bluuebunny/crossref_metadata_2025_split huggingface dataset:
Free Volume Changes and Crack Tip Deformation in Bulk Metallic Glass Alloys and their Composites
Authors: Kanungo Biraja P. , Lambert Matthew J. , Flores Katharine M. 
Published: April 2011

ABSTRACTThe free volume changes associated with deformation of metallic glasses play an important role in strain localization in shear bands. However the details of these structural changes during inhomogeneous deformation are unclear. In this study, the free volume changes in Cu60Zr30Ti10 and Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 bulk metallic glasses were examined and quantified using differential scanning calorimetry following rolling and low temperature annealing. It was found that the height of the endothermic peak associated with the glass transition decreased following deformation whereas annealing resulted in an increase in the peak height. Additionally, the exothermic event associated with structural relaxation prior to the glass transition occurred at a lower temperature after rolling in the Zr-based system. Surprisingly, a similar shift in the onset temperature was not observed in the Cu-based system, suggesting a different structural relaxation mechanism. The Zr-based system was successfully modeled and the results indicated that the free volume increased ∼4% with inhomogeneous deformation and decreased ∼14% with annealing, consistent with expectations. In an effort to further characterize strain localization in shear bands, the development of a crack tip damage zone in a Zr-based bulk metallic glass composite was studied using scanning electron and atomic force microscopy. The first shear band developed at an angle of ∼60° from the crack propagation direction. This is discussed in light of the Mohr-Coulomb yield criterion for metallic glasses. The reinforcement phase arrested the growth of individual shear bands, while accumulated damage resulted in the shear bands cutting through the crystalline phase, ultimately resulting in crack branching and failure.
Microstructure of Ti-Based, Dendrite/Nanostructured-Matrix Composites
Authors: Woodcock Thomas G. , Mato Sonia , Alcalá Germán , He Guo , Wang Yinmin , Ma En , Dai Qunlong , Sui Manling , Löser Wolfgang , Eckert Jürgen , Schultz Ludwig 
Published: April 2011

ABSTRACTElectron microscopy of the composite-forming alloys Ti60Cu14Ni12Sn4Nb10 and Ti60Cu14Ni12Sn4Ta10, shows that for both alloys, the microstructure consists of an array of micron-scale dendrites surrounded by a nanoscale binary eutectic. In the Ta-containing alloy, one of the eutectic phases has been identified as having a bcc crystal structure similar to that of the dendrites. In the Nb-containing alloy, one of the eutectic phases has been found to have a similar composition to that of the dendrites. Further detailed structural and compositional characterization is needed in order to understand the solidification behaviour of such materials. This knowledge may then be used to improve the casting conditions and subsequent mechanical properties of the materials.
Structural Relaxation and Crystallization in a Pd40Cu30Ni10P20 Bulk Metallic Glass
Authors: Raghavan R. , Ramamurty U. , Basu J. , Ranganathan S. , Nishiyama N. 
Published: April 2011

ABSTRACTThe stability of a Pd40Cu30Ni10P20 bulk metallic glass (BMG) against structural relaxation is investigated by isothermal and isochronal annealing heat treatments below and above its glass transition temperature, Tg, for varying periods. Differential scanning calorimetry (DSC) of the annealed samples shows an excess endotherm at Tg, irrespective of the annealing temperature. This recovery peak evolves exponentially with annealing time and is due to the destruction of anneal-induced compositional short range ordering. The alloy exhibits a high resistance to crystallization on annealing below Tg and complex Pd- and Ni-phosphides evolve on annealing above Tg.
(Selective) Epitaxial Growth of Strained Si to Fabricate Low Cost and High Performance CMOS Devices
Authors: Loo R. , Delhougne R. , Meunier-Beillard P. , Caymax M. , Verheyen P. , Eneman G. , Wolf I. De , Janssens T. , Benedetti A. , Meyer K. De , Vandervorst W. , Heyns M. 
Published: April 2011

ABSTRACTTensile strained Si on SiGe Strain Relaxed Buffers (SRB) is an interesting candidate to increase both electron and hole mobility which results in improved device performance. Most of this work was/is based on thick (several μm), step-graded SRBs with or without Chemical Mechanical Polishing (CMP) planarisation. This approach bears several disadvantages such as issues with STI formation in the thick SiGe structure, and considerable self-heating effects due to the lower thermal conductivity of the SiGe material. Further, pMOS improvement requires SRBs with high Ge contents (> 30 %), which complicates device fabrication even more. To overcome these issues, we developed a new and cost efficient type of thin SRB (∼200 nm). The concept is based on the introduction of a thin carbon-containing layer during growth of a constant composition SiGe layer. The process relies on standard Chemical Vapor Deposition epitaxial technology without need for CMP. It is designed to allow both non-selective growth on blanket wafers and selective growth in the active area of structured wafers with Shallow Trench Isolation (STI). The selective epitaxial process for strained Si on thin SRBs proposed here, allows relatively simple and cost-effective fabrication of strained Si layers on existing STI structures without any process modification. Further, it offers a very flexible fabrication scheme to independently improve nMOS and pMOS devices. The SRB quality is comparable to the best reported in literature so far, with 70 % and 53 % mobility enhancements for long channel nMOSFETs on 22 % Ge SRBs grown on blanket and STI patterned wafers, respectively.
Strained Silicon On Insulator wafers made by the Smart Cut™ technology
Authors: Ghyselen B. , Bogumilowicz Y. , Aulnette C. , Abbadie A. , Osternaud B. , Besson P. , Daval N. , Andrieu F. , Cayrefourq I. , Moriceau H. , Ernst T. , Tiberj A. , Rayssac O. , Blondeau B. , Mazure C. , Lagahe-Blanchard C. , Pocas S. , Cartier A.-M. , Hartmann J.-M. , Leduc P. , Nardo C. Di , Lugand J.-F. , Fournel F. , Semeria M.-N. , Kernevez N. , Campidelli Y. , Kermarrec O. , Morand Y. , Rivoire M. , Bensahel D. , Paillard V. , Vincent L. , Claverie A. , Boucaud P. 
Published: April 2011

ABSTRACTStrained Silicon On Insulator wafers are today envisioned as a natural and powerfulenhancement to standard SOI and/or bulk-like strained Si layers. For MOSFETs applications, thisnew technology potentially combines enhanced devices scalability allowed by thin films andenhanced electron and hole mobility in strained silicon. This paper is intended to demonstrate byexperimental results how a layer transfer technique such as the Smart Cut™ technology can be usedto obtain good quality tensile Strained Silicon On insulator wafers. Detailed experiments andcharacterizations will be used to characterize these engineered substrates and show that they arecompatible with the applications.
Strain Mapping in SiGe by Visible Raman Spectroscopy
Authors: Pajcini Vasil 
Published: April 2011

ABSTRACTHeterogeneous strain in Si/SiGe for CMOS mobility enhancement may result in device yield losses or IC performance limitations. This lateral heterogeneity in strain can be uniquely measured by Raman spectroscopy. UV Raman and Visible Raman can measure this heterogeneity respectively in the thin Si cap and in the SiGe underlayer. Both UV and Visible Raman are useful. While UV Raman is optimized for the Si channel layer, Visible Raman of the SiGe underlayer provides diagnostic information when trying to understand and reduce the heterogeneity in the Si channel. In principle Visible Raman can also measure the heterogeneity of the strain in the Si channel, but in practice this is very time consuming and not as sensitive as UV Raman. This paper focuses on the kind of heterogeneity strain information available from Visible Raman.
Physical characterization of HfO2 deposited on Ge substrates by MOCVD
Authors: Elshocht S. Van , Brijs B. , Caymax M. , Conard T. , Gendt S. De , Kubicek S. , Meuris M. , Onsia B. , Richard O. , Teerlinck I. , Steenbergen J. Van , Zhao C. , Heyns M. 
Published: April 2011

ABSTRACTGermanium is because of its intrinsically higher mobility than Si, currently under consideration as an alternative approach to improve transistor performance. Germanium oxide, however, is thermodynamically unstable, preventing formation of the gate dielectric by simple oxidation. At present, high-k dielectrics might be considered as an enabling technology as much progress has been made in the deposition of thin high-quality layers.In this paper, we study the growth and physical properties of HfO2 deposited on Ge by MOCVD, using TDEAH and O2 as precursors, and compare the results to similar layers deposited on silicon substrates. Our results show that the physical properties of MOCVDdeposited HfO2 layers on Ge are very similar to what we have observed in the past for Si. Unfortunately, some of the negative aspects observed for Si, such as diffusion of substrate material in the high-k layer, a low density for thinner layers, or a rough top surface, are also observed for the case of Ge. However, careful surface pretreatments such as NH3 annealing the Ge substrate prior to deposition, can greatly improve the physical properties. An important observation is the very thin interfacial layer between HfO2 and Ge substrate, allowing a more aggressive scaling for Ge.
Island Scaling Effects on Photoluminescence of Strained SiGe/Si (100)
Authors: Peterson Rebecca L. , Yin Haizhou , Sturm J. C. 
Published: April 2011

ABSTRACTThe fabrication of electronic devices on semiconductor islands is becoming increasingly common because of silicon-on-insulator technology and/or because of strain engineering in compliant substrate approaches. While photoluminescence can be an accurate probe of Ge content and strain, in islands it can be affected by the presence of the island edges. Here we present data and a model showing that for high quality SiGe, edge effects are critical for sizes under ∼20 μm. These effects can be mitigated by regrowing epitaxial silicon to passivate the recombination states on the island edges.
Epitaxial La0.67(Sr,Ca)0.33MnO3 Films on Si for IR Bolometer Applications
Authors: Grishin A.M. , Khartsev S.I. , Kim J.-H. , Lu Jun 
Published: April 2011

ABSTRACTWe report on processing and properties of La0.67(Sr,Ca)0.33MnO3(LSCMO) films grown by pulsed laser deposition technique on Si(001) substrates buffered with Bi4Ti3O12/CeO2/YSZ heteroepitaxial layers. X-ray diffraction shows cube-on-cube growth of epitaxial Bi4Ti3O12/CeO2/YSZ/Si heterostructure whereas the LSCMO layer grows in the “diagonal-on-side” manner onto the Bi4Ti3O12 (BTO) template. High resolution TEM images demonstrate sharp interfaces between the buffer layers and LSCMO film as well as rare misfit dislocations on the CeO2/YSZ interface. LSCMO film processing conditions have been optimized to get maximum temperature coefficient of resistivity TCR = 4.4%K-1 and colossal magnetoresistance(CMR) ‘Delta;ρ/ρ ∼ 2.9%kOe-1 @ 294K. Almost ultimate CMR performance at room temperature has been achieved due to successive improvement of c-axisorientation of layers: full widths at half-maximum (FWHM) 0.65, 0.58, 0.65, 1.13 and 0.18 degrees in LSCMO/BTO/CeO2/YSZ/Si stack, respectively. Characterization of electrical noise in CMR film yields noise equivalent temperature difference (NETD) as low as 1.2 ‘mu;K/√Hz @ 30Hz and 294K.
Preparations and Evaluations of Magnetoelectric Thin Films for Josephson Field Effect Transistor
Authors: Iwata Nobuyuki , Matsuo Koji , Ootsuka Noriaki , Yamamoto Hiroshi 
Published: April 2011

ABSTRACTWe proposed the magnetoelectric (ME) effect as a new function of oxides electronic devices. The ME effect is characterized by the appearance of an induced magnetization with electric field applied and also is true in the opposite way. As one of the oxides devices we proposed a new type of Josephson field effect transistor (JFET) as adopting the ME materials to a gate insulator. In such the device, considering the Fraunhofer pattern, large IC modulation was expected by the induced magnetic field. Representative ME material, Cr2O3 films were deposited on Josephson junctions which were formed bygrain boundaries in YBa2Cu3OX (YBCO) films grown on MgO substrates. The multilayered films, Cr2O3 /YBCO and Cr2O3 / Y2O3 / YBCO were studied as the model of JFET.
Two-Dimensional Electronic Structures in Layered Oxychalcogenide Semiconductors, LaCuOCh (Ch=S, Se, Te) and La2CdO2Se2
Authors: Kamiya Toshio , Ueda Kazushige , Hiramatsu Hidenori , Ohta Hiromichi , Hirano Masahiro , Hosono Hideo 
Published: April 2011

ABSTRACTElectronic structures of layered oxychalcogenides, LaCuOCh (Ch=S, Se, Te) and La2CdO2Se2, were studied using ab-initio band calculations in relation to their optical and electronic properties. It was found that the dispersions of the top valence bands are much smaller in Γ-Z direction than in Γ-X direction, indicating that the electronic structure is highly two-dimensional, and that holes are confined in the CuCh or CdSe layers. The two-dimensional electronic structure is supported experimentally by staircase-like structure observed in optical absorption spectra at 10 K associated with two excitonic absorption peaks split by spin-orbit interaction of Ch ions. La2CdO2Se2has the largest bandgap due to the two-dimensional network structure of CdSe tetrahedra.
Nanoscale Etching of Metallic Perovskites Using STM
Authors: Dahl Ø. , Hallsteinsen S. , Grepstad J. K. , Borg A. , Tybell T. 
Published: April 2011

ABSTRACTIn the present work we use a scanning tunneling microscope to modify the surface structure of epitaxial SrRuO3 thin films. Point and line etching experiments were carried out in ultra-highvacuum, using tungsten tips. The point etchings showed that pulses fired at small (< 4.5V) bias voltages did not bring about any physical modifications of the film surface, while voltages in excess of4.5 V led to etched holes accompanied by mounds. Moreover, well-defined line etching was achieved with atypical depth of approximately two unit cells and linewidths as small as 5 nm. The experiments demonstrate that a scanning tunneling microscope can be used for nanometer-scale patterning of SrRuO3 thin film surfaces.
Non-metastable recombination induced reactions involving hydrogen in SiC
Authors: Koshka Yaroslav , Krishnan Bharat , Mazzola Michael S. 
Published: April 2011

ABSTRACTA brief survey of some of the recent results of recombination-induced defect reactions involving hydrogen in 4H and 6H-SiC is given. A variety of outcomes of such reactions have been observed in hydrogenated 4H and 6H-SiC polytypes under optical excitation at reduced temperature. A few different non-metastable hydrogen-defect complexes can form, including hydrogen complexes with Al and B acceptors, hydrogen complex with Si vacancy, as well as some other non-identified complexes. Electrical measurements indicated strong recombination-induced passivation of the electrical activity of aluminum and boron acceptors in SiC. This passivation resulted in the reduction of the net free hole concentration and even inversion of the conductivity type. It is suggested that optical excitation causes a long-range migration of hydrogen followed by its capture in one or another kind of defect complexes. Further insight in the formation of specific complexes as a result of recombination-induced defect reactions is provided by thermal admittance spectroscopy. Energy gap levels in the regions that remained p-type after hydrogenation as well as in the regions where the conductivity was inverted by the recombination-induced passivation are investigated.
Infrared Spectroscopy of Hydrogen in ZnO
Authors: Mccluskey M.D. , Jokela S.J. 
Published: April 2011

ABSTRACTZinc oxide (ZnO) has shown great promise as a wide band gap semiconductor with optical, electronic, and mechanical applications. Recent first-principles calculations and experimental studies have shown that hydrogen acts as a shallow donor in ZnO, in contrast to hydrogen's usual role as a passivating impurity. The structures of such hydrogen complexes, however, have not been determined. To address this question, we performed vibrational spectroscopy on bulk, single-crystal ZnO samples annealed in hydrogen (H2) or deuterium (D2) gas. Using infrared (IR) spectroscopy, we have observed O-H and O-D stretch modes at 3326.3 cm−1 and 2470.3 cm−1 respectively, at a sample temperature of 14 K. These frequencies are in good agreement with the theoretical predictions for hydrogen and deuterium in an antibonding configuration, although the bond-centered configuration cannot be ruled out. The IR-active hydrogen complexes are unstable, however, with a dissocation barrier on the order of 1 eV.
Hydrogen Bonding in ZnO
Authors: Nickel N. H. , Brendel K. 
Published: April 2011

ABSTRACTHydrogen effusion measurements reveal that the total hydrogen concentration in ZnO ranges from 5.2×1016 cm−3 for single crystal ZnO to 3×1021 cm−3 for polycrystalline ZnO thin-fims. From the H effusion spectra the hydrogen chemical potential is determined as a function of the H concentration that can be related th the H density-of-states distribution. Single crystal ZnO exhibiting the lowest H concentration reveals six peaks in the H density-of-states located between 0.59 and 1.4 eV below the H transport site. With increasing H concentration the amount of H accommodated with binding energies larger than 1.0 eV increases significantly.
Anharmonicity in the Vibrational Modes Associated with H-H, N-H, O-H, and C-H bonds
Authors: Limpijumnong Sukit 
Published: April 2011

ABSTRACTThe anharmonic contributions to the vibrational frequency of various H-H, N-H, O-H, and C-H bond configurations are investigated using first principles calculations. While harmonic approximation can be accurately used to calculate the local vibrational mode of most microscopic configurations, the configurations involving strong X-H bond are exceptions because of the exceptionally light mass of the H atom. We will explicitly present the magnitude of the anharmonic contributions to the total frequencies associated with X-H bonds in free molecules as well as in semiconductors defects.
Impact of Hydrogen Plasma Treatment on Gettering by He Implantation-Induced Cavities in Silicon
Authors: Alquier D. , Ntsoenzok E. , Liu C.L. , Vengurlekar A. , Ashok S. 
Published: April 2011

ABSTRACTThe use of gettering techniques, with precise location of the gettering regions, has become crucial for device manufacturing. Helium-induced cavities have been shown to getter metallic impurities very effectively, but suffer from the drawback of requiring relatively high He doses. In this work, He-implanted Cz wafers of varying resistivity were subjected to hydrogen plasma hydrogenation prior to the cavity-formation anneal. We focus our studies on the cavity layer interactions with metal impurities. XTEM images reveal that hydrogenation increases the cavity radius. Our SIMS results show that the doping level has no influence on the metal gettering efficiency while the addition of plasma hydrogenation tends to decrease it. However, the efficiency can be controlled with the cavity radius which is interesting for future applications of the technique.
Hydrogen passivation of bulk defects and surface in silicon
Authors: Martinuzzi Santo , Palais Olivier 
Published: April 2011

ABSTRACTMonocrystalline and multicrystalline silicon wafers were investigated with boron doping levels in the range 1015 cm−3 to 1016 cm−3, respectively. Hydrogenation of the samples resulted from hydrogen-rich silicon nitride deposition by plasma enhanced chemical vapour deposition on the surface of the wafers. Passivation effects are observed after annealing and evaluated using minority carrier diffusion length (L) measurements, light beam induced current scan maps and lifetime (τ) measurements, by the contact-less phase shift technique. When applied at various excitation frequencies the phase shift technique leads evaluate the surface recombination velocity (S) and the actual bulk lifetime.It was found, in multicrystalline silicon that isolated intragrain defects are well passivated while at grain boundaries and dislocation clusters deep levels are transformed into shallow levels. As a consequence L increases up to 80 % after firing the samples which the back surface was covered by a 2 μm thick aluminium layer. S decreases below 500 cm/s at the front surface covered by the hydrogen rich silicon nitride layer.
How much hydrogen and voids are energetically stable in silicon thin films?
Authors: Morral Anna Fontcuberta i , Vach Holger , Cabarrocas Pere Roca i 
Published: April 2011

ABSTRACTWe have developed a model to account for the effects of hydrogen and voids on the structural stability of silicon thin films. The model is based on both experiments and theory. First, hydrogenated amorphous silicon films (a-Si:H) with various hydrogen contents were obtained by Plasma Enhanced Chemical Vapor Deposition. A linear correlation between hydrogen content and void fraction was observed. By tuning the deposition conditions, polymorphous silicon films with hydrogen contents up to 15%, very small void fractions (0.5%) and excellent electronic properties were also obtained. Density Functional Theory (DFT) calculations were performed to determine the formation energy for four types of silicon tetrahedra of the form Si-SinH4−n (n=1, 2, 3, 4). In our model, these tetrahedral units are considered as the building blocks of the silicon thin films. Considering a homogeneous distribution of hydrogen in the solid, the proportion of the different SiSinH4−n tetrahedra as a function of the hydrogen concentration was calculated. Then, the formation energy of hydrogenated amorphous silicon (a-Si:H) was calculated as a function of the hydrogen content and for various porosities. The model predicts that hydrogen incorporation does render the a-Si:H structure unstable for different hydrogen contents depending on the void fraction. Our results show that polymorphous silicon films with hydrogen concentrations up to 15% can be as stable as standard amorphous silicon with 2% hydrogen content, provided that the presence of hydrogen is not associated with the incorporation of porosity in the film.
SiC Power Devices – An Overview
Authors: Agarwal Anant , Das Mrinal , Krishnaswami Sumithra , Palmour John , Richmond James , Ryu Sei-Hyung 
Published: April 2011

ABSTRACTAn overview of SiC Power Devices is provided. Progress in 1200 V SiC Schottky diodes, 1200 V SiC BJTs, 10-20 kV SiC PiN diodes and 2 kV SiC Power MOSFETs will be described. SiC Schottky diodes have already been commercialized. The next step of inserting these diodes in Si IGBT modules is happening now. Emphasis is placed on the problems and issues at the SiC device/process interface which need to be urgently addressed such as the roughness created during the implant anneals, reliability of the gate oxide under positive and negative bias, low current gain of the BJTs, forward voltage instability in the pn junctions etc. Overcoming these issues in the near future will be critical to the successful commercialization of SiC devices.