bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dilute Group III-AsN: Bonding of Nitrogen in GaInAsN and AlGaAsN on GaAs and Realization of Long Wavelength (2.3 μm) GaInAsN QWs on InP
Authors: Serries D. , Geppert T. , Köhler K. , Ganser P. , Wagner J. 
Published: April 2011

ABSTRACTRecent results on the local bonding of nitrogen in dilute GaInAsN and AlGaAsN on GaAs are reviewed, revealing that bonding of nitrogen in GaInAsN is controlled by an interplay between bond cohesive energy and reduction of local strain. Thus, III-N bonding in GaInAsN can be changed from Ga-N to In-N by post-growth thermal annealing. In AlGaAsN, in contrast, nitrogen bonds preferentially to Al, i.e. Al-N bonds are formed, due to the much larger cohesive energy of the Al-N bond. Further, results on indium-rich highly strained GaInAsN quantum wells on InP substrate are reported, showing room-temperature photoluminescence at wavelengths up to 2.3 μm. This result demonstrates the potential of high indium content dilute GaInAsN for InP-based long wavelength diode lasers.
Composition of β-FeSi2 Thin-Films Grown by a Pulsed Laser Deposition Method
Authors: Uekusa Shin-ichiro , Yamamoto Masahiro , Tsuchiya Keiichi , Miura Noboru 
Published: April 2011

ABSTRACTWe prepared othorhombic β-FeSi2 thin-films on Si(111) substrates by a pulsed laser deposition method (PLD) and studied the relationship between bandgap energy and composition ratio by themal annealing of β-FeSi2 thin-films on Si substrate. When the substrate temperature was 500·°C, β-FeSi2 thin-films were grown on Si(111) substrates. The sample prepared on Si(111) substrate was a monocrystalline structure since only (220) or (202) signals of β-FeSi2 were observed. A large amount of defects existed in the thin film. These defects were reduced by using high temperature and long time annealing. Heat treatment of 20 hours or more time was effective for reducing diffect. The iron diffusion of β-FeSi2/Si interface was observed by RBS spectra. Composition ratio of the prepared β-FeSi2 was Fe:Si=30:70. As-deposition β-FeSi2 was Si-rich. The p-n diode characteristics of these heterostructure diodes were investigated by C-V measurements. β-FeSi2/Si interface prepared by 400· °C was an ideal one-side step junction. The surface roughness was decreased by annealing.
Characterization of Metallic and Metal Oxide Nanoparticles Produced by Electrothermal-Chemical Synthesis
Authors: Schroder Kurt A. , Wilson Dennis E. , Kim Kyoungjin , Elliott Henry E. 
Published: April 2011

ABSTRACTElectrothermal-Chemical Synthesis (ETCS) is a relatively new process for the synthesis of nanocrystalline powders. With ETCS nanoparticles are formed through the controlled chemical reaction of a metal plasma, produced by cathode erosion, with a gas. By controlling the quench rate of the plasma precisely, the average particle size can be varied from as small as 6–8 nm up to 100 nm and above. The process is quite versatile and can be used to produce a wide variety of nanopowders including metals, oxides, and nitrides. However, before the nanoparticles produced by this process (or any other process for that matter) can find wide scale commercial acceptance, their physical properties must be characterized. Among many characterization techniques, electron microscopy can provide structural, chemical, and morphological information on nanoparticles. In this paper, we will discuss the SEM and TEM characterization of metal and metal oxide nanoparticles powders produced by ETCS.
Yellow-green emission for ETS-LEDs and lasers based on a strained–InGaP quantum well heterostructure grown on a transparent, compositionally graded AlInGaP buffer
Authors: McGill Lisa , Wu Juwell , Fitzgerald Eugene 
Published: April 2011

ABSTRACTEpitaxial-transparent-substrate light emitting diodes with a primary emission peak at 590nm and a secondary peak at 560nm have been fabricated in the indium aluminum gallium phosphide (InAlGaP) system. The active layer consists of an undoped, compressively strained indium gallium phosphide (InGaP) quantum well on a transparent In0.22(Al0.2Ga0.8)0.78P/ ∇x[1nx(Al0.2Ga0.8)1-xP] /GaP virtual substrate. Theoretical modeling of this structure predicts an accessible wavelength range of approximately 540nm to 590nm (green to amber). Emission with a peak wavelength of 570nm has been observed via cathodoluminescence studies of undoped structures with a quantum well composition of In0.35Ga0.65P. Light emitting diodes have been fabricated utilizing simple top and bottom contacts. The highest LED power of 0.18μW per facet at 20mA was observed for a quantum well composition of In0.32Ga0.68P and a bulk threading dislocation density on the order of 7×106 cm-2. The spectrum of this device was composed of two peaks: a weak peak at the predicted 560nm wavelength and a stronger peak at 590nm. Based upon superspots present in electron diffraction from the quantum well region, we believe that the observed spectrum is the result of emission from ordered and disordered domains in the active region. The same device structure grown with a bulk threading dislocation density on the order of 5×107 cm-2 exhibited an identical spectral shape with a reduced power of 0.08μW per facet at 20mA. For a quantum well composition of In0.37Ga0.63P and an overall threading dislocation density on the order of 5×107 cm-2, a single peak wavelength of 588nm with a power of 0.06μW per facet at 20mA was observed.
Lanthanide Doped Cubic Boron Nitride
Authors: Vetter U. , Taniguchi T. , Wahl U. , Correia J. , Müller A. , Ronning C. , Hofsäss H. , Dietrich M. , Collaboration Isolde 
Published: April 2011

ABSTRACTFirst basic investigations on lanthanide implanted cubic boron nitride were performed with focus on the site of the implanted ions as well as their luminescence behaviour. In order to investigate the lattice sites of lanthanides in c-BN, we implanted single crystal c-BN with radioactive 139Ce ions using the on-line isotope separator ISOLDE at CERN. After the samples were annealed at 1193 K, direct lattice location studies were performed using the conversion electron emission channeling technique and showed a near-substitutional fraction of the implanted ions of at least 10 %. Additionally, poly crystalline c-BN samples were implanted with stable Eu and Tm ions in order to investigate the luminescence properties of triply ionised lanthanides in the c-BN host. It is found that the annealing of the implanted samples at high temperature and high pressure results in strong luminescence of the Eu3+ ions in the orange and moderate luminescence of the Tm3+ ions in the blue. In case of the Eu implanted samples, the luminescence is assigned to the 5D0-7FJ intra-4f electron transitions of Eu3+, in case of the Tm implanted samples, detectable transitions are 1D2-3H6, 1D2-3F4, 1G4-3H6. of Tm3+.
Growth and characterization of epitaxial films of ZnGeP2.
Authors: Verozubova G.A. , Gribenyukov A. I. , Ohmer M.C. , Fernelius N.C. , Goldstein J.T. 
Published: April 2011

ABSTRACTThermodynamic analysis of the vapor phase over ZnGeP2 in Zn-Ge-P-Cl system has been carried out. The analysis showed that this system can be used for the vapor growth of ZnGeP2. Homoepitaxial layers of ZnGeP2 were grown in a closed system using chemical vapor transport. Electrical and photoluminescence properties of the layers were studied, and crystal lattice parameters were measured. Comparison of properties for bulk and vapor grown ZnGeP2 crystals were carried out. It was found that the vapor grown crystals have more perfect structure than the bulk ones, particularly, they have significantly lower vacancy concentration.
Domain Wall Magnetoresistance and Complex magnetic Response in Antiferromagnetically Coupled Fe/Cr Multilayers
Authors: Aliev F. G. , Villar R. , Schad R. , Martinez J. L. 
Published: April 2011

ABSTRACTFor antiferromagnetically coupled Fe/Cr(100) multilayers the low field contribution to the resistivity, which is caused by the domain walls (DWs), is strongly enhanced at low temperatures. The low temperature resistivity increases approximately according to a power law with the exponent 0.7–1. This behaviour can be explained by the suppression of anti-localization effects by the nonuniform gauge fields caused by the domain walls. Analyses of complex low frequency magnetic susceptibility shows an enhancement of the magnetic losses at low magnetic fields, which may be related to the AC field induced DWs movement. At low temperatures (T<100K) DWs become pinned. For frequencies (102<f< 103) Hz at temperatures below 10K, this hysteretic low field peak in the magnetic losses transforms to a non-hysteretic dip for |H|< 20 Oe, indicating a possible qualitative change in the dynamics of the DWs. The frequency dependence of the dissipation at 2K, may be reasonably well fitted by the expression that describes the losses of a damped oscillator with a single relaxation time of about 10-4 sec.
Ab initio study of CPP transport in Fe/Cr/Fe trilayers: influence of transition metal impurities
Authors: Herper Heike C. , Entel Peter , Szunyogh Laszlo , Weinberger Peter 
Published: April 2011

ABSTRACTThe transport properties of Fe(001)/Cr/Fe(001) trilayers are discussed with respect to the influence of transition metal impurities in form of layers. We are able to show that the periodicity of the giant magnetoresistance is directly influenced by the interlayer exchange coupling (IEC). Furthermore, it is observed that the behavior of the IEC strongly depends on whether an impurity overlayer of Mn or V is used. It turns out that the size of the GMR is only little effected by 3d-transition metal impurities, which is in agreement with the experimental findings. The electronic and magnetic properties of the trilayers have been investigated within the fully relativistic, spin-polarized SKKR method and the LDA. The transport properties of the Fe/Cr/Fe systems have been derived from the fully relativistic spin-polarized Kubo-Greenwood equation.
In-Plane Transport of Doped Manganite Trilayers
Authors: Alldredge Lisa Berndt , Suzuki Y. 
Published: April 2011

ABSTRACTWe have synthesized and characterized doped manganite trilayers composed of La0.7Sr0.3MnO3 (LSMO) and La0.7Ca0.3MnO3 (LCMO). Because of the isostructural nature of the Sr and Ca doped manganites, trilayers exhibit good epitaxy as observed in X-ray diffraction. Magnetization measurements reveal magnetization values consistent with bulk values. In-plane transport of these trilayers reveals anisotropic magnetoresistance and high field negative magnetoresistance attributed to the suppression of spin fluctuations at high fields.
Electro-structural and Film Growth Properties of Room-temperature Deposited Indium-Tin-Oxide on Polymer Substrates
Authors: Park Sung Kyu , Han Jeong In , Moon Dae Gyu , Kim Won Keun , Kwak Min Gi 
Published: April 2011

ABSTRACTElectrical and structural properties of indium-tin-oxide (ITO) films on flexible polymer substrates were investigated. Room temperature sputtered ITO films on polymer substrates are initially amorphous but become partially crystalline as oxygen partial pressure decreases under 1.5%. The crystallinity shows more (400) and (222) preferentially oriented textures as decreasing of oxygen pressure resulting in lower resistivity. Moreover, an interesting growth property similar to 3D growth mechanism including larger grain size and columnar-like grain structure was also observed. It is considered that the columnar-like grain structure is probably attributed to the poor surface morphology of polymer substrates Based on the experiments, we obtained high performance ITO films on a polycarbonate substrate including 3.8 × 10 –4 Ω-cm in resistivity and transmittance above 80% in the visible ranges at 0.2% oxygen partial pressure.
Reactive Solid-Phase Epitaxy: ∼ A novel growth method for single-crystalline thin films of complex oxides with superlattice structure ∼
Authors: Ohta H. , Nomura K. , Hiramatsu H. , Suzuki T. , Ueda K. , Orita M. , Hirano M. , Ikuhara Y. , Hosono H. 
Published: April 2011

ABSTRACTWe have developed a novel growth method for single-crystalline film of natural superlattice oxides and named the method “Reactive Solid-Phase Epitaxy (R-SPE).” Single-crystalline thin films of homologous series In-GaO3(ZnO)m (m=integer) are fabricated by the R-SPE method and its growth mechanism, especially a role of ZnO epitaxial layer, is clarified. High-temperature annealing of bi-layer films consisting of an amorphous InGaO3(ZnO)5 layer deposited at room temperature and an epitaxial ZnO layer on YSZ substrate allows for the growth of single-crystalline film with a controlled chemical composition. The ZnO layer plays an essential role in determining the crystallographic orientation, while the thickness ratio between the two layers controls the film composition.
The Interactions between SBT and Transition Metal Studied by DV-Xa Method
Authors: Liu Hanxing , Min Xinmin , Sun Xiaoqin , Xiao Jing , Ouyang Shixi 
Published: April 2011

ABSTRACTIn the present study electronic structures of the interface between SBT and transition metal including Au, Ag, Cu, Ni, Pt were studied by employing DV-Xα method. The calculations were performed on cluster models of the interface which were SrTa8O36-M2 (M=Au, Ag, Cu, Ni, Pt, and Bi). The calculations results including Fermi level, bond order, atomic charge distribution shown that there existed significant hybridization between metal d states and the O2p–Ta3d states. The Fermi levels of the metals located in the gap of SBT and metal-induced states, and the position of the Fermi levels did not change greatly due to the different transition metals. The charge of Sr and the transition metal atom transferred to oxygen atom, so that the bonding between Sr (or metal atom) and O was almost ionic bonding. The interactions between transition metal and SBT mainly came from the Coulomb interaction.
A Comparison of Tunneling Through Thin Oxide Layers on Step-free and Normal Si Surfaces
Authors: Oliver Antonio C. , Blakely Jack M. 
Published: April 2011

ABSTRACTSurface and interface morphology may play an important role in the electrical performance of metal-oxide-semiconductor (MOS) devices with small characteristic dimensions. In previous work we showed how steps on the silicon surface influence the Si-SiO2 interface morphology and the outer oxide surface morphology following thermal oxidation [1]. The Si-SiO2 interface morphology is largely determined by the starting silicon substrate step distribution and atomic steps at the Si surface cause an inherent variation in oxide thickness after thermal oxidation. In the present study we report how roughness caused by increased interfacial step density may affect the electronic tunneling characteristics of an MOS device structure. To determine the extent to which the step morphology plays a role in the tunneling behavior of such devices, similar arrays of capacitors were fabricated on both Si surfaces with reduced step density and surfaces which had not undergone any special surface step removal treatment. The leakage currents due to tunneling for the two types of capacitors were measured and compared. Atomic steps cause an effective decrease in oxide thickness in those capacitors without reduced step density and this leads to increased leakage current.
A Structural Study of the Amorphous to Crystalline Transformation in In2O3 Thin Films
Authors: Yaglioglu Burag , Yeom Hyo-Young , Chason Eric , Paine David C. 
Published: April 2011

ABSTRACTWe have investigated the structure of sputter deposited amorphous and crystalline indium oxide films by electron diffraction. Selected area diffraction patterns were recorded for both states from which radial density functions were derived. The comparison of the crystalline radial density function to the amorphous one shows that the first nearest neighbor distance corresponding to the In-O bond length is 2.2Å and is the same for both states. A model density function for crystalline structure was used to explore the difference in higher order peak positions. We report that the In-In separation in amorphous state has a single characteristic distance of 3.6Å compared to the crystalline state which has two non-equivalent In sites and consequently different separations as In(1)-In(2) at 3.4Å and In(2)-In(2) at 4.3Å.
Heteroepitaxial Growth of a Wide Gap P-type Oxysulfide, LaCuOS
Authors: Hiramatsu Hidenori , Ueda Kazushige , Ohta Hiromichi , Hirano Masahiro , Hosono Hideo 
Published: April 2011

ABSTRACTEpitaxial films of LaCuOS, a wide gap p-type semiconductor, were grown on yittria- stabi-lized-zirconia (YSZ) (001) or MgO (001) substrates by a reactive solid phase epitaxy (R-SPE) method. Crystal quality, electrical and optical properties on the epitaxial films on each substrate are examined in this paper. Achievement of the heteroepitaxial growth of LaCuOS on the MgO (001) substrate improves optical properties of LaCuOS such as spectral bandwidths and emission intensity, suggesting that the MgO (001) substrate is more preferable than the YSZ (001) for epitaxial growth substrate for LaCuOS.
Comparison of Growth Morphology in Ge (001) Homoepitaxy Using Pulsed Laser Deposition and MBE
Authors: Leonard John P. , Shin Byungha , McCamy James W. , Aziz Michael J. 
Published: April 2011

ABSTRACTDifferences in the homoepitaxy of Ge(001) are explored using a dual MBE/PLD deposition system. With identical substrate preparation, temperature calibration, background pressure and analysis, the system provides a unique comparison of the processes arising only from kinetic differences in the flux and at the surface. All films show mounded growth. At substrate temperatures below 200°C, PLD films are smoother than MBE films, whereas they are similar at higher temperatures.
X-Ray Characterization of Nanostructured Semiconductor Short-Period Superlattices
Authors: Li Jianhua , Moss S. C. , Holy V. , Norman A.G. , Mascarenhas A. , Reno J.L. 
Published: April 2011

ABSTRACTSpontaneous lateral composition modulation during semiconductor thin film growth offers a particularly versatile and cost-effective approach to manufacture nanoscale devices. Recent experimental and theoretical studies have revealed that regular lateral composition modulation can be achieved via MBE growth of the so-called short-period superlattices and can be optimized via appropriate control of the global strain, substrate surface, and processing conditions. To characterize this phenomenon, we used synchrotron x-ray scattering to identify the interfacial morphology and laterally modulated composition profile of nearly strain-balanced InAs/AlAs short-period superlattices. Our results were compared with a theoretical model. It is shown that the lateral composition modulation is predominately caused by a vertically correlated morphlogical undulation of the superlattice layers.
Motions of Si(100) Steps at Low Temperature. A Study by Molecular Dynamics
Authors: Mazzone A.M. 
Published: April 2011

ABSTRACTAn isothermal Molecular Dynamics simulation method has been applied to the study of motions of steps on Si(100). The steps have a monolayer height and their temperature is below the roughening transition (i.e. T≤ 1000K). The calculations predict spontaneous motions even in this low temperature range and describe the functional dependence of the displacements of step-edge atoms on the step geometry, size and temperature and on the nature of the interatomic forces. Owing to the use of the Fourier analysis, these results can be applied to structures of realistic size by a proper scaling of the wavevectors.
Time Evolution of the Microstructure of VO2(B) Films Deposited on Glass by MOCVD
Authors: Sahana M. B. , Subbanna G. N. , Shivashankar S. A. 
Published: April 2011

ABSTRACTThin films of VO2(B), a metastable polymorph of vanadium dioxide, have been grown on glass by low-pressure metalorganic chemical vapor deposition (MOCVD). The films grown for 90 minutes have atypical microstructure, comprising micrometer-sized, island-like entities made up of numerous small, single-crystalline platelets (≅1 μm) emerging orthogonally from larger ones at the center. Microstructure evolution as a function of deposition time has been examined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The metastable VO2(B) transforms to the stable rutile (R) phase at 550°C in inert ambient, which on cooling convert reversibly to M phase. Electron microscopy shows that annealing leads to the disintegration of the VO2(B) platelets into small crystallites of the rutile phase VO2(R), although the platelet morphology is retained. The magnitude of the jump in resistance at the semiconductor-to-metal, VO2(M)→VO2(R) phase transition depends on the arrangement of polycrystalline platelets in the films.
Characterization of Eu- and Y-polytantalate Films Deposited by RF Diode Sputtering
Authors: Vasilyev Vladimir S. , Drehman Alvin J. , Bouthillette Lionel O. 
Published: April 2011

ABSTRACTUsing radio frequency (RF) diode sputtering of sintered stoichiometric (Eu,Y)2O3:7Ta2O5 ceramic targets, thin films (0.2–0.6 m) of Eu- and Y-polytantalates, and their solid solution EuxY1-xTa7O19 were deposited on fused silica, Si (100) and sapphire (001) substrates under various sputtering conditions. As-grown films were amorphous, and were crystallized by post-annealing in oxygen at 900 to 1000 °C. The influences of deposition gases (Ar and O2-partial pressure) substrate material, deposition time, substrate temperature, and post-annealing time and temperature on the structural, morphological and photo-luminescence (PL) properties of Eu 3+-ions in the films have been studied and compared to properties of sintered (Eu,Y)Ta7O19 ceramic and EuTa7O19 single crystals.
Crystal Phases of Glass-Forming Mixtures
Authors: Fernández Julián R. , Harrowell Peter 
Published: April 2011

ABSTRACTWe compare the potential energy at zero temperature of a range of crystal structures for a glass-forming binary mixture of Lennard-Jones particles. The lowest energy ordered state consists of coexisting phases of a single component face centered cubic structure and an equimolar cesium chloride structure. An infinite number of layered crystal structures are identified with energies close to this groundstate. We demonstrate that the finite size increase of the energy of the coexisting crystal with incoherent interfaces is sufficient to destabilize this ordered phase in simulations of typical size. Specific local coordination structures are identified as of possible structural significance in the amorphous state. We observe rapid crystal growth in mixtures near the equimolar composition.
Nanocrystalline ZrN particles embedded in Zr-Fe-Cu-Al-Ni amorphous matrix.
Authors: Bab Marisa A. , Damonte Laura C. , Mendoza-Zélis Luis , Deledda Stefano , Eckert Jurgen 
Published: April 2011

ABSTRACTMelt-spun Zr64Al7Cu17Ni10Fe2 amorphous ribbons were milled under nitrogen atmosphere for different times. The resulting nitrided powders were studied by x-ray diffraction, Mössbauer spectroscopy and differential scanning calorimetry. The formation of nanosized crystalline particles, with cubic δ-ZrN structure, dispersed in the amorphous matrix was observed along with a change in the composition of the amorphous phase. Prolonged milling leads to the additional precipitation of late transition metals (Fe,Ni,Cu). The nitride particles affect the crystallization behavior and modify the thermal stability of the amorphous alloy.