bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence for localization effects in GaAsSb/InP heterostructures from optical spectroscopy
Authors: Chouaib Houssam , Bru-Chevallier Catherine , Benyattou Taha , Lahreche Hacene , Bove Philippe 
Published: April 2011

ABSTRACTGaAsSb is a promising material for the base of a new generation of Heterojunction Bipolar Transistors (HBT) on InP, as it is expected to allow the elaboration of high-speed digital circuits (80 to 100 Gbits/s). Emitter-base interfaces between GaAsSb and InP need to be well controlled to ensure good performance of the HBT, and this requires a careful analysis of both material and interface quality. Photoluminescence (PL) experiments as a function of temperature and of power excitation density, as well as photoreflectance (PR) measurements are performed on GaAsSb/InP heterostructures in order to get information about ordering and segregation effects in antimonide alloys.From the PL recombination energy across the type II interface and at the GaAsSb band-edge, the band offset ΔEC between InP and GaAsSb is calculated. The evolution of the band to band PL recombination is studied as a function of temperature: the energy and intensity of the type I PL transition are shown to exhibit specific behaviors, which are typical of carrier localization effects in semiconductor alloys. At low temperature, the shape of the PR spectrum results in an atypical steplike background, which is analyzed as a band filling effect in consequence of the carrier localization on potential fluctuations.
CdZnSe/Zn(Be)Se Quantum Dot Structures: Size, Chemical Composition and Phonons
Authors: Gu Y. , Kuskovsky Igor L. , Fung J. , Robinson R. , Herman I. P. , Neumark G. F. , Zhou X. , Guo S. P. , Tamargo M. C. 
Published: April 2011

ABSTRACTThe size and chemical composition of optically active CdZnSe/ZnSe and CdZnSe/Zn0.97Be0.03Se quantum dots (QDs) are determined using photoluminescence, photoluminescence excitation and polarized Raman scattering spectroscopies. We show that the addition of Be into the barrier enhances the Cd composition and the quantum size effect of optically active QDs. Additionally, surface phonons from QDs are observed in CdZnSe/ZnBeSe nanostructures.
Characterization of Uranium Particles Produced via Pulsed Laser Deposition
Authors: Glade S. C. , Trelenberg T. W. , Tobin J. G. , Hamza A. V. 
Published: April 2011

ABSTRACTWe have constructed an experimental apparatus for the synthesis (via pulsed laser deposition) and analysis of nanoparticles and thin films of plutonium and other actinides. In-situ analysis techniques include x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS). Also, the oxidation kinetics and the reaction kinetics of actinides with other gaseous species can be studied with this experimental apparatus. Preliminary results on depleted uranium are presented.
Quasicrystal approximants with novel compositions and structures
Authors: Mihalkovič M. , Widom M. 
Published: April 2011

ABSTRACTWe identify several new quasicrystal approximants in alloy systems in which quasicrystals have not been previously reported. Some occur in alloys with large size contrast between the constituent elements, either containing small Boron atoms, or large Ca/Eu atoms, leading to quasicrystal structures quite different from currently known systems where the size contrast is smaller. Another group of the approximants are layered Frank-Kasper structures, demonstrating competition between decagonal and dodecagonal ordering within this family of structures.
Phononic Quasicrystals
Authors: Sutter Daniel , Krauss Günter , Steurer Walter 
Published: April 2011

ABSTRACTPhononic crystals are to sound what photonic crystals are to light and crystals are to electrons. If the wavelength is of the same order of magnitude as the typical distances between the objects in their ordered arrangement, then the interaction is dominated by diffraction besides refraction. Depending on the spectral properties of the material, band gaps appear for certain frequencies. In special cases, these gaps are omni-directional. A huge amount of application-driven research has been performed on photonic crystals, much less on phononic crystals, and almost nothing on phononic quasicrystals. We present here the first experimental studies on two-dimensional, quasiperiodic, phononic crystals. Our experiments have been performed with ultrasound on phononic crystals and quasicrystals consisting of steel cylinders in water. The pros and cons of phononic quasicrystals are discussed.
Quasicrystal Formation in a Zr-based Bulk Metallic Glass
Authors: Liu L. , Chan K. C. , Pang G. K. H. 
Published: April 2011

ABSTRACTZr65Ni10Cu7.5Al7.5Ag10 bulk metallic glass with a diameter of 2 mm and a length of 50 mm was prepared by copper-mould casting. The metallic glass obtained follows two-step crystallization reactions with the initial formation of metastable quasicrystals from amorphous phase, followed by the formation of a stable intermetallic Zr2Cu from the post-formed quasicrystals. In this paper, the microprocess of the amorphous-to-quasicrystalline transformation of Zr65Ni10Cu7.5Al7.5Ag10 bulk metallic glass was studied in detail by TEM and high resolution TEM coupled with nanobeam EDX. It was found that the amorphous-to-quasicrystalline transformation in the present system does not follow the traditional nucleation/growth mechanism. Instead, it undergoes a series of inter-processes and follows the sequence of phase transformation of amorphous → FCC Zr2Ni → Tetragonal Zr2Ni → Quasicrystals. Nanobeam EDX revealed that atomic diffusion was involved in all inter-processes of the phase transformations, suggesting that the amorphous-to-quasicrystalline transformation in the present bulk metallic glass is a non-polymorphous reaction.
Mechanical Spectroscopy of the Formation of Quasicrystalline Order in Rapidly Quenched Ti- and Zr-based Alloys
Authors: Sinning Hans-Rainer , Golovin Igor S. , Jianu Adrian 
Published: April 2011

ABSTRACTThe development of quasicrystalline (qc) order from different initial states (amorphous, nano- or poly-qc) was studied in rapidly quenched Ti-Zr-Ni(-Ag), Ti-Zr-Fe, and Zr-Cu-Ni-Al alloys by means of mechanical spectroscopy (vibrating-reed technique), including both the irreversible changes of Young's modulus and the Snoek-type relaxation peak of absorbed hydrogen as a probe, which are obviously sensitive to quite different types of ordering processes. The strongest annealing effects on Young's modulus were found for extreme nano-qc material at the amorphous limit, whereas order-induced narrowing of the hydrogen peak occurs only at comparatively larger grain sizes. More important differences in the properties of the hydrogen peak are found between quasicrystals of different compositions. The results are briefly discussed with respect to their implications for the amorphous-to-quasicrystalline transition and for the experimental distinction between different types of icosahedral quasicrystalline order.
Oxidation of amorphous Zr70Pd30 and coarse crystalline Zr2Pd
Authors: Jastrow Lioba , Köster Uwe 
Published: April 2011

ABSTRACTZr-based bulk metallic glasses are of increasing interest due to their excellent properties, e.g. high elastic limit or catalytic activity. For some applications (golf clubs, hydrogen storage) a good oxidation resistance is necessary; in other cases (catalysis) fast oxidation is required.Zr-Pd melt-spun glasses are known to exhibit “catastrophic” oxidation even at temperatures far below their glass transition. However, the surface of as-cast amorphous Zr70Pd30 was found to be protected by a thin native ZrO2 layer, thus allowing only localized nucleation of the oxidation reaction at preferred nucleation sites activated by destruction of the native oxide layer.Detailed cross-sectional SEM and TEM revealed a rather complicated microstructure of the oxide islands consisting of a lamellar structure of tetragonal and moniclinic ZrO2 with different Pd contents and embedded nanocrystalline Pd. There is also evidence for a Pd enriched reaction zone between the oxide cone and the glassy matrix.In order to understand the influence of the structure on the oxidation, the behavior of the metallic glass was compared with that of a crystallized alloy or even coarse crystalline Zr2Pd. Coarse crystalline Zr2Pd was found to be rather stable against oxidation, but exhibit very fast oxygen diffusion along the grain boundaries followed by oxide formation deep inside the material. Grain boundaries in the crystallized Zr70Pd30 does not exhibit such a behavior.
Shear thinning of the bulk metallic glass forming alloy Zr41.2 Ti13.8 Cu12.5 Ni10.0 Be22.5 close to the liquidus temperature.
Authors: Shaw Tyler , Way Christopher , Busch Ralf 
Published: April 2011

ABSTRACTThe viscous properties of the multi component Zr41.2 Ti13.8 Cu12.5 Ni10.0 Be22.5 bulk metallic glass forming alloy was studied above the liquidus temperature. A shear thinning behavior for the molten alloy has been discovered. The shear thinning behavior can be characterized as a power law fluid with a power-law index of -0.5. Additionally, at low shear rates and temperatures near the liquidus temperature a visco-elastic type response in the flow behavior is observed.
SiGe HBT/BiCMOS Technologies and their Applications to Communication ICs/LSIs
Authors: Oda Katsuya , Washio Katsuyoshi , Hashimoto Takashi 
Published: April 2011

ABSTRACTSelf-aligned ultra-high-speed SiGe HBTs were developed by using selective epitaxial growth (SEG) technology. The use of HCl-free SEG, incorporation of C, and optimization of doping profiles significantly improves the performance of the HBT, producing a transistor with a high cutoff frequency of 170 GHz and a maximum oscillation frequency of 204 GHz, for a minimum ECL gate delay time of 4.8 ps. This is applied in a 16:1 MUX with a maximum clock rate of 57 GHz. A 0.13-μm SiGe BiCMOS technology is also realized without any degradation of CMOS due to the high stability of SiGe HBTs. Furthermore, the structure of SiGe HBT is optimized for an emitter scaled down towards 100 nm, mainly through the use of a funnel-shaped emitter electrode to reduce both emitter and base resistances. High-speed operation of a static frequency divider demonstrates the advantage of SiGe HBTs for ultra-high-speed communications systems.
Heteroepitaxial growth and characterization of Ge and SiXGe1−X films on patterned silicon structures
Authors: Vanamu Ganesh , Datye Abhaya K. , Zaidi Saleem H. 
Published: April 2011

ABSTRACTWe describe novel 2-D structures that facilitate strain relief and allow us to obtain Ge epilayers that are free of defects. These structures can potentially absorb thermal expansion and lattice expansion mismatch as well as enable liftoff of heteroepitaxial layers for subsequent wafer reuse. Conventional lithography techniques were combined with reactive ion and wet-chemical etching to fabricate 2-D patterns of silicon posts. The dimensions of the posts were varied keeping the pitch (center to center distance) constant. Heteroepitaxial growth of Ge/SixGe1−x on these micrometer-scale structures was investigated. While, keeping the growth parameters constant, the geometry of the structures was varied to determine the optimum configuration for the highest quality heteroepitaxial growth. The quality of the Si1−xGex buffer system was investigated using high-resolution x-ray diffraction. Transmission electron microscopy (TEM) was used to analyze the epilayer cross-sections. Surface morphology was analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM) and optical microscopy. Our results show that the quality of the heteroepitaxial layers improves as the width of the posts in the 2-D pattern was decreased.
Arsenic diffusion in Si and Si0.9Ge0.1 alloys: Effect of defect injection
Authors: Uppal Suresh , Bonar J. M. , Zhang Jing , Willoughby A. F. W. 
Published: April 2011

ABSTRACTResults of intrinsic As diffusion in Si as well as in strained and relaxed Si0.9Ge0.1 layers are presented. Using Molecular Beam Epitaxy in-situ As doped epitaxial Si and compressively strained and relaxed Si-Ge layers were grown on Si substrates. The samples were annealed using Rapid Thermal Annealing (RTA) at 1000 °C. Arsenic diffusion is seen to be enhanced in SiGe than in Si. The enhancement factor is calculated to be 2.3 and 1.3 for relaxed and strained Si0.9Ge0.1, respectively. Also, using RTA in oxygen atmosphere, interstitial and vacancies were selectively injected in to the sample structures. Diffusion enhancement is also recorded in Si and Si-Ge structures with interstitial as well as vacancy injections over inert anneal. The results suggest that both interstitial and vacancy defects contribute to As diffusion in Si and Si0.9Ge0.1.
Ion Implantation and 1 MeV Electron Irradiation of 4H-SiC---Comparison Studies
Authors: Evwaraye A. O. , Smith S. R. , Mitchel W. C. , Farlow G. C. , Capano M. A. 
Published: April 2011

AbstractArgon ions (Ar+) were implanted into n-type 4H-SiC epitaxial layers at 600 °C. The energy of the ions was 160 keV and at a dose of 2 × 1016 cm−2. After post-implantation annealing at 1600 °C, Schottky diodes were fabricated on the ion implanted samples. Bulk n-type 4H-SiC samples were irradiated at room temperature with 1 MeV electrons at doses of 1 × 1016 to 5.1 × 1017 el/cm2. The current density of the beam was 0.91 μA/cm2. Deep Level Transient Spectroscopy (DLTS) was used to characterize the induced defects. DLTS studies of Ar+ implanted samples showed six defect levels at EC – 0.18 eV, EC – 0.23eV, EC – 0.31eV, EC – 0.38 eV, EC – 0.72 eV, and EC – 0.81 eV. Z1/Z2 defect is the dominant defect in the electron irradiated sample and anneals out completely after 10 minutes at 1000 °C. However, Z1/Z2 defect in Ar+ implanted samples was stable up to 1600 °C. It is suggested that the annealing behavior of Z1/Z2 depends on the source of its formation.
Laser Direct Write and Gas Immersion Laser Doping Fabrication of SiC Diodes
Authors: Tian Z. , Quick N.R. , Kar A. 
Published: April 2011

AbstractLaboratory prototype SiC diodes are fabricated using a combination of gas immersion laser doping (GILD) and laser direct write (LDW) in situ metallization in a commercial SiC wafer. Trimethylaluminum (TMA) and nitrogen are the precursors used to produce p-type and n-type SiC, respectively. Using these techniques, a 150 nm p-type doped junction is fabricated in semiinsulating 6H-SiC and n-doped 4H-SiC wafers. Ohmic contacts are created by laser direct metallization producing carbon rich conductive phases in these doped materials. Alternatively an excimer laser can be used to create silicon rich Schottky contacts. The geometry of the diodes can be vertical or planar to the wafer surface and the laser processes are thought to reduce defect densities in the irradiated areas. These laser-processed diodes are intended for use in high temperature, high voltage and high frequency switching and sensing applications.
Sic Power Diodes Improvement by Fine Surface Polishing
Authors: Godignon P. , Perez R. , Tournier D. , Mestres N. , Mank H. , Turover D. 
Published: April 2011

AbstractSurface treatment is a key technological parameter in the microelectronics technology and especially for SiC devices since high temperatures must be used for implanted impurities annealing and crystal damage recovery. In this work we take profit of a novel fine polishing process developed by NOVASIC to improve the electrical characteristics of Boron and Aluminium implanted Schottky diodes, which are surface quality highly sensitive devices. The mentioned fine polishing process allows to remove a layer thickness of 100nm to 3000nm on the surface of a processed SiC wafer, reducing the surface roughness to RMS of 1Å. The impact of this process on the electrical properties of the samples shows a general improvement of characteristics reproducibility, reduction of leakage current and improvement of breakdown of Boron implanted diodes.
Deep Level Defects in He-implanted n-6H-SiC Studied by Deep Level Transient Spectroscopy
Authors: Chen X. D. , Ling C. C. , Fung S. , Beling C. D. , Wu H. S. , Brauer G. , Anwand W. , Skorupa W. 
Published: April 2011

AbstractDeep level transient spectroscopy (DLTS) was used to study deep level defects in He-implanted n-type 6H-SiC samples. Low dose He-implantation (fluence ∼2×1011 ions/cm2) has been employed to keep the as-implanted sample conductive so that studying the introduction and the thermal evolution of the defects becomes feasible. A strong broad DLTS peak at 275K-375K (called signal B) and another deep level at EC-0.50eV were observed in the as-implanted sample. The intensity of the peak B was observed to linearly proportional to the logarithm of the filling pulse width, which is a signature for electron capture into a defect related to dislocation. After annealing at 500°C, the intensity of peak was significantly reduced and the remained signal has properties identical to the well known Z1/Z2 deep defects, although it is uncertain whether the Z1/Z2 exist in the as-implanted sample or it is the annealing product of the dislocation-related defect. The E1/E2 defect (EC-0.3/0.4eV) was not presence in the as-implanted sample, but was observed after the 300°C annealing.
Modified Abrasives based on fumed SiO2 and Al2O3 for the Cu CMP Process
Authors: Zeidler D. , Bartha J.W. , ortz W.L , Brandes R. 
Published: April 2011

AbstractNew abrasive particles based on SiO2 and Al2O3 were produced with different coating and doping. Seven specifically designed particles were dispersed to prepare slurries for Cu CMP. Glycin was used as complexing agent and hydrogenperoxid as oxidizer. The experimentally obtained removal rate, selectivity, surface quality and planarisation ability, demonstrate a significant impact of the different abrasives tested. SiO2 particles covered with Al2O3 increased the removal rate for Cu. In comparison to this behavior, a low rate for TaN proved a high selectivity copper removal required by the Cu CMP process. A new method for the planarisation length monitoring (step polish response) shows also significant differences in planarisation length (PL) by the polish of copper with slurries composed of these new particles.
Effects of Annealing Atmosphere on the Characteristics and Optical Properties of SiON Films Prepared Plasma Enhanced Chemical Vapor Deposition
Authors: Yun Ki-Jun , Jung Dong-Ryeol , Hong Sung-Kil , Moon Jong-Ha , Kim Jin-Hyeok 
Published: April 2011

AbstractSiON thin films were deposited by plasma-enhanced chemical vapor deposition method at 350 °C using N2O/SiH4 gas mixtures as precursors. As-deposited SiON films were annealed in different gas atmospheres (air, N2, and O2) and at different annealing temperatures (800 oC ∼ 1100 oC). Effects of annealing atmosphere on the Si-O, Si-N, Si-H, and N-H bonding characteristics in SiON films and their structural and optical properties have been investigated. Cross-sectional and planar microstructures were characterized by scanning electron microscopy and atomic force microscopy, and crystallinity was investigated by X-ray diffraction. Chemical bonding characteristics and optical properties SiON films were studied using fourier transform infrared spectroscopy and prism coupler. Xray diffractions showed no evidence of any crystals in all SiON films. The deposition rate strongly depended on the processing parameters such as radio frequency (rf) power, N2O/SiH4 flow ratio, and SiH4 flow rate. Deposition rate increased as N2O/SiH4 flow ratio increased and SiH4 flow rate increased. It was possible to obtain SiON films with surface roughness of about 1 nm and a high deposition rate of about 4 μm/h when the processing parameters were optimized as rf power of 200 W, N2O/SiH4 flow ratio of 3, SiH4 flow rate of 100 sccm. It was observed that the intensity and the shift of the Si-O stretch and Si-N peaks depended on the annealing atmosphere as well as the annealing temperature. The intensity of Si-O peaks increased in the samples annealed in oxygen atmosphere, but it decreased in the samples annealed in nitrogen atmosphere. The intensity of Si-N peak decreased in the samples annealed in oxygen atmosphere, but it increased in the samples annealed in nitrogen atmosphere. The position of Si-O peaks shifted from 1030 nm to 1140 nm in the samples annealed both in oxygen and in nitrogen atmosphere. It was also observed that the intensities of Si-H (∼2250 cm−1) and N-H (∼3550 cm−1) peaks decreased apparently as the annealing temperature increased in all annealed samples.
Eu-doped Yttria and Lutetia Thin Films Grown on Sapphire by PLD
Authors: Bär S. , Scheife H. , Huber G. , Gonzalo J. , Perea A. , Font A. Climent , Paszti F. , Munz M. 
Published: April 2011

AbstractThis paper focuses on the preparation and characterization of crystalline thin films of rare-earth-doped sesquioxides (Y2O3 and Lu2O3) grown by pulsed laser deposition on single-crystal (0001) sapphire substrates. The crystal structure of the films (thicknesses between 1 nm and 500 nm) was determined by X-ray diffraction and surface X-ray diffraction analysis. These measurements show that the films were highly textured along the <111> direction. Using Rutherford backscattering analysis the correct stoichiometric composition of the films could be proved. The surface morphology of the thin films has been studied using atomic force microscopy. Crystalline films show a triangular surface morphology, which is attributed to the <111> growth direction. The emission and excitation spectra of the Eu-doped films down to a thickness of 100 nm look similar to those of the corresponding crystalline bulk material, whereas films with a thickness ≤ 20 nm show a completely different emission behaviour.
Self-Organization of Nanoscopic Building Blocks into Ordered Assemblies
Authors: Horsch Mark A. , Iacovella Christopher R. , Zhang Zhenli , Glotzer Sharon C. 
Published: April 2011

AbstractWe studied the self-assembly of nanoscopic building blocks comprised of polymer-tethered nanoparticles using computer simulation and predict that these building blocks can assemble into mono- and multi-layer sheets and shells. The simulations further demonstrate that for some nanoparticle geometries and tethered nanoparticle topologies, ideas from block copolymers, surfactants and liquid crystals can be used to predict the ordered morphologies attained via self- assembly and that for specific cases the morphologies are consistent with Israelachvili packing rules.
Confinement of Nanocrystals and Possible Charge Storage Mechanism for MIS Memory Devices with Ge Nanocrystals Embedded in SiO2
Authors: Ho V. , Choi W.K. , Chim W.K. , Teo L.W. , Du A. Y. , Tung C. H. 
Published: April 2011

AbstractMemory effect in a metal-insulator-silicon (MIS) structure with the insulator layer consisting of a sputtered capping SiO2 / Ge nanocrystals embedded in SiO2/ rapid thermal oxide structure has been observed. For the devices with a co-sputtered SiO2+Ge middle layer, larger nanocrystals were formed devices with a higher Ge concentration. It was noted that for such devices, the RTO and the capping oxide layers were able to confine the nanocrystals within the middle layer to some extent. However, in devices with pure sputtered Ge middle layer, the RTO and capping oxide layers were not as effective in confining the Ge nanocrystals. In addition, we have consistently observed memory effect from devices annealed in Ar and the absence of memory effect from devices annealed in forming gas. However, Ge nanocrystals were found in devices annealed in both ambient. This implies that having nanocrystals does not necessarily imply the presence of charge storage or memory effect.