bluuebunny/crossref_metadata_2025_split huggingface dataset:
First-Principles Study of Domain Evolution of IR on IR(111)
Authors: Habar M. , Ouannasser S. , Stauffer L. , Dreyssé H. , Wille L. T. 
Published: April 2011

ABSTRACTWe have calculated the effective cluster interactions (ECI) which govern the ordering of Ir adatoms on the Ir(111) surface. The computations are based on a tight-binding Hamiltonian in which no adjustable or experimentally determined parameters were introduced. Both atoms adsorbed in ‘bulk’ sites (i.e. continuing the fee lattice) and those in ‘surface’ sites (i.e. producing hep stacking) are considered. We use this formalism to determine the relative stability of various adsorption sites and cluster shapes at zero temperature. The overall trends are in excellent agreement with the experimental results found by Ehrlich and co-workers. Next, we employ these ECI in Monte Carlo simulations of the kinetics of domain growth and evolution. Specifically we analyze the effect of diffusion barriers and the competition between the ordering tendencies of the system and entropic effects. Typical ‘snapshots’ in a range of temperatures and coverages are discussed.
Double Periodicity Formation in EuTe/PbTe Superlattices
Authors: Shima M. , Salamanca-Riba L. , Springholz G. , Bauer G. 
Published: April 2011

ABSTRACTMolecular beam epitaxy was used to grow EuTe(x)/PbTe(y) short period superlattices with x=1-4 EuTe(111) monolayers alternating with y≈3x PbTe monolayers. The superlattices were characterized by transmission electron microscopy and high resolution x-ray diffraction. Regions with double periodicity were observed coexisting with areas of nominal periodicity. The sample with x=3.5 and y=9, for example, contains regions with double periodicity of x=7 and y=17. X-ray diffraction measurements confirm the formation of the double periodicity in these samples by the appearance of weak satellites in between the satellites of the nominal periodicity. The double periodicity in the superlattice is believed to result from interdiffusion during the growth. A model for this process is presented.
Structural Stability of CdSe Nanocrystallite Dispersions
Authors: Mattoussi H. , Murray C.B. , Bawendi M.G. , Ober R. 
Published: April 2011

AbstractX-ray scattering at small angles (SAXS) is used to study the structure and the thermodynamic properties of dispersions of CdSe nanocrystallite particles. In particular, this study allowed us to probe the inter particle interactions, and their dependence on several relevant parameters, such as the nature and size of the capping units attached to the crystallite surface and solvent.
Order-Disorder Transition Under Shearing : Application to Ball Milling
Authors: Pochet P. , Bellon P. , Chaffron L. , Martin G. 
Published: April 2011

AbstractThe evolution under sustained shear of an ordered crystal with B2 structure is studied by Monte-Carlo simulation: the effect of shearing is modelled by shifts of atomic planes, while thermally activated atomic diffusion is promoted by the motion of one vacancy. The tricritical point expected in the dynamical phase diagram from mean field theories and from Monte-Carlo simulations in the limit of weak driving (few atoms shifted at once) does not appear in such simulations, much in the same way as for "large cascade size" in alloys under irradiation. However an unexpected bifurcation in microstructures is observed which could be related to the order-disorder transition experimentally observed under ball-milling.
Structure and Properties of Novel Superhard Nanocrystalline/Amorphous Composite Materials
Authors: Vepřek S. , Haussmann M. , Reiprich S. 
Published: April 2011

AbstractWe have developed a theoretical concept for the design of novel superhard materials and verified it experimentally on several systems nc-MenN/a-Si3N4 (nc-MenN is a nanocrystalline transition metal nitride imbedded in a thin amorphous Si3N4 matrix). Hardness in excess of 5000 kg/mm2 (about 50 GPa) and elastic modulus of ≥550 GPa have been achieved [1-3]. Here we address the questions of the universality of the concept for the design of a variety of nc/a systems and the upper limit of the hardness which may be achieved.
The Effects of Elevated Temperature Deformation on Nanocrystalline Titanium-Aluminum
Authors: Kim Lisa S. , Klassen Thomas , Altstetter Carl J. , Averback Robert S. 
Published: April 2011

AbstractNanocrystalline titanium aluminum powder, of composition Ti-48Al, was synthesized using a Fritsch planetary ball mill with a grain size of approximately 10nm. The powder was compacted into cylindrical specimens with a relative density of 79% and subjected to uniaxial compressive loading at 600°C in a mechanical testing machine. From these results, the deformation of nanocrystalline titanium aluminum is examined with relation to the applied load and the resulting grain structure. The results suggest a grain refining mechanism occurring during the deformation process.
Magnetic Behavior of Ultrathin Films of Pseudomorphic Binary Alloys
Authors: Wu S.Z. , Schumann F.O. , Mankey G.J. , Willis R.F. 
Published: April 2011

AbstractIn this work we compare the ferromagnetic behavior of ultrathin FexNi(1-x) and CoxNi(1-x) films grown on Cu(100) epitaxially with varying stoichiometry. The thickness regime chosen was 1 to 5 ML over a wide range of alloy composition. Using a finite-size scaling law we proposed for the Curie temperature vs. film thickness measurements, we extrapolate and plot the bulk fee Curie temperature as a function of composition. The results suggest that the growth of these films is pseudomorphic with the films adapting a fee structure and the Cu lattice constant. Besides, the Invar effect is not observed in these ultrathin films of FexNi(1-x) alloys and the magnetic phase of Fe atoms is the low-spin ferromagnetic phase. The CoxNi(1-x) films show the expected monotonic decrease in Tc with increasing Ni content.
Preparation of Fe/SiO2 films by sputtering and their magnetic properties.
Authors: Akai Tomoko , Tabuchi Mitsuharu , Funahashi Ryoji , Yamanaka Hiroshi 
Published: April 2011

AbstractSiO2 thin films containing fine Fe particles were prepared by a co-sputtering method. α-Fe particles were then formed by heat-treating the film at 650°C to 700°C. The average size of the particles was controlled by changing heat-treatment time and temperature. The magnetic properties of these samples were investigated and discussed in terms of the size of the particles. It was found that the coercivity of the sample containing α-Fe particles (average particle size = 24nm) is as large as 36 Oe which is much higher than that of the bulk Fe.
Synthesis and Characterization of Nanostructured M50 Steel
Authors: Gonsalves K. E. , Rangarajan S. P. , Garcia-ruiz A. , Law C. C. 
Published: April 2011

AbstractThe synthesis of nanostructured multicomponent (Fe-Mo-Cr-V-C) M50 type steel has been carried out by two chemical routes: the sonochemical decomposition of organometallic precursors and the co-reduction of the respective metal halides. Both methods produce amorphous nanopowders, but the co-reduction method requires an additional heat treatment in vacuum at 700 °C to remove the by-product LiCl. In this paper we describe the synthetic methods and the characterization of the powders by XRD and SEM-EDAX. The powders exhibit a composition very close to that of M50 steel with an average grain size in the nanometer regime. In both cases the powders have been compacted in a vacuum hot press after they were heat treated in hydrogen. The characterization of the compacted specimens by XRD and SEM-EDAX is also discussed. The TEM characterization is presented for the sonochemically produced powders and compacts. A similar characterization of the co-reduced powders and the compacts is in progress. The consolidated specimens are homogeneous and dense, with an average grain size of ∼30 nm. Their hardness is higher as compared with that of the conventional M50 alloy.
Ti-Interlayer Mediated Epitaxy of CoSi2 with Ti Capping
Authors: Tung R. T. , Schrey F. 
Published: April 2011

AbstractThe growth of CoSi2 layers on Si(100) by Ti-interlayer mediated epitaxy (TIME) was studied. The use of a thin (1–3nm) Ti cap, the choice of an appropriate interlayer, and the removal of a metastable reaction by-product were found important for the fabrication of uniform CoSi2 layers. High quality, pinhole-free, single crystal [100]-oriented CoSi2 layers were fabricated. Multiply-oriented formation on heavily arsenic doped Si, void formation near oxide edges, and other salicide-related issues are also discussed.
Manufacturability Issues for Application of Silicides In 0.25 μm CMOS Process and Beyond
Authors: Wang Q. F. , Lauwers A. , Jonckx F. , de Potter M. , Chen Chun-Cho , Maex K. 
Published: April 2011

AbstractKey issues associated with the self-aligned silicide technology, such as formation of silicides on narrow poly gate, shallow silicided junction formation, gate to source/drain bridging, and interface contact resistance, are discussed. The comparison of important technological aspects for TiSi2 and CoSi2 is presented. The emphasis of this work is focused on the CoSi2 salicide technology with different variations, namely conventional process, Co/Ti capping process, and Ti/Co process. Based on the experimental results, CoSi2 should be considered as an attractive alternative to TiSi2 for the applications in sub-0.25 μm ULSI integrated circuits.
Kinetics of the C49 TO C54 Phase Transformation in TiSi2 thin Films on Deep-Sub-Micron Lines
Authors: Kittl J. A. , Prinslow D. A. , Apte P. P , Pas M. F. 
Published: April 2011

AbstractThe kinetics of the TiSi2 C49 to C54 phase transformation in thin films on patterned deepsub- micron lines, were studied to obtain the full time, temperature and linewidth dependence of the fraction transformed during rapid thermal annealing. A Johnson-Mehl-Avrami kinetic analysis was performed, obtaining Avrami exponents of 0.8±0.2 for all sub-micron lines and 1. 9±0.2 for a 40 μm side square structure, indicating heterogeneous nucleation followed by one dimensional growth for the narrow lines, and two dimensional growth for the square structure. The activation energy, of 3.9 eV, was independent of linewidth in the sub-micron range. Transformation times increased dramatically for decreasing linewidth, as the linewidth approached the grain size of the starting C49 phase. A kinetic model based on the density of nucleation sites as a function of linewidth and C49 grain size is proposed and shown to fit the data, for samples with two different C49 grain sizes.
Study on Ti-SiO2 Reaction - Thermodynamic Approach
Authors: Fontes M. B. A. , Capocchi J. D. T. , Acquadro J. C. 
Published: April 2011

AbstractInteractions between Ti and SiO2 thin films have been studied in self-aligned transistor process in the MOS Integrated Circuits Technology. A thermodynamic study of this interaction was conducted on the titanium and silicon dioxide chemistry. The Gibbs free energy was analyzed in the 25 to 1000°C range and it was concluded that the 11/3 Ti + SiO2 --> 1/3 Ti5 Si3 + 2 Ti reaction has the lowest free energy. Ti thin films were deposited by sputtering over dry silicon oxide and then sintered in atmospheric pressure furnace - RTP at argon ambient. The samples were analyzed by X-RAY Diffraction (XRD), Rutherford Backscatering Spectroscopy (RBS) and fourpoint- probe resistivity measurements. It was showed that experimental results can be modeled by theoretical analysis.
A Kinetic Study of the C49 to C54 Conversion in TiSi2 Using Electrical Resistivity Measurements on Single Sub-Micron Lines
Authors: Saenger K. L. , Cabral C. , Clevenger L. A. , Roy R. A. 
Published: April 2011

AbstractA simple, quasi-in situ resistivity technique was used to examine the C49 to C54 conversion kinetics of TiSi2 on sub-micron (0.2 to 1.1 μm) line structures formed in a self-aligned silicide (salicide) process. This technique was used to examine both aggregate conversion vs. time behavior and individual-line conversion vs. time behavior as a function of linewidth and polysilicon doping. As linewidth decreased, aggregate conversion vs. time at temperature behavior slowed, and the conversion behaviors shown by nominally identical lines became more variable. Four line behaviors were identified on the narrowest lines: short incubation/prompt conversion, gradual conversion, incomplete conversion, and no conversion. These behaviors are compared to those predicted by the Avrami equation, and to those predicted for a nucleation-site-density controlled reaction under conditions of low nucleation density. It is suggested that C49-C54 conversion in narrow lines may be primarily limited not by the number of C54 nucleation events, but by the presence of randomly occurring line-edge “defect” sites which slow and/or halt C54 grain growth.
Transport and Low Temperature Specific Heat Measurements of CrSi2 Single Crystals
Authors: Lasjaunias J. C. , Gottlieb U. , Laborde O. , Thomas O. , Madar R. 
Published: April 2011

AbstractWe have measured the Hall coefficient and the resistivity of single crystals of CrSi2. This compound crystallises in the hexagonal C40 structure and is generally reported as a semiconductor with a gap of around 0.35 eV. The resistivity is large, several hundreds of μΩ.cm and exhibits a metallic behaviour. RH leads to a hole concentration of 8.5×1026 m−3 at 300K.The specific heat at low temperature (0.7 K < T < 8 K ) can be describe as the sum of an electronic (γΓ) and a phonon (βT3) contribution. The analysis of the data leads to θD = 556 K and to an electronic density of states which is only two times smaller than those obtained for the metallic parent compounds VSi2, NbSi2 and TaSi2. This result questions the semiconducting nature of the chromium disilicide.
Characterization of Zirconium Germanosilicide Formed by Solid State Reaction of ZR With Sil−xGex Alloys
Authors: Wang Z. , Aldrich D. B. , Goeller P. , Nemanich R. J. , Sayers D. E. 
Published: April 2011

AbstractWe have investigated the electrical and structural properties of zirconium germanosilicide (Zr-Si-Ge) films formed during the Zr-Sil−xGex solid state reaction. Thin films of C49 Zr(Si1−xGex)2 were formed from the solid phase reaction of Zr and Si1−xGex bilayer structures. It was observed that Zr reacts uniformly with the Sil−xGex alloy and that C49 Zr(Si1−x Gex)2 is the final phase of the Zr-Si1−xGex, solid phase reaction (such tht y = x) for all compositions examined (x = 0.20, 0.33, and 0.50). The sheet resistance of the Zr(Si1−xGex)2 thin films were higher than the sheet resistance measured for ZrSi2 films. The stability of Zr(Sil−x Gex)2 in contact with Si1−Gex was investigated and no germanium segregation was detected in the Zr(Si1−xGex)2/Si1−Gex structures.
Growth and Electrical Performance of Heterojunction P+ Si1−x−yGexCy/p+ Si Diodes
Authors: Chang C. L. , Amour A. St. , Lanzerotti L. D. , Sturm J. C. 
Published: April 2011

AbstractWe have fabricated heterojunction p+ Si1−x−yGexCy/ p+ Si diodes. The SiGeC layers were grown epitaxially on Si (100) substrates by the rapid thermal chemical vapor deposition (RTCVD) technique using methysilane gas as a carbon precursor. The germanium concentration is 20% in these SiGeC alloys and the carbon concentrations are in the range of 0% to 1%. By studying the current-voltage characteristics of these diodes as a function of temperature the valence band discontinuities between SiGeC and Si layers were obtained as a function of carbon concentrations. We have found that the valence band discontinuity of the SiGe/Si heterostructure decreases by II meV when 1% of carbon is incorporated. Photoluminescence (PL) results show that 1% carbon increases the bandgap of strained p+SiGe alloys by 25 meV. This would imply that the conduction band discontinuity of SiGe/Si will decrease by 14 meV when 1% carbon is incorporated.
Effect of Phonon Confinement on Intersubband Lasing Lifetimes of Si/SiGe Quantum Well Structures
Authors: Friedman L. , Sun G. 
Published: April 2011

AbstractThe feasibility of population inversion is studied for the Si/SiGe system. Because of the absence of polar optical phonon scattering, the lifetime difference of the upper and lower lasing levels, to which the population inversion and laser gain are proportional, are an order of magnitude larger than in the III-Vs; nor does this show the large decrease to negative values (loss of population inversion) when the intersuband energy difference exceeds the optical phonon energy. We have investigated the effect of phonon confinement of the Ge-Ge and Si-Ge vibrations on the intersubband scattering rates and find a furthur enhancement of the the intersubband lifetimes as compared to those due to unconfined phonons.
Diffusion of Arsenic in Single Crystalline CoSi2
Authors: Pisch A. , Cardenas J. , Svensson B. G. , Petersson C. S. 
Published: April 2011

AbstractThe lattice diffusion of arsenic in CoSi2 has been studied in the temperature range from 750°C to 950°C. Two types of bulk samples were used: single crystals prepared by a modified Czochralski pulling technique from a radio frequency levitated melt and polycrystals synthesised by quenching from the melt. The latter samples were subsequently annealed in vacuum at 900°C and displayed grain sizes in the millimetre range. Starting from an ion implanted arsenic profile with two different doses (5·1014 and 5·1015 cm−2) the concentration versus depth profiles after annealing at different temperatures and different times were measured using secondary ion mass spectrometry (SIMS). Contrary to previous studies by other authors substantial diffusion has been observed with an activation energy of 3.3 eV and a pre-exponential factor of 7.37 cm2/s for the diffusion coefficient. These values are very close to the self diffusion coefficient of Si in CoSi2 suggesting that the As atoms migrate via thermal vacancies on nearest neighbour lattice sites by a similar type of mechanism as the Si (and Co) atoms. In the high dose implanted polycrystalline samples arsenic precipitation occurred which gives an estimate for the solid solubility in the 1019 atoms/cm3 range at 800 °C.
Phase Transformation of Titanium Disilicide Induced by High-Temperature Sputtering
Authors: Fujii K. , Tung R. T. , Eaglesham D. J. , Kikuta K. , Kikkawa T. 
Published: April 2011

AbstractThe reaction between sputtered Ti thin films and heavily arsenic doped Si(100) is studied. The use of an arsenic implantation to pre-amorphize the Si substrate and the choice of the substrate temperature during Ti sputtering are both found to have a significant effect on subsequent TiSi2 reactions. Cross-sectional transmission electron microscopy reveals that an amorphous TiSix layer is formed at the interface between Si and as-sputtered Ti. The thickness of this interfacial layer increases with the sputtering temperature. After rapid thermal anneals in nitrogen, the sheet resistances of TiSi2 thin films grown with the pre-amorphization step and a high sputtering temperature (450°C) are generally lower than films processed under other conditions. This apparent reduction in the temperature for the polymorphic C49 to 54 phase transformation in TiSi2 is shown to originate from a higher nucleation density of the C54-TiSi2 phase. These dependencies of the silicide reaction are ascribed to the interfacial amorphous TiSix layer. In increasing the nucleation density of the C54-TiSi2 phase, the amorphous TiSix layer is speculated to either act as a direct nucleation source for the C54-TiSi2 phase, or lead to more defective C49-TiSi2 structures which facilitate the C54-TiSi2 nucleation.
Grain Orientation Mapping and Spatially Resolved Strain Measurements for Polycrystalline Films by X-Ray Microdiffraction
Authors: Wang P.-C. , Cargill G. S. , Noyan I. C. , Liniger E. G. 
Published: April 2011

AbstractWe describe spatially resolved grain orientation mapping of polycrystalline films using a synchrotron-based x-ray microdiffraction system. The system consists of a tapered glass capillary as a white x-ray concentrator, an energy-dispersive solid state detector and an x-y-z sample stage. Two mapping modes are discussed: reciprocal-space mapping and real-space mapping. Information about the orientations of grains within the irradiated volume is determined by reciprocal-space mapping. The locations of grains having a specified orientation are determined by real-space mapping. Examples are shown for blanket films of AI(4 wt.% Cu) 4μm-thick and 0.5μm thick. Results are also shown for 10μm-wide and μm-wide pure lines. X-ray beams of 10inm diameter were used for these measurements. Spatially resolved thermal strain measurements were made for a single 10μm-wide, 200μm-long passivated Al line, and they were found to be consistent with calculations based on equi-biaxial thermal stress within the line.
Effect of Substrate Heating During Excimer Laser Annealing on Poly-Si TFT
Authors: Noguchi T. , Tang A. J. , Tsai J. A. , Reif R. 
Published: April 2011

AbstractSingle-shot ELA was performed on 45nm-thick amorphous Si films. With an increase in pulse energy density, the cystallinity improved drastically for both samples without heating and with heating at 400°C. Correspondingly, the characteristics of TFT fabricated using a low temperature process improved distinctly. The threshold voltage decreased depending on the decrease in gate voltage swing due to the improvement in crystallinity of Si films. Efficient single-pulse ELA of less than 250MJ/cm2 as the optimum condition for poly Si TFT has been attained as a result of saving an energy amount of 100mJ/cm2 by heating the substrate. Moreover, a uniform distribution of TFT characteristics across the wafer was obtained.
Selective Deposition of Polycrystalline Silicon Thin Films by Hot-Wire CVD
Authors: Yu Shuangying , Gulari Erdogan , Kanicki Jerzy 
Published: April 2011

AbstractPolycrystalline silicon thin films have been selectively deposited at a deposition rate of 60–100Å/min and a substrate temperature of 300°C on molybdenum or silicon over silicon dioxide, silicon nitride or Coming 7059 glass substrate in a continuous hot-wire CVD process involving hydrogen and disilane. Excellent selectivity is achieved on features as small as one micrometer spaced molybdenum lines. The crystallinity of the selectively deposited polysilicon films is thickness dependent. The substrate selectivity is sensitive to both silicon content in the gas phase and substrate temperature. Selective deposition shifts to lower Si content in the gas phase when substrate temperature increases. At a certain substrate temperature, for a silicon content above a certain value in the gas phase, films with similar crystallinity are non-selectively deposited on both molybdenum and silicon dioxide.
Significance of Microstructure for a MOCVD-Grown YSZ Thin Film Gas Sensor
Authors: Vetrone J. , Foster C. , Bai G. 
Published: April 2011

AbstractWe report the fabrication and characterization of a low temperature (200°C-400°C) thin film gas sensor constructed from a MOCVD-grown yttria-stabilized zirconia (YSZ) layer sandwiched between two platinum thin film electrodes. A reproducible gas-sensing response is produced by applying a cyclic voltage which generates voltammograms with gas-specific current peaks and shapes. Growth conditions are optimized for preparing YSZ films having dense microstructures, low leakage currents, and maximum ion conductivities. In particular, the effect of growth temperature on film morphology and texture is discussed and related to the electrical and gas-sensing properties of the thin film sensor device.