intermolecular exchange interactions. The Landau-Zener method is used to measure the tunnel splitting as a function of transverse magnetic field for a single crystal of the S = 9/2 SMM [Mn4O3(OSiMe3)(OAc)3(dbm)3]. Spin parity dependent QTM is established. The effect of a magnetic exchange interaction between two S = 9/2 Mn4 SMMs upon QTM was studied for another compound. The hydrogen bonding and Cl…Cl contacts within a supramolecularly linked [Mn4]2 dimer lead to a weak antiferromagnetic exchange interaction between the two S = 9/2 SMMs. This interaction causes a shift (exchange bias) from zero field for the magnetic field at which QTM occurs.
Bistable memory effect in chromium oxide junctions
Authors: Sokolov A. , Yang C.-S. , Ovtchenkov E. , Yuan L. , Liou S.-H. , Doudin B. 
Published: April 2011

ABSTRACTMagnetotransport properties of granular CrO2 /Cr2O3 films made of CrO2 crystals covered by 1– 2 nm native insulating Cr2O3 are presented. Electrical properties of a limited number of grains measured in series and parallel (10 to 15 grains) reveal intergrain tunneling characteristics. At lowest temperatures, a well pronounced zero bias anomaly indicates that impurities in the junctions block the electronic flow.Hysteresis in the IV curves are observed at intermediate temperatures on zero-field cooled samples. Changing the polarity of a short excitation pulse (100ns) of amplitude smaller than 1 V triggers a change in the zero-bias resistance by 10–50%. These states are stable and well reproducible in the temperature interval ranging from 100K to 250K. Applying an external magnetic field cancels the IV hysteresis. The resistance of the devices in the kΩ range, the potential high-speed for writing and reading the resistance sate, make these systems interesting candidates for magnetic non-volatile memories.
Ab-initio theory of CPP transport
Authors: Weinberger P. 
Published: April 2011

ABSTRACTThe phenomenon of electric transport perpendicular to the planes of atoms is discussed in terms of an ab-initio approach based on the Kubo-Greenwood equation. Since level of decription is fully relativistic “artifacts” due to spin resolution are avoided. Besides a formal discussion of the applied methods and an illustration of the numerical procedures, in particular the dependence of the magnetoresistance on the quality of interfaces, and issues concerning “tunneling” in metal/non-metal heterojunctions are discussed.
Magnetic Properties of Ni Nanoparticles Embedded in Amorphous SiO2
Authors: Fonseca Fabio C. , Goya Gerardo F. , Jardim Renato F. , Muccillo Reginaldo , Carreño Neftalí L. V. , Longo Elson , Leite Edson R. 
Published: April 2011

ABSTRACTA modified sol-gel technique was used to synthesize nanocomposites of Ni:SiO2 which resulted in Ni nanoparticles embedded in a SiO2 amorphous matrix. Transmission electron microscopy TEM analysis were performed to study the structure and morphology of the magnetic powders. The Ni particles were found to have a good dispersion and a controlled particle size distribution, with average particle radius of ∼ 3 nm. A detailed characterization of the magnetic properties was done through magnetization measurements M(T,H) in applied magnetic fields up to ± 7 T and for temperatures ranging from 2 to 300 K. The superparamagnetic (SPM) behavior of these metallic nanoparticles was inferred from the temperature dependence of the magnetization. The blocking temperature TB, as low as 20 K, was found to be dependent on Ni concentration, increasing with increasing Ni content. The SPM behavior above the blocking temperature TB was confirmed by the collapse of M/MS vs. H/T data in universal curves. These curves were fitted to a log-normal weighted Langevin function allowing us to determine the distribution of magnetic moments. Using the fitted magnetic moments and the Ni saturation magnetization, the radii of spherical particles were determined to be close to ∼ 3 nm, in excellent agreement with TEM analysis. Also, magnetic hysteresis loops were found to be symmetric along the field axis with no shift via exchange bias, suggesting that Ni particles are free from an oxide layer. In addition, for the most diluted samples, the magnetic behavior of these Ni nanoparticles is in excellent agreement with the predictions of randomly oriented and noninteracting magnetic particles. This was confirmed by the temperature dependence of the coercivity field that obeys the relation HC(T) = HC0 [1-(T/TB)1/2] below TB with HC0 ∼ 780 Oe.
Dynamic growth mechanism and interface structure of crystalline zirconia on silicon
Authors: Wang S J , Huan A C H , Ong C K 
Published: April 2011

ABSTRACTIn present report, we have studied the initial stage of the growth of crystalline yttria-stabilized zirconia (YSZ) films on the natively oxidized Si (100) wafer by pulsed-laser deposition. X-ray photoelectron spectroscopy (XPS) and high-resoluti on transmission electron microscopy (HRTEM) show that, for the first few monolayers of crystalline YSZ deposited on Si (100), the dynamic processes appear to be the decomposition of SiO2 to SiO, the formation of ZrO2, and the desorption of SiO. The native amorphous silicon oxide layer is removed completely with the continued deposition of YSZ and the oxygen in this layer is used as oxygen source for forming stable crystalline oxide film. XPS depth profile and HRTEM investigation showed that the interface of crystalline YSZ film in contact with silicon was found to be atomically sharp and commensurately crystallized without an amorphous layer. The interface structure is suggested to have a sequence of-Si-O-Zr-O-. For the film with electrical equivalent oxide thickness 1.46 nm, the leakage current is about 1.1×10- A/cm2 at 1 V bias voltage. The hysteresis and interface state density in this film are measured to be less than 10 mV and 2.0×1011eV-1cm-2.
X-ray Amorphous P-type Conductive Oxide; ZnRh2O4
Authors: Narushima Satoru , Mizoguchi Hiroshi , Ohta Hiromichi , Hirano Masahiro , Shimizu Ken-ichi , Ueda Kazushige , Kamiya Toshio , Hosono Hideo 
Published: April 2011

ABSTRACTAn amorphous p-type conductive oxide semiconductor was created based on a mother crystalline material, a p-type conductive ZnRh2O4 spinel. The amorphous film of ZnRh2O4 was deposited by an rf sputtering method. Seebeck coefficient was positive, +78 μVK-1, indicating that major carrier is a positive hole. A moderate electrical conductivity (2 S cm-1 at room temperature) for a p-type semiconductor was observed. Optical band gap was estimated to be 2.1 eV. P-n junction diodes with a structure of Au / a-ZnRh2O4 / a-InGaZnO4 / ITO fabricated on glass substrates, operated with a good rectifying characteristics, a rectification current ratio at ± 5V of ∼103. The threshold voltage was 2.1 eV, which corresponds to the band gap energy of the amorphous ZnRh2O4. This is the first discovery of a p-type amorphous oxide and the demonstration of p-n junction all composed of amorphous oxide semiconductors.
Photoemission Study of Interfacial Oxidation in ZrO2/subnanometer SiONx/Si(100) Stacked Structures
Authors: Miyazaki Seiichi , Yamashita Hiroki , Nakagawa Hiroshi , Yamaoka Masanori 
Published: April 2011

ABSTRACTFor staked structures consisting of evaporated ZrO2 and ∼0.6nm-thick silicon oxynitride formed on Si(100), the blocking capability of the silicon oxynitride against oxidation in dry-O2 anneal at 500°C has been studied as a function of nitrogen content in the barrier layer in the range within ∼11at.%. With increasing nitrogen content, the interfacial oxide thickness is decreased linearly and, to suppress the growth of the interfacial oxide layer within two monolayers, a nitrogen content of ∼10at.% is necessary. Observed efficient blocking against oxidation, even for the case with a nitrogen content as small as ∼6at.%, is attributable to the improved homogeneity in the Si-O-Si bonding features at the interface by nitrogen incorporation of a few at.%, which is suggested from the experimental fact that the bandwidth of LO phonons near the interface due to the nitrogen incorporation is decreased as obtained by FT-IR-ATR measurements.
Stability of Indium Tin Oxide/Polymer Interfaces
Authors: Crispin X. , Crispin A. , de M. P. , Marciniak S. , Osikowicz W. , Jönsson S. , Fahlman M. , Kugler Th. , van IJzendoorn L. J. , de M. J. A. , Salaneck W. R. 
Published: April 2011

ABSTRACTInterfacial chemistry at indium tin oxide/polymer interfaces is of fundamental importance for the performance of polymer-based light emitting diodes. X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry are used to investigate the stability of the interface formed between indium tin oxide and (i) the light emitting polymer poly(p-phenylenevinylene), and (ii) the hole injecting layer poly(3,4-ethylenedioxythiophene) polystyrenesulfonate. The formed interfaces are not stable and indium-containing species diffuse from the metal oxide surface into the polymer layers.
Role of Ambience on the Diffusion of Charge Carriers in the Tio2 Layers Investigated by the Photovoltage Technique
Authors: Duzhko V. , Rappich J. , Dittrich Th. 
Published: April 2011

ABSTRACTThe transition from anatase to rutile crystalline phase and from continuous to porous morphology was observed by Raman spectroscopy and scanning electron microscopy, respectively, in anodic TiO2 layers as the time of anodization was increased. The mechanism of the PV formation changes from trap- limited PV in thin continuous layers to diffusion PV in thick porous layers. The generation of excess charge carriers and their subsequent separation in space are strongly dependent on the ambience (air, vacuum, water) in porous layers. The importance of polar water molecules for screening of surface ions of porous TiO2 and excess charge carriers separated in space is discussed.
“Novel Mechanisms on the Growth Morphology of Films“
Authors: Lu T.-M. , Zhao Y.-P. , Drotar J.T. , Karabacak T. , Wang G.-C. 
Published: April 2011

ABSTRACTRandom surface roughness very often can occur during the growth or etching of films under non-equilibrium conditions. Several competing mechanisms such as noise, surface diffusion, and shadowing all play a role in the evolution of surface roughness. However, recent results obtained in many growth and etching processes exhibit an unusual tendency: the morphology is very rough where it is expected to be smooth and vice versa. The origin, we believe, is due to the fact that during the deposition and etching processes the atoms very often do not stick to the surface upon their first strikes. Atoms actually bounce around before all settle on surface sites. This non-unity sticking probability can lead to a very rough surface during etching and a very smooth surface during sputter or chemical vapor deposition that cannot be explained by the conventional mechanisms.
Kinetic Modeling Of Dopant And Impurity Surface Segregation During Vapor Phase Growth: Multiple Mechanism Approach
Authors: Arnold Craig B. , Aziz Michael J. 
Published: April 2011

ABSTRACTWe propose a new kinetic model for surface segregation during vapor phase growth that accounts for multiple segregation mechanisms, including mechanisms for terrace mediated exchange and step edge mediated exchange. The major result of the model is an analytic expression for the experimentally measured segregation length and profile broadening that can be readily calculated without the need for numerical simulations. We compare the model to experimental measurements for the temperature dependence of segregation of Sb in Si(001). The model is able to accurately describe both the anomalous segregation at low temperature and the transition between equilibrium and kinetically limited segregation at high temperature. An excellent agreement is obtained using realistic energies and pre-exponential factors for the kinetic rate constants. The model can be applied to other segregating systems in planar geometries, including metallic and III-V semiconducting thin films.
Threshold Energy for Generating Damage with Cluster Ion Irradiation
Authors: Seki Toshio , Aoki Takaaki , Nakai Atsuko , Matsuo Jiro , Takaoka Gikan H. 
Published: April 2011

ABSTRACTIn order to understand the damage formation by cluster ion irradiation, Si substrates were irradiated with Ar cluster ions at the acceleration energy of 1–20keV. The mean size of cluster was about 3000 atoms. The amount of damage after Ar cluster ion irradiation was measured with Rutherford backscattering spectrometry (RBS). The amount of damage was decreased with decrease of the energy and no damage formed at less than 2keV. This energy of 2keV represents the threshold energy to generate damage with the cluster size of 3000. According to Molecular dynamics (MD) simulation, the damage formation with cluster ion irradiation also depends on cluster size. The size dependence of amount of damage has been investigated experimentally. The cluster size distribution could be changed with the ionization condition and could be measured using Time-of-Flight (TOF) method. The threshold energy was increased with cluster size. These results indicate that undamaged films can be created by using large size of cluster ion with low acceleration energy.
The surfactant effects of antimony on the formation of InAsSb nanostructures on GaAs by metal-organic chemical vapor deposition
Authors: Cederberg J.G. , Biefeld R.M. 
Published: April 2011

ABSTRACTWe have investigated InAsSb nanostructures formed on GaAs during MOCVD. The transition thickness from 2D growth to 3D growth is reduced by the addition of TMSb/Sb4. This is consistent with both an increase in the adatom diffusion length and a reduction in the epilayer/vapor surface energy attributed TMSb/Sb4.
Biomedical Potential of a Zirconium-Based Bulk Metallic Glass
Authors: Horton J. A. , Parsell D. E. 
Published: April 2011

ABSTRACTDue to their unique mechanical properties, bulk metallic glasses (BMG) have potential for biomedical applications. Biocompatibility and corrosion tests of a zirconium-based BMG showed comparable behavior to current implant alloys. Mechanical properties, such as an elastic limit of 2% and a yield strength of 1700 MPa, are significantly higher than current implant alloys. In addition, it was found that medical MRI images of BMG, possibly due to the amorphous structure, are significantly better than other alloys even though the reference alloy contains 14.6 at.% Ni. Nickel-free compositions also retained similar glass forming characteristics and showed even better MRI images. Edge holding for cutting tool applications was demonstrated. Fatigue tests were performed in simulated body conditions and directly compared to Ti-6 Al-4 V. While one specimen failed at more than 3,000,000 cycles at 500 MPa, there was much scatter in the data. Further concentration on processing issues to produce pore free material is needed to produce reliable materialfor prototype development. Potential uses, especially associated with an interventional MRI for MRI guided surgeries, will be discussed.
Thermal Tempering of Bulk Metallic Glasses
Authors: Aydiner Cahit C. , Üstündag Ersan 
Published: April 2011

ABSTRACTThe recent development of multi-component alloys with exceptional glass forming ability has allowed the processing of large amorphous metal samples. The possibility of formation of thermal tempering stresses during the processing of these bulk metallic glass (BMG) specimens was investigated using the (1) instant freezing, and (2) viscoelastic models. Both models yielded similar results although from vastly different approaches. It was shown that fast convective cooling of Zr41.2Ti13.8Cu12.5Ni10Be22.5 plates could generate significant compressive stresses on the surfaces balanced with mid-plane tension. The crack compliance method was then employed to measure the stress profiles in a BMG plate that was cast in a copper mold. These profiles were roughly parabolic suggesting that thermal tempering was indeed the dominant residual stress generation mechanism. However, the magnitude of the measured stresses (with peak values of only about 1.5% of the yield strength) was significantly lower than the modeling predictions. Possible reasons for this discrepancy are described in relation to the actual casting process and material properties.
Effects of Annealing and Annealing with Pressure on Devitrification of Al87Ni7Gd6
Authors: Wesseling Paul , Ko B.C. , Vatamanu L.O. , Caris J. , Lewandowski J.J. 
Published: April 2011

ABSTRACTThe effects of annealing for 30 minutes at temperatures ranging from 123–232°C on the structure evolution, resulting hardness, and tensile properties were determined for amorphous ribbons of Al87Ni7Gd6. Structure evolution was determined using a combination of XRD, DSC, and TEM, while micro-hardness and tensile testing of ribbon specimens was used to evaluate the mechanical properties. Significant effects of annealing on the evolution of structure and properties were obtained, while the superposition of 940 MPa pressure during annealing further enhanced the structure evolution with corresponding changes to the resulting properties.
Ductile Dendritic Phase Reinforced Ti-Base Bulk Metallic Glass-Forming Alloys
Authors: He G. , Eckert J. , Löser W. , Schultz L. 
Published: April 2011

ABSTRACTBulk metallic glasses (BMG) exhibit high strength but limited ductility due to their inhomogeneous deformation behavior under load, which seriously limits their application. To prevent the inhomogeneous deformation, attempts have been made by introducing in situ formed ductile dendritic phases in present study. Ti-base BMG-forming alloys were selected and modified by adding refractory metals Nb, Ta, Mo and Zr. Ductile dendrites / nanostructured matrix composites were synthesized which exhibit a plastic strain larger than 14% together with high strength (ultimate strength higher than 2400 MPa). The experimental results show evidence that shear banding is the main deformation mode in nanostructured matrix. The localized shear bands are limited in the inter-dendrite regions by micrometer-sized dendrites. The dendrites act as obstacles to limit the excessive deformation in the localized shear bands and contribute to the plasticity by dislocations.
Glass Formation and Reddish Coloring Properties in Zinc Phosphotellurite Glass.
Authors: Konishi Tomoya , Hondo Takaharu , Araki Tetsuo , Nishio Keishi , Tsuchiya Toshio , Matsumoto Takehisa , Suehara Shigeru , Todoroki Shin-ichi , Inoue Satoru 
Published: April 2011

ABSTRACTVarious compositions of P2O5-TeO2-ZnO glasses were prepared by using a combinatorial glass preparation system including a batch-preparing apparatus and a multi-sample casting machine, and the compositional dependence of glass forming tendency and thermal properties were intensively investigated. The samples exhibited a variety of colors, such as transparent, yellow, wine red and brown depending on its composition. Analyses with scanning electron microscopy and X-ray photoelectron spectroscopy revealed that the reddish coloration is responsible for colloidal suspension of nanometer sized elemental Te particles.
Computer-Aided Development of Multicomponent Metallic Glasses
Authors: Takeuchi Akira , Inoue Akihisa 
Published: April 2011

ABSTRACTAsynthesized calculation model for developing metallic glasses has been created by taking into account criteria for the achievement of high glass-forming ability (GFA) and viscosity. The model deals with amorphous-forming composition region (AFCR), crystallization temperature (Tx) and three GFA factors: critical cooling rate (Rc), reduced glass-transition temperature (Tg/Tm) and supercooled liquid region (ΔTx=Tx-Tg) where Tg and Tm are glass transition and melting temperature, respectively. The principle of the model is based on thermodynamic functions for multicomponent systems, i.e., mismatch entropy and mixing enthalpy which express the criteria in terms of the number of elements, atomic size differences and the heat of mixing. By combining these thermodynamic quantities with the Miedema's semi-empirical model, AFCR was calculated, and was compared with the experimental results. The GFA factors were also analyzed from viscosity. The Rc was derived from transformation diagram of metallic glasses for crystallization while ΔTx was calculated by solving a differential equation expressing the change in free volume with temperature. As a result of these analyses, Rc-Tg/Tm and R-ΔTx diagrams were found to fit with the experimental results qualitatively. Furthermore, crystallization temperature (Tx) was also calculated for multicomponent metallic glasses by the modification of the Miedema's binary model for the calculation of Tx. The reduced crystallization temperature (Tx/Tl), where Tl is liquidus temperature, was calculated for evaluating GFA of metallic glasses instead of Tg/Tm. Some of the calculation methods used in the present study have theadvantage giving results as a function of composition; thus, there exists possibility to lead to the prediction of glassy alloys compositions. In this sense, the present calculation methods are completely different to the current method for the development of new metallic glasses relying on the empirical criteria which suggest only appropriate systems and/or elements of the alloysfor the achievement of high GFA. In near future, this kind of calculation technique can be used for the prediction of optimal compositions of the metallic glasses with high GFA.