bluuebunny/crossref_metadata_2025_split huggingface dataset:
Large Scale Synthesis of Silicon Nanowires by Laser Ablation
Authors: Tang Y.H. , Zhang Y.F. , Lee C.S. , Wang N. , Yu D.P. , Bello I. , Lee S.T. 
Published: April 2011

AbstractQuasi one-dimensional materials have attracted considerable attention in recent years because of its potential to both fundamental physics and nanoelectronic applications. More recently, we have achieved large scale synthesis of silicon nanowires (SINW) at a high growth rate by laser ablation of Si target at 1200 °C. The laser source was a pulsed KrF excimer laser and the Si targets were made by pressing Si powder of 5 microns in size. 50 sccm Ar was used as a carrying gas flowing from the side near the Si target towards a water-cooled copper finger. Si nanowires have been grown with diameters ranging from 3 to 43 nm and several hundreds microns in length after 2 hours of laser ablation of Si target. The SLNWs were analyzed by XRD, Raman, EDS, TEM and HRTEM. Successful large scale synthesis of SINW by laser ablation extends the pulsed laser ablation method from depositing thin films to synthesis of nanowires.
Diffusion of Strain Induced Defects after Heavy Ion Irradiation
Authors: Aggarwal G. , Sen P. 
Published: April 2011

ABSTRACTWe report study of recovery dynamics, followed by in-situ resistivity measurement, after 100 MeV oxygen ion irradiation in cold rolled Fe at 300K. Scaling behavior with microstructural density and temperature of sample has been used to establish stress induced defects formed during irradiation as a new type of sink. The dynamics after irradiation has been shown to be due to migration of defects to two types of sinks i.e. stress induced defect as variable sinks and internal surfaces as fixed sinks.
The Volume Diffusion of Interstitial Atoms in Ordered Magnetic Alloys Under Pressure
Authors: Zaginaichenko S.Yu. , Matysina Z.A. 
Published: April 2011

ABSTRACTTheoretical investigation of interstitial atom diffusion in a binary alloy A-B with crystal lattice of CsCl type with atomic and magnetic (ferromagnetic or antiferromagnetic) order has been performed. The influence of external pressure on diffusion of hydrogen atoms has been defined. Calculations has been carried out by methods of statistical physics with application of thermodynamic functions.
Calculation of The Diffusion Parameters in an Ordered Ni3Al-Alloy for A Relaxed Lattice
Authors: Schmidt C. , Bocquet J.L. 
Published: April 2011

ABSTRACTUsing atomistic computer simulations, we calculate the diffusion parameters of an Ll2-ordered Ni3Al-alloy. A conjugate gradient algorithm under constant zero pressure and a semi-empirical N-body potential are applied to evaluate potential barrier heights and pre-exponential factors. We focus our investigation on those diffusion mechanisms that have been proposed to account for the experimentally observed but theoretically still disputed fast self-diffusion of Al in Ni3Al: antisite bridge mechanisms and correlated six-jump cycles. Our results demonstrate that the most competitive jumps or jump sequences involve AlNJ-antistructure atoms which are shown to play a key role in the diffusion process by either actively or passively lowering the activation energy of migration.
Monte Carlo Simulation of the Initial Disordering Rate of Cu3Au Under Ion Irradiation
Authors: Wei L.C. , Lang E. , Ghaly M. , Bellon P. , Averback R. S. 
Published: April 2011

ABSTRACTThe temperature dependence of disordering of Cu3Au during ion irradiation has been investigated by computer simulations using MONTE CARLO methods. The investigation was motivated by peculiar experimental observations that the initial disordering rate begins to decrease above ~300 K, which can be explained by vacancies just becoming mobile at that temperature, but then at ~ 475 K, it reaches a minimum and then increases rapidly as the temperature is further increased, up to the order-disorder temperature. The present simulation shows that this behavior can be understood in terms of temperatures dependencies in both atomic mixing in the cascade and the efficiency of vacancy annealing of disorder as the vacancies diffuse out of the cascade.
Stochastic Vacancy Motion in B2 Intermetallics Detected by PAC
Authors: Bai Bin , Collins Gary S. , Nieuwenhuis Harmen Thys , Wei Mingzhong , Evenson William E. 
Published: April 2011

ABSTRACTUsing perturbed angular correlation of gamma rays (PAC), nuclear relaxation has been detected at high temperature in highly ordered B2 intermetallics that is attributed to stochastic motion of vacancies near 111In/Cd probe atoms. The relaxation is of quadrupole interaction signals due to transition-metal vacancies in the first atomic shells of the probes. Possible relaxation mechanisms are reorientation of the vacancy with respect to the probe, detrapping of the vacancy, or trapping of a second vacancy. The relaxation reaches values of 10 MHz at temperatures of 1500K, 1200 K and 1170 K, respectively, for NiAI, FeAl and PdIn. For NiAl and FeAI, the onset of relaxation is abrupt, suggesting an activation enthalpy for the associated vacancy motion of several electron-volts. For PdIn, the relaxation has an activation enthalpy of 1.00(19) eV, a value significantly lower than might be expected naively on the basis of diffusion data. This difference gives insight into vacancy motion and diffusion mechanisms in PdIn.
Modeling of Diffusion in Ordered Structures of B2-Type
Authors: Ganchenkova M.G. , Nazarov A.V. 
Published: April 2011

ABSTRACTUsing Monte Carlo simulation, we model the effect of interaction of vacancies on their diffusivities in ordered structures of B2-type. The activation barriers of atom jumps to vacancy are calculated by the static relaxation technique using interatomic potentials for both vacancy exchanges: with nearest-neighbour atoms and next-nearest-neighbour atoms. This is done for all possible positions of the second vacancy. Knowing these barriers it is possible to calculate the jump rates and to model the vacancy migration. The calculations were done for a system with parameters similar to NiAl. The modeling allows to inter the existence of a new diffusion mechanism in ordered structures of B2-type, which could be attributable to dynamic pair of vacancies and vacancy exchanges with next-nearest-neighbor atoms.
Kinetics and Mechanisms of Intermetallic Growth by Bulk Interdiffusion
Authors: Paritskaya L.N. , Kaganovskii Yu.S. , Bogdanov V.V. 
Published: April 2011

ABSTRACTKinetic properties of γ-phase (Cu5Zn8) growth in the binary system Cu-Zn were studied at 160-270°C. It has been found that γ-phase grows in diffusional-kinetic regime. Both kinetic coefficients of interfacial reaction rate β and diffusion coefficients D have been determined taking into account Kirkendall effect. Arrhenius equations for the kinetic and diffusion coefficients have been obtained, with the high values of “dynamic” diffusion coefficients and low activation energies for both diffusion (QD) and interfacial reaction (Qβ). The mechanism of Zn diffusion in non-stoichiometric Cu5Zn8 phase is discussed.
Effect of Atomic Order on Iron and Cobalt Grain Boundary Diffusion in the FeCo Equiatomic Compound
Authors: Tôkei Zs. , Bernardini J. , Beke D. L. 
Published: April 2011

ABSTRACTSimultaneous grain boundary self-diffusion of iron and cobalt in FeCo was investigated in the B-kinetic regime by the radiotracer method combined with a serial sectioning technique over the temperature range 873-1133 K, which includes the A2-B2 bulk order-disorder transition temperature. This transition leads to a decrease in both iron and cobalt mass transport mainly owing to a change in the pre-exponential factor, but not in the diffusion activation energy. Moreover, the breaking point in the Arrhenius plots is observed below the bulk order-disorder transition temperature. In view of recent surface segregation studies on Fe-Co, and according to the Fe-Co phase diagram, the results are discussed assuming an iron segregation, which decreases the A2-B2 transition temperature in grain boundaries.
Out Diffusion of Oxygen in Czochralski Silicon at Low Temperatures
Authors: McQuaid S.A. , Johnson B.K. , Gambaro D. , Falster R. , Ashwin M. , Newman R.C. 
Published: April 2011

ABSTRACTPreviously reported measurements of anomalously high rates of oxygen out-diffusion in Czochralski silicon at low temperatures (T≤450°C) are confirmed. The surface concentration is shown to decrease with increasing time while the depth to which the concentration is depleted remains constant. Exposure to a hydrogen plasma under conditions known to catalyse the diffusion of isolated oxygen atoms causes an increased rate of decrease of the surface concentration without significantly affecting the depth to which the concentration is depleted. The evolution of the out-diffusion profiles cannot be explained by a catalytic mechanism operating on the isolated oxygen atoms. A slow conversion of Oi to a complex containing oxygen which can diffuse rapidly over long distances before being trapped either on the surface or in the bulk of the sample can account for both out-diffusion and simultaneous loss of [Oi] in the bulk. The conversion rate is enhanced by exposure to a hydrogen plasma, indicating that it is controlled by the diffusion rate of isolated atoms.
Threshold Character of Zn Diffusion into InP
Authors: Kamanin A.V. , Kudryavtsev Yu.A. , Shmidt N.M. 
Published: April 2011

ABSTRACTThe initial diffusion stage (lIDS) of Zn in InP from polymer spin-on films has been investigated. The threshold diffusion temperature of 375°C has been established. It has been found that the heavily-doped near-surface layer, that consisted of electrically neutral zinc-containing complexes, was formed at IDS, while a low part of Zn was electrically active. The Zn diffusivity during IDS has been found to be at least two orders of magnitude more than the Zn diffusivity obtained after an isothermal diffusion.
Quantitative Measurement of Reduction of Boron Diffusion by Substitutional Carbon Incorporation
Authors: Carroll M. S. , Lanzerotti L. D. , Sturm J. C. 
Published: April 2011

ABSTRACTRecently, the suppression of boron diffusion due to both thermal and transient enhanced diffusion (TED) has been demonstrated through the incorporation of 0.5% substitutional carbon in the base of Si/SiGe/Si heterojunction transistor's (HBT)[1,2]. Because the devices are sensitive to diffusion on a scale less than that we can detect with SIMS, in this paper combined process and device modeling (TMA TSUPREM4 and MEDICI) are used to relate observed electrical characteristics (collector saturation currents and Early voltages) of the HBT's to boron diffusion, with a sensitivity of 20-30Å. Boron diffusivity in the SiGeC base is ~8 times slower than that of the boron diffusivity in the SiGe base without implant damage (no TED). In the case of ion implant damage in an overlying layer to cause TED the excess interstitial concentration due to ion implant damage is reduced by approximately 99% through incorporation of 0.5% substitutional carbon in the HBT SiGe bases. This demonstrates that carbon incorporation acts as an effective sink for interstitials.
Molecular Diffusion Processes in Crystalline Microporous Materials
Authors: Sastre G. , Corma A. , Catlow C. R. A. 
Published: April 2011

ABSTRACTAtomistic Molecular Dynamics are used to simulate diffusion of hydrocarbons inside the microporous structure of siliceous zeolite CIT-I, with chemical composition SiO2. CIT-1 is a crystalline microporous material containing channels formed by rings containing 12 and 10 Si atoms (Figure 1). The dimensions of these two channel systems are sufficient to cause substantial differences in the diffusion of para-xylene and ortho-xylene. Diffusion coefficients as a function of loading of each isomer, and activation energies have been calculated from the simulations. The effect of the isomer size in the diffusion path is also analysed.
An Oxygen Potential Gradient as a Possible Diffusion Driving Force
Authors: Pint B. A. , Alexander K. B. , Monteiro O. R. , Brown I. G. 
Published: April 2011

ABSTRACTOxygen-active elements such as Y, Zr and Hf are added to alumina-forming alloys to improve the adhesion of the external α-Al2O3 scale formed during high temperature oxidation. During oxidation at 1000°-1500°C, many such elements are observed to diffuse from the alloy through the scale and form oxide particles at the scale-gas interface. Once nucleated, the volume fraction of these particles increases with oxidation temperature and time. The continued increase in volume fraction with time suggests that diffusion is not merely driven by a concentration gradient of the oxygen-active elements. Pre-coating with a dense, 1 μm-thick, plasma-deposited alumina layer prior to oxidation did not prevent the nucleation and growth of these types of particles at the gas interface of the coating. The driving force for this diffusion phenomenon is attributed to the oxygen potential gradient across the metal-oxide-gas system and the high oxygen affinity of these elements.
Chromium Diffusion in Sapphire Crystals: Influence of Preannealing Conditions
Authors: Gontier-Moya E. G. , Moya F. , Bigarre J. , Juve D. , Treheux D. , Grattepain C. 
Published: April 2011

ABSTRACTChromium diffusion coefficients in alumina single crystals were evaluated from penetration profiles determined by the SIMS technique. The samples were previously annealed at 1000°C (1 hour), 1500°C (4 hours), and 1700°C (24 hours). Diffusion experiments were carried out at 1400°C during 10 hours.The results show that bulk diffusion coefficients are strongly dependent on preannealing conditions (temperature and time): they decrease by more than an order of magnitude when the preannealing temperature is increased from 1000°C to 1700°C.These results are discussed taking into account the dislocations and point defects in alumina. We consider the role played by the linear defects resulting from surface polishing, as well as point defects associated with impurities. It is found that the lowest defect concentration is achieved after an annealing treatment at 1700°C during 24 hours. The conditions for obtaining a, «reference material» are proposed.
Proliferation of Human Osteoblastic Cells and Synthesis of Extracellular Bone Matrix on Biomaterials
Authors: Schaefer D. J. , Munder B. , Voigt M. , Stark G. B. 
Published: April 2011

AbstractPrimary human osteoblasts were cultered on biomaterials to develop living bone substitutes by Tissue Engineering. Monolayer cultures were established from iliac crest biopsies. Single cell suspensions were then seeded onto tricalciumphosphate (TCP) BIOBASE®, hydroxyapatitecollagen(HAC), autoclaved cancellous bone (CB) and fibrin glue (FG) Tissucol® The constructs were analyzed by electronmicroscopy, Cell proliferation assay (XTT) and histology to assess adhesion, proliferation and extracellular matrix formation on the biomaterial.The osteoblastic cells survived in the fibrin glue and established a mesenchymal phenotype. They adhered to the HAC-sponges, TCP and CB. Prolifertion was seen on TCP and CB. HAC had a suppressive effect on the cells. An inmature matrix was found on TCP and a bone neomatrix on CB after 4 weeks in vitro.
PEG Cross-Linked Alginate Hydrogels with Controlled Mechanical Properties
Authors: Eiselt Petra , Rowley Jon A. , Mooney David J. 
Published: April 2011

AbstractReconstruction of tissues and organs utilizing cell transplantation offers an attractive approach for the treatment of patients suffering from organ failure or loss. Highly porous synthetic materials are often used to mimic the function of the extracellular matrix (ECM) in tissue engineering, and serve as a cell delivery vehicle for the formation of tissues in vivo. Alginate, a linear copolysaccharide composed of D-mannuronic acid (M) and L-guluronic acid (G) units is widely used as a cell transplantation matrix. Alginate is considered to be biocompatible, and hydrogels are formed in the presence of divalent cations such as Ca2+, Ba2+and Sr2+. However, ionically cross-linked alginate gels continuously lose their mechanical properties over time with uncontrollable degradation behavior. We have modified alginate via covalent coupling of cross-linking molecules to expand and stabilize the mechanical property ranges of these gels. Several diamino PEG molecules of varying molecular weight (200, 400, 1000, 3400) were synthesized utilizing carbodiimide chemistry. Sodium alginate was covalently cross-linked with these cross-linking molecules, and mechanical properties of the resulting hydrogels were determined. The elastic modulus of the cross-linked alginates depended on the molecular weight of the cross-linking molecules, and ranged from 10-110 kPa. The theoretical cross-link density in the hydrogels was also varied from 3 to 47% (relative to the carboxylic groups in the alginate) and the mechanical properties were measured. The elastic modulus increased gradually and reached a maximum at a cross-link density of 15%. In summary, covalently coupled hydrogels can be synthesized which exhibit a wide range of mechanical properties, and these materials may be useful in a number of tissue engineering applications.
Biomolecular Surface Engineering of Materials for Controlling Bone Cell Adhesion and Spreading
Authors: Rezania A. , Healy K. E. 
Published: April 2011

AbstractModel biomaterial surfaces were modified with a peptide that contained a -RGD- (Arg-GlyAsp) sequence, unique to bone sialoprotein, to determine its effect on strength of adhesion, spreading, and focal contact formation of primary bone-derived cells. Peptide surfaces were fabricated by using a heterobifunctional crosslinker to graft the peptide to surfaces (quartz and silicon). Contact angle measurements, spectroscopic ellipsometry, and X-ray photoelectron spectroscopy were used to confirm the chemistry and thickness of the overlayers. Furthermore, spectroscopic ellipsometry was used to estimate the density of immobilized peptide on metal oxide surfaces. A radial flow apparatus was used to measure the strength of adhesion on peptide grafted surfaces. Following 20 min of cell incubation, the strength of cell adhesion was significantly (p<0.05) higher on the -RGD- compared to -RGE- (control) surfaces. The mean area of cells contacting the -RGD- surface was significantly (p<0.05) higher than -RGE- surfaces. Vinculin staining revealed formation of focal contact patches on the periphery of bone cells incubated for 4 hr on the -RGD- surfaces; however, cells seeded on the -RGE- grafted surfaces formed little or no focal contacts. The methods of peptide immobilization utilized in this study can be applied to medical devices, biosensors, and diagnostic assays that require specificity in cell adhesion.
Effect of the End of Range Loop Layer Depth on the Evolution of {311} Defects.
Authors: Raman R. , Law M. E. , Krishnamoorthy V. , Jones K. S. 
Published: April 2011

ABSTRACTThe interactions between end of range dislocation loops and {311} defects as a function of their proximity was studied. The dislocation loops were introduced at 2600 Å by a dual 1 × 1015 cm−2, 30 keV and a 1 × 1015 cm−2 , 120 keV Si+ implantation into Silicon followed by a anneal at 850 °C for 30 minutes. The depth of the loop layer from the surface was varied from 2600 Å to 1800 Å and 1000 Å by polishing off the Si surface using a chemical-mechanical polishing (CMP) technique. A post-CMP 1 × 1014 cm−2, 40 keV Si+ implantation was used to create point defects at the projected range of 580 Å. The wafers were annealed at 700, 800 and 900 °C and plan-view transmission electron microscopy (TEM) study was performed. It was found that the number of interstitials in {311} defects decreased as the projected range damage was brought closer to the loop layer, while the number of rectangular elongated defects (REDs) increased. Experimental investigation showed that REDs are formed at the end-of-range. It is concluded that the interstitials introduced at the projected range are trapped at the end-of-range dislocations. The REDs are formed due to the interactions between the interstitials and the pre-existing loops.
Stacked Layers of C-Induced Ge Quantum Dots
Authors: Schmidt O. G. , Eberl K. , Schieker S. , Jin-Phillipp N. Y. , Phillipp F. , Auerswald J. , Lamperter P. 
Published: April 2011

AbstractFifty layers of carbon-induced germanium dots, separated by 9.6 nm Si, are stacked by solid source molecular beam epitaxy. Each dot layer consists of 0.2 monolayers of pre-deposited carbon and 2.4 monolayers of post-grown Ge. These carbon-induced germanium dots are only 10 to 15 nm in diameter and 1 to 2 nm in height. Vertical alignment due to penetrating strain fields of underlying dot layers is not observed. Unlike to an identical structure without the pre-growth of carbon, a variety of advantageous aspects such as strain compensation, strongly enhanced no-phonon photoluminescence at a wavelength of around 1.3 μm and the possibility of effective waveguiding make this stack of C-induced Ge islands an attractive structure for Si based optoelectronic devices.
Magnetron Sputter Heteroepitaxy of Si1-x.Gex/Si(001): The Evolution of the Cross-Hatched Surface
Authors: Vögeli B. , Kummer M. , Känel H. Von 
Published: April 2011

AbstractThe surface step structure of step graded Si1-xGex buffers was investigated by scanning tunneling microscopy (STM). On pseudomorphically grown samples, single atomic steps were found, with the 2×8 reconstruction indicating Ge segregation. Upon strain relaxation, surface slips and the development of the cross-hatched surface takes place. Here, close to the surface slips, the step structure was found to consist of double height DA steps. This feature is not simply kinematically driven step bunching but can be attributed to the anisotropic strain field on the surface and to the Ge segregation. Analysis of STM cross-sections were taken to estimate the relaxation of our samples. The obtained values agree well with x-ray measurements. The relaxation is found to depend exponentially on the temperature, as theoretically expected.
Feasibility Of Novel Si-Based Interminiband Lasers
Authors: Sun Gregory , Friedman Lionel , Soref Richard A. 
Published: April 2011

AbstractWe have designed a parallel interminiband lasing in superlattice structures of coherently strained Si0.5Ge0.5/Si quantum wells (QWs). Population inversion is achieved between the non-parabolic heavy-hole valence minibands locally in-k-space. Lasing transition is at 5.4μm. Our analysis indicates that an optical gain of 134/cm can be obtained when the laser structure is pumped with a current density of 5kA/cm2.
Direct Optical Measurement of the valence band offset of p+ Si1−x−yGexCy/p− Si (100) by Heterojunction Internal Photoemission
Authors: Chang C. L. , Rokhinson L. P. , Sturm J. C. 
Published: April 2011

AbstractOptical absorption measurements have been performed to study the effect of carbon on the valence band offset of compressively strained p+ Si1−x−yGexCy/(100) p− Si heterojunction internal photoemission structures grown by Rapid Thermal Chemical Vapor Deposition (RTCVD) with substitutional carbon levels up to 2.5%. Results indicated that carbon decreased the valence band offset by 26 ± 1 meV/ %C. Results from optical measurement in this study agreed with previous data from capacitance-voltage measurements. Based on previous reports of carbon effect on the bandgap of compressively strained Si1−x−yGexCy, our work suggests that the effect of carbon incorporation on the band alignment of Si1−x−yGexCy/Si is to reduce the valence band offset, with a negligible effect on the conduction band alignment.
SiGe RF - Electronic: Devices, Circuits, Competitors, Markets
Authors: König U. 
Published: April 2011

AbstractThe outstanding performance of the SiGe/Si heterosystem and its compatibility to the dominating Si-technology, opens perspectives for a new generation of high volume microelectronic components, just for communication markets. This paper reviews device and circuit results from experiments and simulations for SiGe HBTs and for SiGe HFETs, and compares those to device results made from competitive materials. Figures of merit considered are gains, transconductances, frequencies, noise, power, delays and bandwidths.