bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fatigue Study of a Zr-Ti-Ni-Cu-Be Bulk Metallic Glass
Authors: Wang G. Y. , Liaw P. K. , Peker A. , Yang B. , Benson M. L. , Yuan W. , Peter W. H. , Huang L. , Freels M. , Buchanan R. A. , Liu C. T. , Brooks C. R. 
Published: April 2011

ABSTRACTHigh-cycle fatigue (HCF) studies were performed on zirconium (Zr)-based bulk metallic glasses (BMGs): Zr41.2Ti13.8Ni10Cu12.5Be22.5, in atomic percent. The HCF experiments were conducted using an electrohydraulic machine at a frequency of 10 Hz with a R ratio of 0.1 and under tension-tension loading, where R = σmin./σmax., where σmin. and σmax. are the applied minimum and maximum stresses, respectively. The test environment was air. A high-speed and high-sensitivity thermographic-infrared (IR) imaging system has been used for nondestructive evaluation of temperature evolution during fatigue testing of BMGs. Limited temperature evolution was observed during fatigue. However, no sparking phenomenon was observed at the final moment of fracture of this BMG. At high stress levels (σmax. > 864 MPa), the fatigue lives of Batch 59 are longer than those of Batch 94 due to the presence of oxides in Batch 94. Moreover, the fatigue-endurance limit of Batch 59 (703 MPa) is somewhat greater than that of Bath 94 (615 MPa) in air. The fatigue-endurance limit of Ti-6–4 is greater than this BMG, but Al 7075 has the lowest fatigue life. The vein pattern with a melted appearance were observed in the apparent melting region. The fracture morphology indicates that fatigue cracks initiate from some defects.
Evolution of the Free Volume during Homogeneous Flow of a Metallic Glass
Authors: Heggen M. , Spaepen F. , Feuerbacher M. 
Published: April 2011

ABSTRACTGlassy Pd41Ni10Cu29P20 was creep-tested in compression at constant true stress. The defect concentrations were shown to be reversible with reproducible kinetics. The results could be fit better with a defect creation rate that is proportional to the applied power density than with one that depends on the strain rate only. The dilatation mechanism for creation of free volume is inefficient in energy and generation of free volume.
MECHANICAL BEHAVIOR OF BULK GLASSY Fe65.5Cr4Mo4Ga4P12C5B5.5
Authors: Stoica Mihai , Radtke Nicolle , Eckert Jürgen , Roth Stefan , Alcalá Germán , Gebert Annett , Schultz Ludwig , Wang Wei Hua , Zhao Yan Hui 
Published: April 2011

ABSTRACTThe bulk amorphous Fe-based alloy with the nominal composition Fe65.5Cr4Mo4Ga4P12C5B5.5 was obtained by copper mold casting in different shapes: cylindrical rods with diameters up to 2.5 mm and discs with 10 mm diameter and 1 mm thickness. This alloy exhibits good soft magnetic properties. Using electrochemical investigations we found that the corrosion resistance of this alloy is better than that of usual FeSi steel used for magnetic applications. Beside magnetic properties and corrosion resistance, this alloy exhibits also good mechanical properties. These were investigated by compression tests, nanoindentation and by an ultrasonic technique. The Young's modulus E was found to be around 160 GPa, the yield strength σy is around 2.3 GPa and the fracture strength σf is around 3.23 GPa, together with an elastic strain εe= 1.5% and a fracture strain εf= 2.3%. The hardness was found to be around 10 GPa.
Phase Transitions in Al87Ni7Nd6
Authors: Louca Despina , Ahn K. , Soper A. K. , Poon S. J. , Shiflet G. J. 
Published: April 2011

ABSTRACTThe local atomic structure of Al87Ni7Nd6 amorphous metallic glass was determined upon heating by neutron diffraction and the pair density function (PDF) analysis. Two isotopes of Ni with very different scattering intensities were used (58Ni and 60Ni) to separate the local environment of the transition metal. A distinct pre-peak observed in reciprocal space arises because of chemical clustering of Ni atoms. With increasing temperature the coherence length of this peak increases indicating an enhancement in atomic clustering. In addition, precipitation of Al metal is first observed at 200 °C with heating. Binary and ternary Al phases form as the temperature increases further to 500 °C although the majority crystalline phase is Al. The local atomic topology at the intermediate temperatures can be represented with a model that is a combination of the atomic structure at room temperature plus Al.
On the Structural Characterization of a Series of Novel Ni-Nb-Sn Refractory Alloy Glasses
Authors: Tokarz Michelle L. , Bilello John C. 
Published: April 2011

ABSTRACTRecently refractory alloy glasses of varying Ni, Nb and Sn concentrations were prepared and studied via several characterization methods, including x-ray diffraction via standard lab and synchrotron radiation sources, SEM, and other complementary techniques. A comparison between x-ray diffraction results obtained from synchrotron sources vs. standard lab sources shows the necessity of a low-divergence source in order to distinguish nanoscale crystallites present within an amorphous matrix. The divergence of both sources was determined by comparing the diffraction patterns of a LaB6standard and noting the deviation from ideal or theoretical Bragg peaks. The crystallites in these glasses comprised between 0 and 7.5 percent by volume, depending upon the specific composition. The results presented here also show a very good sample-to-sample consistency for any given alloy composition. While x-ray diffraction results give information about the average structure, SEM was also performed to understand aspects of individual crystallite size and distribution. By studying results of varying alloy concentrations, it is seen that a very small composition range exists for near-perfect glass formers (as defined by a near zero percentage crystallinity). Radial distribution analysis was also performed for each composition and compared to hard sphere models for each alloy composition. This analysis indicated the presence of intermediate range order beyond the first nearest neighbors as indicated by the divergence of the experimental reduced radial distribution functions from that predicted by the accompanying hard sphere models.
Impact of Ge diffusion and wafer cross hatching on strained Si MOSFET electrical parameters
Authors: L. Driscoll , S. Olsen , S. Chattopadhyay , A. O'Neill , K. Kwa , P. Dobrosz , S. Bull 
Published: April 2011

ABSTRACTA contender for future generations of CMOS technology is the strained silicon (S-Si) MOSFET. The mobility enhancement in S-Si can be exploited to maintain the performance enhancements demanded by Moore's law with reduced critical dimensions. S-Si is obtained by growth of a thin Si layer over a thick virtual substrate (VS) of relaxed silicon-germanium (SiGe). The mobility of a surface channel MOSFET is dependent on the quality of the silicon-oxide (Si/SiO2) interface. Ge may out diffuse from the virtual substrate to the oxide interface causing an increase in trapping density. As the Ge content in the virtual substrate increases surface roughness also increases. These phenomena both lead to a reduction in mobility.The study of a matrix of devices having variable Ge composition and S-Si thickness is crucial in deconvolving the contributions of Ge diffusion and wafer cross-hatching roughness on electrical parameters. Increasing VS Ge composition increases the Ge concentration at the SSi/SiO2 interface and cross-hatching amplitude whereas reducing S-Si channel thickness only increases Ge concentration at the S-Si/SiO2 interface and does not increase cross-hatch amplitude. Interface state density, drive current, gate leakage current, transconductance and carrier mobility data are presented for this two-dimensional space of VS composition and S-Si thickness. The relative importance of Ge diffusion and cross-hatching roughness can be seen in this data. The results of this study indicate a lower limit of 7 nm for the S-Si thickness and an upper limit of approximately 20 % Ge in the virtual substrate for the current processing technology. Understanding the performance-limiting mechanisms in S-Si is crucial in the optimisation of VS Ge composition and S-Si thickness for current and future generations of S-Si CMOS.
Material and optical properties of GaAs grown on (001) Ge/Si pseudo-substrate
Authors: Chriqui Yves , Largeau Ludovic , Patriarche Gilles , Saint-Girons Guillaume , Bouchoule Sophie , Bensahel Daniel , Campidelli Yves , Kermarrec Olivier , Sagnes Isabelle 
Published: April 2011

ABSTRACTOne of the major challenges during recent years was to achieve the compatibility of III-V semiconductor epitaxy on silicon substrates to combine opto-electronics with high speed circuit technology. However, the growth of high quality epitaxial GaAs on Si is not straightforward due to the intrinsic differences in lattice parameters and thermal expansion coefficients of the two materials. Moreover, antiphase boundaries (APBs) appear that are disadvantageous for the fabrication of light emitting devices. Recently the successful fabrication of high quality germanium layers on exact (001) Si by chemical vapor deposition (CVD) was reported. Due to the germanium seed layer the lattice parameter is matched to the one of GaAs providing for excellent conditions for the subsequent GaAs growth. We have studied the material morphology of GaAs grown on Ge/Si PS using atomic layer epitaxy (ALE) at the interface between Ge and GaAs. We present results on the reduction of APBs and dislocation density on (001) Ge/Si PS when ALE is applied. The ALE allows the reduction of the residual dislocation density in the GaAs layers to 105 cm−2 (one order of magnitude as compared to the dislocation density of the Ge/Si PS). The optical properties are improved (ie. increased photoluminescence intensity). Using ALE, light emitting diodes based on strained InGaAs/GaAs quantum well as well as of In(Ga)As quantum dots on an exactly oriented (001) Ge/Si pseudo-substrate were fabricated and characterized.
Measurement of the residual macro and microstrain in strained Si/SiGe using Raman spectroscopy
Authors: Dobrosz P. , Bull S.J. , Olsen S.H. , O'Neill A.G. 
Published: April 2011

ABSTRACTThe use of laser Raman spectroscopy to assess the residual strain in strained silicon/silicon germanium devices is well established. The peak shift associated with the 520cm−1 silicon peak can be used to directly measure the strain in the cap layer provided that the strained silicon peak can be deconvoluted from the more intense Si in SiGe peak which occurs at slightly lower wavenumbers. However, though peak position gives a measure of the macrostrains in the layer it is not useful for the assessment of microstrains associated with point defects which may also influence device performance; such microstrains influence the intensity of the Raman peaks and can, in principle, be monitored by this method. In this study we have undertaken a study of peak shape as a function of processing conditions for strained silicon on SiGe. Changes in peak position may be correlated with macrostrains and macrostrain relaxation around extended defects such as dislocations. Changes in peak width can be correlated with processes which lead to changes in composition (e.g. germanium build-up in the surface after etching) and microstrain. Such changes are not necessarily correlated with changes in macrostrain but indicate that microstrain could also be an important factor influencing device performance.
Retarded Growth of Sputtered HfO2 Films on Germanium
Authors: Kita Koji , Sasagawa Masashi , Toyama Masahiro , Kyuno Kentaro , Toriumi Akira 
Published: April 2011

ABSTRACTHfO2 films were deposited by reactive sputtering on Ge and Si substrates simultaneously, and we found not only the interface layer but the HfO2 film was thinner on Ge substrate compared with that on Si substrate. A metallic Hf layer has a crucial role for the thickness differences of both interface layer and HfO2 film, since those thickness differences were observed only when an ultrathin metallic Hf layer was predeposited before HfO2 film deposition. The role of metallic Hf is understandable by assuming a formation of volatile Hf-Ge-O ternary compounds at the early stage of film growth. These results show an advantage of HfO2/Ge over HfO2/Si systems from the viewpoint of further scaling of electrical equivalent thickness of the gate oxide films.
Diffusion of ion-implanted Boron and Silicon in Germanium
Authors: Uppal Suresh , Willoughby A. F. W. , Bonar J. M. , cowern N. E. B. , Morris R. J. H. , Dowsett M. G. 
Published: April 2011

ABSTRACTThe diffusion of B and Si in Ge is studied using implantation doping. Concentration profiles after furnace annealing in the temperature range 800–900 °C were obtained using high resolution secondary ion mass spectroscopy (SIMS). Diffusion coefficients are calculated by fitting the annealed profiles. For B, we obtain diRusivity values which are two orders of magnitude slower than previously reported in literature. An activation energy of 4.65(±0.3) eV is calculated for B diffusion in Ge. The results suggest that diffusion mechanism other than vacancy should be considered for B diffusion in Ge. For Si diffusion in Ge, the diffusivity values calculated in the temperature range 750–875 °C are in agreement with previous work. The activation energy of 3.2(±0.3) eV for Si diffusion is closer to that for Ge self-diffusion which suggests that Si diffusion in Ge occurs via the same mechanism as in Ge self-diffusion.
Influence of He implantation conditions on strain relaxation and threading dislocation density in Si0.8Ge0.2 virtual substrates
Authors: Cai J. , Mooney P. M. , Christiansen S. H. , Chen H. , Chu J. O. , Ott J. A. 
Published: April 2011

ABSTRACTThe strain relaxation and threading dislocation density of He-implanted and annealed SiGe/Si heterostructures have been studied. For He doses above a threshold of 8×1015 cm−2, the degree of strain relaxation depends primarily on the SiGe layer thickness; a similar degree of strain relaxation is obtained when the He dose and energy are varied over a relatively wide range. In contrast, the threading dislocation density is strongly influenced by the implantation depth. There is a strong correlation between the parameter He(SiGe), the He dose in the SiGe layer calculated from He profiles simulated using the program Stopping and Range of Ions in Matter (SRIM), and the threading dislocation density. We find that to achieve a low threading dislocation density, <5×107 cm−2, He(SiGe) must be less than 1015 cm−2. The strain relaxation mechanism is also discussed.
Structure of Sc2O3 Films Epitaxially Grown on α-Al2O3 (111)
Authors: Kortan A. R. , Hong M. , Kwo J. , Chang P. , Chen C. P. , Mannaerts J. P. , Liou S. H. 
Published: April 2011

ABSTRACTWe have characterized the structure of the epitaxial Sc2O3 films grown on a α-Al2O3 (111) substrate using molecular beam epitaxy (MBE) techniques. The Sc2O3 films grow in the bulk bixbyite phase with a very uniform thickness, and a high structural perfection. They grow with their cubic (111) axis parallel to the rhombohedral (111) axis of the sapphire substrate. The in-plane orientation of the films, however, is rotated by ±30 degrees with respect to the substrate rhombohedral axes. This is explained by the presence of two equivalent orientations of the 3-fold axis of the film on the quasi 6-fold surface of the substrate.
Photo-induced magnetism of Pr0.65Ca0.35MnO3 in powder and thin films
Authors: Otagiri Takanobu , Arai Masato , Kodaira Masakazu , Yanagisawa Osami , Izumi Mitsuru 
Published: April 2011

ABSTRACTThe photo-induced magnetism was originally found in Pr0.65Ca0.35MnO3 powder by the ESR and x-ray diffraction studies. However, the mechanism of the photo-induce magnetism was under cover for a long time. Now, D.C. magnetization measurement under a near infrared pulsed laser irradiation (hν = 1.18 eV) reveals the mechanism. The D.C. magnetization prominently increases (approximately 6 %) under the laser irradiation, especially around 90 K near the canted antiferromagnetic (CAF) – antiferromagnetic (AF) transition. The result is consistent with the previous studies and indicates that a CAF – ferromagnetic transition is caused associating with the charge-order (CO) – charge-delocalize (CD) (insulator – metal) transition by the laser irradiation. As the second step for development, the thin films were prepared with the pellet of Pr0.65Ca0.35MnO3 in the on-axis and off-axis geometry of RF magnetron sputtering deposition. The off-axis geometry provides the Pr0.65Ca0.35MnO3 film same as powder composition and the on-axis sputtering fortunately provides the Pr0.99Ca0.01MnO3 film. Both films show photo-induced magnetism. The present photo-induced magnetism is coming from a spin-canted phase in both compounds.
Persistent Electronic Conduction in 12CaO7Al2O3 Thin Films Produced by Ar Ion Implantation: Selective Kick-Out Effect Leads to Electride Thin Films
Authors: Miyakawa Masashi , Hayashi Katsuro , Toda Yoshitake , Kamiya Toshio , Hirano Masahiro , Hosono Hideo 
Published: April 2011

ABSTRACTA new method to convert 12CaO7Al2O3 (C12A7) thin films to electronic conductor by hot Ar+ ion implantation has been developed and its mechanism is discussed. It was found that hot Ar+ ion implantation extruded free O2- ions in C12A7 films by kick-out effects at fluences higher than 1×1017 cm−2, which left electrons in the cages embedded in C12A7 crystal and produced high concentration F+-like centers (∼1.4×1021 cm−3). The resulting films show coloration and persistent electronic conduction with conductivities up to ∼1 Scm−1. On the other hand, fluences less than 1×1017 cm−2 kept the films transparent and insulating.
High Mobility Nanocrystalline Indium Zinc Oxide Deposited at Room Temperature
Authors: Fortunato E. , Pimentel A. , Gonçalves A. , Marques A. , Martins R. 
Published: April 2011

ABSTRACTIn this paper we present results of indium doped zinc oxide deposited at room temperature by rf magnetron sputtering, with electron mobility as high as 60 cm2/Vs. The films present a resistivity as low as 5 × 10-4 ωcm with an optical transmittance of 85%. The structure of these films look-like polymorphous (mixed of different amorphous and nanocrystalline phases from different origins) as detected from XRD patterns (no clear peak exists) with a high smooth surface, as detected from SEM micrographs, highly important to ensure long life time when used in display devices.
Guided Control of Cu2O Nanodot Self-Assembly on SrTiO3 (100)
Authors: Du Yingge , Atha Surajit , Hull Robert , Groves James F. , Lyubinetsky Igor , Baer Donald R. 
Published: April 2011

ABSTRACTA method has been developed for specifying the growth location of Cu2O nanodotson SrTiO3 (100) substrates. Growth location has been specified by using a focused ion beam (FIB) to modify microscopic and nanoscopic regions of the SrTiO3substrate prior to Cu2O deposition. Deposition onto the modified regions under carefully selected process conditions has generated nanodot growth at the edge of microscopic FIB-induced features and on top of nanoscopic FIB-induced features. For this work, an array of evenly spaced FIB implants was first patterned into several regions of each substrate. Within each sub-division of the array, the FIB implants were identical in Ga+ energy and dosage and implant diameter and spacing. After FIB surface modification and subsequent in-situ substrate cleaning, Cu2O nanodots were synthesized on the patterned SrTiO3 substrates using oxygen plasma assisted molecular beam epitaxy. The substrates and nanodots were characterized using atomic force microscopy at various stages of the process; in-situ X-ray photoelectron spectroscopy and Auger electron spectroscopy analysis demonstrated that the final stoichiometry of the nanodots was Cu2O. The photocatalytic decomposition of water on Cu2O under visible light irradiation has been reported. If the Cu2O can be located in the form ofislands on a carefully selected substrate, then it could be possible to greatly enhance the efficiency of the photochemical process.
Hydrogen induced degradation in GaInP/GaAs HBTs revealed by low frequency noise measurements
Authors: Tartarin J.G. , Escotte L. , Borgarino M. , Plana R. , Graffeuil J. 
Published: April 2011

ABSTRACTOne of today's challenges to enable the improved electrical performances and reliability of microelectronic devices consists in controlling impurities contamination: hydrogen appears to be present in most (if not all) the processes steps of the devices making (ambient atmosphere, or associated with AsH3 -VPE or AsCl3 -VPE for example in GaAs based devices,…). Hydrogen induced reliability has already been investigated for many Si or GaAs based technologies ((C)MOS, FET, HEMT, PHEMT as well as HBT devices). These effects of hydrogen on electrical behavior and on long term reliability are very difficult to understand because of the different nature and ionic association of hydrogen (H, H+, H-, H2, or associated with impurities (Ge-H, Be-H, C-H,…). Most of these studies make use of IR, SIMS, Hall measurements: in this paper, we use low frequency noise measurements, associated with static as well as dynamic characterization to identify the degradation process in GaInP/GaAs Heterojunction Bipolar Transistors (HBT supplied by Thomson LCR). The presence of Hydrogen has been identified by DLTS at the LPSC laboratory (Meudon, France). The influence of passivation (SiN and GaInP ledge) on the reliability associated with Hydrogen has been one of the first improvements on HBT devices. Low-frequency noise measurements have been performed in the range of 250Hz to 100 kHz. The noise spectra evolutions (current and voltage noise sources at the input of the devices) allowed us to identify the activation process responsible of the static and dynamic rise and fall of the HBT's current gain. Chemical reactions of C-H complexes have been proved to be the processes responsible of this degradation. Additive reliability tests have been performed on two sets of devices (featuring different emitter length) under two distinct stocking conditions (temperature and biasing of the devices) leading to different junctions temperatures: low-frequency (LF) noise measurements, associated with static and dynamic S parameter measurements led to the same conclusion about the involved chemical reaction. We found that C-H complexes break, and H diffusion towards the extrinsic surface of the device has been observed on the measured leakage currents. Sealed devices have proved to get the same degradation signature than on wafer devices: Hydrogen is assumed to be present in high concentration levels in the device layers, and reacts under thermal and electrical stress.
Deciphering the Vibrational Spectrum of Interstitial H2 in Si
Authors: Stavola Michael , Chen E Elinor , Fowler W. Beall 
Published: April 2011

ABSTRACTH2 is a fascinating molecule whose properties revealed the influence of nuclear spin on the molecular wave function in the 1920s. As an interstitial defect in Si, the H2 molecule has given rise to a number of perplexing puzzles since the discovery of its vibrational spectrum. The absence of an ortho-para splitting for the H2 vibrational line and an apparent low symmetry found in stress experiments misled several researchers into thinking that interstitial H2 in Si must have a barrier to rotation. Our discovery of a new vibrational line for HD in Si and its interpretation, along with the recognition that certain transitions are possible for HD, but not for H2 or D2, establish that H2 in Si is a nearly free rotator after all. Additional puzzles such as the anomalous intensity of the HD line, the absence of an isotope dependence for the uniaxial stress splitting of the H2 and D2 vibrational lines, and the properties of an O-H2 complex are also explained naturally. Recent Raman studies confirm that interstitial H2 in Si is a free rotator but raise interesting new questions about the diffusivities of the ortho and para species.