bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Al on Quasicrystal Formation in Zr-Ti-Nb-Cu-Ni-Al Metallic Glasses
Authors: Scudino Sergio , Eckert Jürgen , Kühn Uta , Breitzke Hergen , Lüders Klaus , Schultz Ludwig 
Published: April 2011

ABSTRACTThe effect of Al on the crystallization behavior of (Zr0.616Ti0.087 Nb0.027Cu0.15Ni0.12)100−xAlx melt-spun glassy ribbons with x = 7.5, 5, 2.5 and 0 was investigated by differential scanning calorimetry, x-ray diffraction and transmission electron microscopy. The devitrification of the ribbons is characterized by the formation of a metastable quasicrystalline phase during the first stage of the crystallization process even for the alloy with x = 0. Therefore, Al is not essential for quasicrystal formation in the present alloys. However, it affects the properties of the amorphous as well as of the quasicrystalline phase. With decreasing Al content, the temperature range of stability of the quasicrystalline phase increases whereas the thermal stability of the amorphous phase decreases together with a slight decrease of the extension of the supercooled liquid region. Thus, it is concluded that although the addition of Al improves the stability of the glassy phase, it has no beneficial effect on the formation of quasicrystals.
Metastable States During Devitrification of a Zr70Pd20Cu10 Metallic Glass
Authors: Kramer M. J. , Sordelet D. J. 
Published: April 2011

ABSTRACTHigh energy synchrotron x-rays (124.63 keV) are used to investigate the initial stages of the devitrification for the Zr70Pd20Cu10 metallic glass prepared by melt-spinning (MS). Due to the excellent signal:noise, we are able to determine the initial nucleating phase by analyzing the differences in the total scattering function S (Q) as a function of time at a temperature ∼ 50 K below the crystallization temperature. The alloy undergoes a structural relaxation prior to nucleation and growth. Devitrification proceeds from nucleation of the icosahedral phase. The differential pair distribution function (dPDF) indicates that the as-quenched alloy may have icosahedral-like order which undergoes local rearrangement to true icosahedral order at an annealing temperature 50 K below the crystallization temperature. More importantly, time-resolved high-energy synchrotron is shown to have excellent sensitivity to the initial atomic rearrangements preceding nucleation in metallic glasses.
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.
Enthalpy Relaxation Kinetics of the Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 Supercooled Liquid Close to the Glass Transition
Authors: Shah Minalben B. , Busch Ralf 
Published: April 2011

ABSTRACTIsothermal relaxation studies of the Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 bulk metallic glass forming alloy were performed using Differential Scanning Calorimetry in the glass transition and the supercooled liquid region. A new experimental method was developed to study the isothermal enthalpy relaxation kinetics. The results reveal that the enthalpy relaxes in an Arrhenius fashion. The activation energy obtained from the Arrhenius fit is comparable to the activation energy required for the diffusion of the medium size atoms. This suggests that the solid-state diffusion governs the enthalpy relaxation process. The stretching exponents for the relaxation are close to unity, which indicates that the alloy is a rather strong glass former.
Synchrotron Strain Measurements for in situ Formed Metallic Glass Matrix Composites
Authors: Ott R. T. , Sansoz F. , Molinari J. F. , Almer J. , Fan C. , Hufnagel T. C. 
Published: April 2011

ABSTRACTWe have examined the micromechanical behavior of in situ formed metallic glass composites by performing in situ high-energy synchrotron X-ray scattering during uniaxial compression. The load partitioning between the amorphous matrix and the reinforcing particles was examined by measuring the lattice strains in the crystalline particles during compressive loading. The crystalline particles yield in compression during loading followed by tensile yielding during unloading. The large elastic mismatch between the two phases leads to large residual strains after each loading cycle. The load partitioning was also examined with finite element modeling (FEM). The predicted von Mises effective stress in the crystalline particles from the FEM calculations compares well with the experimentally determined von Mises effective stress so long as the deformation is elastic in both particles and matrix. After the particles yield, the model predicts strain hardening of the particles that is not observed experimentally.
Heating and Structural Disordering Effects of the Nonlinear Viscous Flow in a Zr55Al10Ni5Cu30 Bulk Metallic Glass
Authors: Kato Hidemi , Inoue Akihisa , Chen H. S. 
Published: April 2011

ABSTRACTHeat evolution of stress-induced structural disorder,ΔHs(ε), of a Zr55Al10Ni5Cu30bulk metallic glass (BMG) during constant ram-velocity deformation at the glass transition region (Tg= 680 K) was deduced from in-situ measurements of temperature change of the deforming sample. At the transition from the linear to nonlinear viscoelasticity, the behavior of viscosity change with strain, η(ε), is qualitatively consistent with the enthalpy evolution of the structural disordering,ΔHs(ε), but not with the temperature change, ΔT(ε). It is concluded that the initial softening deformation is due to the stress-induced structural disordering. The change in the nonlinearity, -log ñ ≡ −logη/ηN, is found to be proportional to theΔHsand the slope ofΔHs(–logñ) can be estimated to ∼ 400 J/mol, whereηNis the Newtonian viscosity. On the other hand, the temperature raise,ΔT(ε), is pronouncedly delayed as compared with theη(ε) andΔHs(ε) at the transition, but is determined by the product of stress and plastic strain-rate,σ·εp, and is nearly proportional to it at the steady-state. The slope ofΔT(σ·εp) can be estimated to 5.2×10-2K mol/W.
Strained Si-on-Insulator Fabricated from Elastically-Relaxed Si/SiGe Structures
Authors: Mooney P.M. , Cohen G.M. , Chen H. , Chu J.O. , Klymko N. 
Published: April 2011

ABSTRACTBlanket pseudomorphic Si0.8Ge0.2/Si layer structures grown by Rapid thermal Chemical Vapor Deposition (RTCVD) on SOI substrates were etched to form 5μm × 5μm slabs, supported by a single pedestal at the center. Symmetric tri-layer slabs, 20nm Si/236nm Si0.8Ge0.2/20nm Si supported by a SiO2 pedestal are flat and x-ray diffraction measurements of the strain and the thickness of the layers confirmed that the strain is shared between the Si and SiGe layers according to the ratio of the thickness of the SiGe and Si layers. These tri-layer structures were then firmly attached to the substrate using a filling material. A thermal oxide layer was grown on the upper and lower surface of the free-standing structures and then polycrystalline Si was deposited to fill the space between the free-standing structure and the Si substrate, thus attaching the bottom strained Si layer to the substrate. The polycrystalline Si was subsequently removed by reactive ion etching except from under the /SiGe/Si slab. The top SiO2 and Si layers as well as the SiGe layer were then removed selectively by wet etching. Raman spectroscopy measurements show that the strain in the attached strained Si-on-insulator layer is ε = 0.0067.
Reduced Pressure - Chemical Vapor Deposition of high Ge content (20% - 55%) SiGe virtual substrates
Authors: Bogumilowicz Y. , Hartmann J.M. , Laugier F. , Rolland G. , Billon T. , Renard V. , Olshanetsky E.B. , Estibals O. , Kvon Z.D. , Portal J.C. 
Published: April 2011

ABSTRACTWe have studied the strain state, film and surface morphology of SiGe virtual substrates (Ge concentrations in-between 20% and 55%) grown by reduced pressure – chemical vapor deposition. The macroscopic degree of strain relaxation of those virtual substrates is equal to 97.2 ± 1.5%. The misfit dislocations generated to relax the lattice mismatch between Si and SiGe are mostly confined inside the graded layer. Indeed, the threading dislocations density obtained for Ge concentrations of 20% and 26% is indeed typically of the order of 7.5 ± 2.5 105 cm−2. Low surface root mean square roughness have been obtained, with values in-between 2 and 5 nm. In order to check the electronic quality of our layers, we have grown a MODFET-like heterostructure, with a buried tensile-strained Si channel 8 nm thick embedded inside SiGe 26%. We have obtained a well-behaved 2-dimensional electron gas in the Si channel, with electron sheet densities and mobilities at 1.45K of 5.4×1011 cm−2 and 212 000 cm2 V−1 s−1, respectively.
SiGe-on-Insulator and Ge-on-Insulator Substrates Fabricated by Ge-Condensation Technique for High-Mobility Channel CMOS Devices
Authors: Tezuka Tsutomu , Mizuno Tomohisa , Sugiyama Naoharu , Nakaharai Shu , Moriyama Yoshihiko , Usuda Koji , Numata Toshinori , Hirashita Norio , Maeda Tatsuro , Takagi Shin-ichi , Miyamura Yoshiji , Toyoda Eiji 
Published: April 2011

ABSTRACTA new fabrication method of SiGe-on-Insulator (SGOI) and Ge-on-Insulator (GOI) structures are presented as well as the application to high-mobility channel CMOS devices. This method, the Ge-condensation technique, consists of epitaxial growth of a SiGe layer with a low Ge fraction on an SOI substrate and successive oxidation at high temperatures, which can be incorporated in conventional CMOS processes. During the oxidation, Ge atoms are pushed out from the oxide layer and condensed in the remaining SiGe layer. The interface between the Si and SiGe layers is disappeared due to the interdiffusion of Si and Ge atoms. Eventually, an SGOI layer with a higher Ge fraction is formed on the buried oxide layer. The Ge fraction in the SGOI layer can be controlled by the oxidation time because total amount of Ge atoms in the SGOI layer is conserved throughout the oxidation process. We found that the lattice relaxation in the SGOI layer also can be controlled through the initial SiGe thickness. P- and n-type strained SOI MOSFETs, which were fabricated on relaxed SGOI substrates formed by this technique, exhibited mobility enhancement of 50% and 80%, respectively. CMOS ring oscillators comprised of the MOSFETs exhibited reduction in propagation delay of 70%-30% compared to a conventional SOI-CMOS device. Ultrathin-body strained SGOI pMOSFETs with high Ge fraction and surface channels were also fabricated by this technique. These devices exhibited hole-mobility enhancement factors up to 2.3. Furthermore, Ge-on-Insulator (GOI) structures with thicknesses less than 10 nm were realized for ultrathin body GOI-CMOS applications by using the Ge-condensation technique. In conclusion, the Ge-condensation technique is a promising technique for fabricating various types of high-mobility channel-on-insulator devices.
Germanium-On-Insulator (GeOI) structure realized by the Smart Cut™ technology
Authors: Letertre F. , Deguet C. , Richtarch C. , Faure B. , Hartmann JM , Chieu F. , Beaumont A. , Dechamp J. , Morales C. , Allibert F. , Perreau P. , Pocas S. , Personnic S. , Lagahe-Blanchard C. , Ghyselen B. , Vaillant YM Le , Jalaguier  , Kernevez N. , Mazure C. 
Published: April 2011

ABSTRACTFirst results on formation of thin film GeOI structures by the Smart Cut™ technology are presented in this paper. Thin single crystal layers of Ge have been successfully transferred, via oxide bonding layer, onto standard Si substrates with diameters ranging from 100 to 200 mm. Compared to SOI manufacturing, the development of GeOI requires adaptation to the available germanium material, since the starting material can be either bulk Ge or an epitaxial layer. Some results will be presented for GeOI formation according to the different technological options. Germanium splitting kinetics will be discussed and compared to already published results. To show good quality of the GeOI structures, detailed characterization has been done by TEM cross sections for defect densities, interfaces abruptness and layers homogeneities evaluation. AFM was used for surface roughness measurements. These results help define procedures that are required to achieve large diameter high quality GeOI structures.
High-Performance SiGe MODFET Technology
Authors: Koester S. J. , Chu J. O. , Saenger K. L. , Ouyang Q. C. , Ott J.A. , Canaperi D. F. , Tornello J. A. , Jahnes C.V. , Steen S. E. 
Published: April 2011

ABSTRACTAn overview of SiGe modulation-doped field-effect transistor (MODFET) technology is provided. The layer structures and mobility enhancements for both p- and n-channel modulation-doped quantum wells are described and compared to mobilities in Si/SiO2 inversion layers. Next, previous results on high-performance n- and p-MODFETs fabricated at IBM and elsewhere are reviewed, followed by recent results on laterally-scaled Si/SiGe n-MODFETs with gate lengths as small as 70 nm. We conclude with a discussion of the materials issues for the future vertical and lateral scaling of SiGe MODFETs.
Atomic Force Microscopy Study of Conformal Sputtering in Strained Silicon Samples
Authors: Chao Kuo-Jen , Goodman Gary 
Published: April 2011

ABSTRACTPrecise determination of the Ge outdiffusion into the Si cap in strained Si/SiGe structures and the depth distribution of dopants have been critical to the industry and a challenge to the SIMS community. Will the rough cross-hatch surface topography degrade the SIMS depth resolution, or alter the accuracy of the depth profile?Here we report on a novel AFM approach to show that the SIMS measurement process results in conformal sputtering. Therefore, maintaining excellent depth resolution and the depth distribution accuracy capabilities of SIMS for these material systems.
Characterization of Structural Quality of Bonded Silicon-On-Insulator Wafers by Spectroscopic Ellipsometry and Raman Spectroscopy
Authors: Nguyen N. V. , Maslar J. E. , Kim Jin-Yong , Han Jin-Ping , Park Jin-Won , Chandler-Horowitz D. , Vogel E. M. 
Published: April 2011

ABSTRACTThe crystalline quality of bonded Silicon-On-Insulator (SOI) wafers were examined by spectroscopic ellipsometry and Raman spectroscopy. Both techniques detect slight structural defects in the SOI layer. If a pure crystalline silicon dielectric function is assumed for the SOI layer, the spectroscopic ellipsometry data fitting yields an unacceptably large discrepancy between the experimental and modeled data. The best fits for all the samples result in a dielectric function of the SOI layer that consists of a physical mixture of crystalline silicon and about 4 % to 7 % of amorphous silicon. Using such a mixture indicates that there are still some defects in the SOI layer when compared with the high-quality bulk crystalline silicon. This observation is further supported by Raman spectroscopy measurements. The Raman spectra of all SOI samples exhibit a feature at about 495 cm−1 that is not observed in the crystalline silicon spectrum. Features similar to the 495 cm−1 feature have been reported in the literature and attributed to dislocations or faults in the silicon lattice.
Relaxation of Strained SiGe on Insulator by Direct Wafer Bonding
Authors: Maa Jer-shen , Lee Jong-Jan , Tweet Douglas , Hsu Sheng Teng 
Published: April 2011

ABSTRACTStrained SiGe was bonded to silicon dioxide by direct wafer bonding and Smart-cut technique. Strained SiGe with a graded 20%-30% Ge concentration was deposited by RTCVD on (100) Si to a thickness between 300nm to 350nm. H2+ for wafer splitting was implanted at an energy varied from 40 keV to 150 keV and a dose between 2.5E16 and 4.5E16 ions/cm2. SiGe relaxation was found to depend on wafer split temperature, and on post-split annealing temperature. SiGe relaxation of greater than 80% was observed after wafer splitting and annealing. Was it from gliding of a SiGe film weakly bonded to an oxide surface? In order to determine the relaxation mechanism, samples with different film structure were prepared. The films were then annealed at various temperatures. Some film showed a high degree of relaxation, and some showed minimal relaxation, depending mostly on hydrogen implant depth. The results indicated that the generation of dislocation is the possible cause of SiGe relaxation.
Effect of Point Defect Injection on B diffusion in C containing Si and SiGe
Authors: Karunaratne Mudith S. A. , Bonar Janet M. , Zhang Jing , Willoughby Arthur F. W. 
Published: April 2011

ABSTRACTIn this paper, we compare B diffusion in epitaxial Si, Si with 0.1%C, SiGe with 11% Ge and SiGe:C with 11%Ge and 0.1%C at 1000°C under interstitial, vacancy and non-injection annealing conditions. Diffusion coefficients of B in each material were extracted by computer simulation, using secondary ion mass spectroscopy (SIMS) profiles obtained from samples before and after annealing.Interstitial injection enhances B diffusion considerably in all materials compared to inert annealing. In samples which experienced vacancy injection, B diffusion was suppressed. The results are consistent with the view that B diffusion in these materials occurs primarily via interstitialcy type defects.
Bulk-like ferroelectric and piezoeletric properties of transferred-BaTiO3 single crystal thin films
Authors: Park Young-Bae , Ruglovsky Jennifer L. , Dicken Matthew J. , Atwater Harry A. , Watson Thomas J. 
Published: April 2011

ABSTRACTLayer transfer of thin BaTiO3 films onto silicon-based substrates has been investigated. H+ and He+ ion implantation created a buried sacrificial layer in the BaTiO3 single crystals. Thermodynamics and kinetics of cavity nucleation and growth at the bonding interface have been investigated and single crystal thin film layers were transferred onto amorphous Si3N4 and Pt substrates. We have found that defects generated by ion implantation in ferroelectric materials can be significantly recovered with the subsequent annealing for layer splitting. Also, after high dose ion implantation, the films remain single crystal and stoichiometry. Finally, characterization proves the layer-transferred thin films are ferroelectrically active, with domains and piezoresponse similar to bulk crystals.
Comparison of Sol-Gel Derived and Pulsed Laser Deposited Epitaxial La0.67Ca0.33MnO3 Films for IR Bolometer
Authors: Fors Rickard , Pohl Annika , Khartsev Sergey , Grishin Alexander , Westin Gunnar 
Published: April 2011

ABSTRACTEpitaxial La0.67Ca0.33MnO3 films have been prepared on LaAlO3 crystals by pulsed laser deposition (PLD) and by a novel all-alkoxide sol-gel technique. Different out-of-plane lattice parameters are found for the as-prepared films, and scanning electron microscopy shows a more porous structure for sol-gel films as compared to PLD films. These differences are largely removed by post-annealing at 1000 °C. Transport measurements show maximum temperature coefficient of resistivity of 8.2 % K−1 at 258 K (PLD) and 6.1 % K−1 at 241 K (sol-gel) and colossal magnetoresistance at 7 kOe of 35 % at 263 K (PLD) and 32 % at 246 K (sol-gel).
Carrier transport of extended and localized states in InGaO3(ZnO)5
Authors: Nomura Kenji , Ohta Hiromichi , Ueda Kazushige , Kamiya Toshio , Hirano Masahiro , Hosono Hideo 
Published: April 2011

ABSTRACTCarrier transport properties and electronic structure of an n-type transparent oxide semiconductor, InGaO3(ZnO)5, were investigated using single-crystalline thin films. Room-temperature Hall mobility strongly depends on carrier concentration, and rapidly increased from ∼ 2 cm2(Vs)-1 to > 10 cm2(Vs)-1 around the carrier concentration (Nth ∼3 × 1018 cm−3. This change is associatedwith insulator-metal transition. These results are explained by a model similar to Anderson localization, in which shallow semi-localized states are formed originating from random distribution of Ga3+ and Zn2+ ions in the intrinsic crystal structure of InGaO3(ZnO)5. The present conclusion suggests that electron densities larger than Nth are necessary to attain high performances in drift carrier devices fabricated using InGaO3(ZnO)5. It was demonstrated that transparent filed-effect transistors exhibited good performances such as a “normally-offcharacteristics”, an on/off current ratios as large as 105 and a field-effect mobility ∼80 cm2(Vs)-1when high-k material, amorphous HfOx, was used as a gate insulator.
Structural and Electrical Properties of Ba0.5Sr0.5TiO3 Thin Films for Tunable Microwave Applications
Authors: Manavalan Sriraj G. , Kumar Ashok , Weller T. , Sikder A.K. 
Published: April 2011

ABSTRACTThe primary objective of this research is to optimize the different deposition conditions to obtain high tunability and low dielectric loss of Barium Strontium Titanate (BST) thin films at microwave frequencies. Ba0.5Sr0.5TiO3thin films were deposited on Pt/TiO2/SiO2/Si substrates by pulsed laser deposition technique (PLD). Deposition conditions like temperature, oxygen pressure, substrate to target distance and laser energy are varied to obtain the objective. Deposition of the BST thin films on the Pt/TiO2/SiO2/Si substrates was carried out at temperatures of 450°°C, 550°°C, 650°°C and oxygen pressures of 250mTorr and 450mTorr with laser fluence of 250 mJ/cm2 and 450mJ/cm2 at 10 pulses per second. The microstructural and phase analysis of the deposited BST films at different temperatures and different oxygen pressures were performed using X-ray diffraction (XRD) method. The diffraction patterns are attributed to cubic (perovskite) crystal system. Atomic force microscopy (AFM) was used to perform the surface analysis of the films deposited at different substrate to target distances, varied laser energies and oxygen pressures. The BST capacitor was fabricated using the Coplanar Waveguide Structure and the capacitance and dielectric constant were measured using the Vector Network Analyzer (VNA). Tunability of 3.1:1 and loss tangent of 0.0121 was achieved at 0.4 – 0.8 GHz.