bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stacking-Fault Energies in Silicon, Diamond, and Silicon Carbide
Authors: Denteneer P. J. H. 
Published: March 2011

AbstractStacking faults in a perfect crystal can be seen as limiting structures of certain series of polytypes of that crystal. A parametrization of the energy of polytypes in terms of interaction constants between layers therefore allows for the calculation of stacking-fault energies. The first-principles pseudopotential-density-functional method is used to calculate total energies of a few simple polytypes of silicon and carbon. The energies of intrinsic and extrinsic stacking faults (γISF and γESF , respectively) in silicon and diamond that follow from these calculations are in much better agreement with available experimental numbers than in previous theoretical approaches. I find: γISF = 47 mJm-2 and γESF = 36 mJm-2 for Si, γISF = 300 mJm-2 and γESF = 253 mJm-2 for diamond. From recently published similar calculations for polytypes of silicon carbide one obtains a negative energy for the extrinsic stacking fault, if zincblende silicon carbide is taken as the unfaulted structure, suggesting the observed occurrence in nature of polytypism in silicon carbide.
Molecular Dynamics Studies of Silicon Solidification and Melting
Authors: Grabow Marcia H. , Gilmer George H. , Bakker Aloysius F. 
Published: March 2011

AbstractThe motion of the crystal-melt interface of silicon has been investigated using molecular dynamics computer simulations. Solidification and melting have been studied for the diamond cubic (111) and (100) interfaces using the Stillinger-Weber interatomic potential for silicon. These results are compared with theory, and also with experimental results.
Atomistic Simulations of Interfaces in Metals and Alloys
Authors: Chen S. P. 
Published: March 2011

AbstractWe have used embedded atom potentials to simulate the surfaces, thin films and grain boundaries in metals (Ni and Al) and alloys (NiAl and Ni3Al). The calculated surface relaxations and ripplings of free surfaces are in good agreement with experiments. A new interference phenomena of interlayer relaxation in thin films are observed in the simulation. The segregation behavior of B and S and their effects on the mechanical properties of Ni3Al are correctly predicted with potentials fitted to data obtained by electronic band structure calculations.
Full Potential, Total Energy Lmto Calculation of Interface Structure in Ti-C and W-C Superlattices
Authors: Price David L. , Cooper Bernard R. 
Published: March 2011

AbstractWe discuss calculations of the electronic and crystallographic structure at the interfaces of titanium-carbon and tungsten-carbon superlattices. Specifically, we present total energy calculations for an arrangement of atoms designed to allow direct investigation of the competition between the formation of M-C bonds and C-C bonds. We conclude that the equilibrium structure is dominated by C-C bonding and so find that the interface has a graphite-like atomic arrangement rather than a carbide-like arrangement. These total energy calculations have been performed using a recently developed self-consistent linear combination of muffin-tin orbitals electronic structure method. This is a full-potential, all-electron, variation on standard LMTO electronic structure methods and, along with careful self-consistent determination of the parameters involved, allows accurate total energy calculations of the type of low symmetry systems involved in this study.
Computer Simulations of Epitaxial Interfaces
Authors: Dregia S. A. , Wynblatt P. , Bauer C. L. 
Published: March 2011

AbstractThe embedded-atom method was applied in computer simulations to study epitaxial Cu/Ag interfaces in cube-on-cube orientation relationship. Coherent and semicoherent interfaces were studied with inclinations parallel to (001), (011) and (111). The coherent boundary energy depends strongly on the predicted enthalpy of mixing. The interfacial energy for semicoherent boundaries was highly anisotropic, having its largest value (549 mJ/m2) for the (011) interface and its smallest value (231 mJ/m2) for the (111) interface. The periodic elastic relaxations correspond to networks of misfit dislocations lying in the plane of the interface; the maximum displacement in the (011) interface is about one-third the atomic diameter, but only one-eighth the atomic diameter in the (111) interface.
Mechanisms of Molecular Beam Epitaxial Growth on Reconstructed Si{100}: Thermal and Energized Beams
Authors: Garrison B. J. , Miller M. T. , Brenner D.W. 
Published: March 2011

Summary:Molecular dynamics simulations have been performed that examine the microscopic mechanisms of rearrangements of atoms on the Si{ 1001 surface due to deposition of gas phase atoms. For thermal energy deposition we find that the gas atoms initially attach to dangling bonds of the surface dimer atoms. The dimer ’unreconstruction’ is due to a diffusion event on the surface, thus is temperature activated. We also find that dimers may open in regions of the surface where there are several atoms not at lattice sites, thus a low temperature amorphous structure. For 5-10 eV deposition there are direct mechanisms of dimer opening that occur on the 50-100 fs timescale. For energies greater than 15-20 eV there is implantation of the silicon atoms which leads to subsurface damage.
Beyond the Embedded Atom Interatomic Potential
Authors: Savino Eduardo J. , Pasianot R. 
Published: March 2011

AbstractWe briefly discuss some of the advantages and limitations of using embedded atom interatomic potentials for simulating the static configuration and dynamics of lattice defects. In metals, the embedded atom potentials provide a physically more realistic approximation than simple pair interaction potentials without a significant increase in computer time needed for defect simulation studies. However, in some cases, n-body shear forces, i.e bond angle interatomic forces may be needed for fitting experimental results related to defect configuration. One such example is the elastic neutron scattering data from N interstitials in Nb [1]. Also, such bond angle forces must be included in a realistic model of atomic interactions in metals, expecially in highly anisotropic bee transition metals. Extending the concept of the embedded atom method, we propose a new form for the interatomic potential in metals which includes bond angle forces. General expressions for the elastic constants in bee and fee structures are deduced.
A Semi-Empirical Potential for Graphite
Authors: Oh D. J. , Johnson R. A. 
Published: March 2011

AbstractAn Embedded Atom Method Model for graphite has been derived based on a short-range Morse two-body potential and an electron density function with both radial and angular terms. This part of the model involves interaction only within a hexagonal plane, and the interaction between planes is approximated by a Buckingham potential. The model is stable with respect to fcc, bcc, and diamond structures. The effective two-body potential is very small, indicating that defect properties are dominated by the noncentral many-body interactions.
A First-Principles Calculation of the Resistivity and Thermopower in Strong-Scattering Alloys
Authors: Brown Randall H. , Allen Philip B. , Nicholson Donald M. , Butler William H. 
Published: March 2011

AbstractWe investigate the concentration and short-range order dependence of the zero-temperature resistivity and thermopower for substitutionally disordered alloys from a first-principles approach. The alloy disorder is simulated by calculating the electronic structure of a large supercell (typically 200–250 atoms) with periodic boundary conditions. For the strong-scattering alloys we consider, the electron mean-free path is much less than the supercell dimension, causing artificial effects of periodicity to be negligible. In spite of strong scattering, there is no evidence for localized states near EF. The resistivity and thermopower are averaged over several configurations resulting in statistical error bounds of approximately ±10%. The concentration-dependent resistivity of substitutional V1−xAlx alloys agree well with Korringa-Kohn-Rostoker coherent potential approximation (KKR CPA) calculations. This confirms the accuracy of KKR CPA theory.
Bubble Dynamics in Polymer Melts
Authors: Briscoe Brian J. , Chaudhary Bharat I. 
Published: March 2011

AbstractA system has been developed for studying the dynamic behaviour of gas bubbles in liquid media and is currently being used to investigate the behaviour of a single nitrogen bubble in molten LDPE. It involves the formation of an initial gas-liquid interface from a capillary by direct injection of the gas into the melt, subsequent growth until an equilibrium state is reached and the application of ambient pressure ramps which result in bubble expansion or contraction. The response depends on the rate of change of the ambient pressure. Experiments have been conducted at various temperatures above the crystalline melting temperature, Tm, of LDPE in the range 120°C-150°C. The numerical data acquired are in the form of pressure and temperature values, and these data are superimposed on stored video images of the bubbles for further processing on an image analyser whereby bubble sizes and shapes are determined.The results obtained reveal the effect of melt viscoelasticity on the dynamics of bubbles in highly viscous fluid media. Furthermore, the changes in bubble shapes with time due to buoyancy effects are also shown. Clearly, the bubble response in the melt is governed by a combination of viscous and elastic effects. However, in the absence of suitable viscous solutions to the problem, we have attributed the behaviour to a time-dependent elastic response, but only as a first order approximation.
Corrosion of Aluminum Interconnect Passivated with Polyimide or Silicon Nitride
Authors: Comizzoli R. B. , Opila R. L. , Wong Y. H. 
Published: March 2011

Polyimides have been considered the most promising organic polymers for use as an inner-layer dielectric or over-metal passivation layer on ICs. These polymers have certain processing advantages over traditional inorganic dielectrics such as SiO2 or Si3N4. However, polyimide (PI) must meet the stringent standards that inorganic materials have met, including good adhesion to the substrate and resistance to diffusion of water. Failure to meet these standards may result in increased aluminum corrosion rate and consequent degraded reliability.In this study, the corrosion rate of sputtered aluminum test patterns passivated with either PI or plasma-deposited silicon nitride (SiN) was measured at 85°C and 85% relative humidity (RH). The objectives of this work were to: (1) assess the failure rates of biased aluminum interconnection with PI or SiN passivation; (2) determine the failure mechanisms in each case; and (3), as a result, evaluate the suitability of PI passivation for high voltage ICs in non-hermetic packages. In this report, the test device fabrication and evaluation procedures are first described. Then the results are presented, including both the failure rate measurements and the failure analyses. Finally, the results are compared and discussed.
Ion Beam Modification of Silicone Rubber
Authors: Suzuki Yoshiaki , Kusakabe Masahiro , Iwaki Masaya , Suzuki Masaaki 
Published: March 2011

AbstractIon implantation in silicone rubber has been carried out in order to study its effects on structure and chemical states. H+-, He+-, C+-, N+-, N2+-, O+-, O2+-, Ne+-, Na+-, Ar+-, and K+- ion implantations were performed at an energy of 150 keV with doses ranging from 1×1013 to 1×1017 ions/cm2 at room temperature. The depth profiles of the ion implanted elements and host elements were investigated by means of XPS and SIMS. The chemical properties were studied by FT-IR-ATR and Raman spectroscopy. XPS results indicated that most of the implanted elements showed a Gaussian like distribution in the silicone polymer matrix, but implanted He+, Ne+, and Ar+ could not be detected. Results of FT-IR-ATR showed that ion implantation broke CH3 and Si-O bonds to form new radicals such as SiOH, >C=0, CH2 and SiHx and the effects varied depending on the implanted ion species. The Raman spectroscopy results showed that ion implanted silicone contained both sp3 and sp2 bonded carbon.
“Automatized” Peel Testing: Calculated Stresses and Deflections in the Film
Authors: Suhir Ephraim 
Published: March 2011

AbstractFilm adhesion, which is an important reliability factor in many microelectronic structures, is usually evaluated by peel testing. The loading and the peel angle in peel tests can be controlled best if these tests are “automatized”, which could be done, for instance, by applying air pressure to a film through an opening in the substrate. We consider a rectangular opening and determine, how this pressure is related to the peel (membrane) loading and peel angle for the given film material and thickness. Our study is based on von-Kármán's equations for large deflections of plates. The obtained results provide mechanical fundamentals for a rational physical design of a peel test vehicle.
Xps Study of the Interface of Polyimide on Cr and Ni.
Authors: Garilli Marco , Marletta Giovanni , Puglisi Orazio , Oliveri Carmelo , Magro Carmelo , Ferla Giuseppe 
Published: March 2011

AbstractThe paper presents a study of three polyimide-oxide interfaces. The Cr-oxide-PI interface seems to undergo a drastic topographical structural rearrangement. The case of the Ni surface is indicative of heavy decomposition of the Ni oxide which induces the decomposition of the polymer film. On the contrary the stabilized Ni surface behaves in a normal manner indicating that the driving force for the decomposition is the instability of the oxide.
Ftir and Xps Studies of Polyimide/Metal Interface Formation
Authors: Stewart William C. , Leu Jihperng , Jensen Klavs F. 
Published: March 2011

AbstractWe describe infrared and x-ray photoelectron spectroscopy studies of the interfaces formed when the PMDA/ODA polyamic acid is imidized on gold, chromium, and copper. Polyimide films ranging from 34 ° to 1328 ° are analyzed as part of these studies. The IR and XPS results indicate that the gold interacts very little with the polyimide, while copper produces significant changes in the IR and XPS spectra. At elevated cure temperatures passivated chromium also reacts with the polyimide. In structures with chromium and copper, the thermal stability of the polyimide at the interface is reduced from that of bulk polyimide. The data demonstrate that the metals interact with the polymer structure at the point where ring closure occurs to form the polyimide from polyamic acid.
Elastic Softening in Nanocrystalline Silicon
Authors: Phillpot S. R. , Wolf D. , Lutsko J. F. 
Published: March 2011

AbstractIt is pointed out that some of the generic physical properties of a nanocrystalline material are similar to those of a grain-boundary superlattice. The structure and elastic properties of a superlattice of twist boundaries on the (110) plane of silicon are calculated as a function of modulation wavelength using a three-body potential. All elastic moduli are found to be softened. This softening is attributed to the relatively small amount of structural disorder at the interfaces.
Mechanical Properties of Metallic Interfaces
Authors: Walley K. P. , Gellman A. J. 
Published: March 2011

AbstractWe have constructed an instrument designed to make measurements of interfacial mechanical properties under ultra-high vacuum conditions. The device has been configured to allow two metallic surfaces to be prepared and characterized independently within a single UHV chamber. The two can then be brought into contact to allow measurements of the frictional properties of their interface. In this manner we are able to study the frictional properties of metallic surfaces modified by the presence of mono-molecular films. The instrument is described in this paper as are the results of initial measurements performed on modified tungsten surfaces. In addition we address the question of why it is that such ultra-thin films can modify the mechanical properties of surfaces brought into contact under macroscopic loads.
Scanning Auger and Xps Studies of Fracture Surfaces of B4C Hot Pressed with Excess Carbon
Authors: DeKoven Benjamin M. , Ness Eric A. , Hawn David D. 
Published: March 2011

AbstractA series of boron carbide materials was hot pressed with 0-7% excess carbon. The strength of each material was determined by four point bending, and found to decrease from about 600MPa to 300MPa as the carbon content increased from 0% to 7%. Diamond indentation yielded hardness values that decreased from 28.3 to 25.OGPa and toughness values that increased from 3.5 to 4.5 MPa√mover the same carbon range. Each sample was fractured in situ in ultrahigh vacuum (UHV) and examined by scanning Auger microanalysis (SAM) and XPS to determine both the elemental and chemical state distributions. For the samples with excess carbon, localized carbonrich regions are observed on fracture surfaces by SAM. XPS reveals a 50% enhancement of excess carbon on the fracture surface compared to the bulk for the sample with 7% excess carbon. A correlation was observed between surface carbon composition and the bulk toughness and hardness. The C(ls) XPS spectra were utilized to determine the nature of carbon in B4C on freshly fractured and Ne+bombarded surfaces. Two distinct peaks were observed in the C(ls) region. Low dose ion bombardment resulted in a single broad C(ls) peak at the midpoint of the two initial peaks. It can be inferred from this data that there are C-C-C intericosahedral linkages in B4C.
The Effect of Residual Stresses on the Rupture Properties of Film/Substrate Samples
Authors: Ignat M. , Chouaf A. , Bernard C. , Terriez J.M. 
Published: March 2011

AbstractThe residual stresses of two different film/substrate systems were calculated. Besides, several micromechanical tests were performed. Joining the calculated residual stresses to the analysis of the experimental results, some insight on the interfacial adhesion of film/substrate systems is presented.
Residual Stress Analysis of A Multi-Layer Thin Film Structure by Destructive (Curvature) and Non-Destructive (X-Ray) Methods
Authors: Chen P.C. , Oshida Yoshiki 
Published: March 2011

AbstractMulti-layer thin film which has structure of Cu/Cr/K/Cr/Cu prepared by sputtering process was analyzed for interfacial stresses for as-deposited conditions. This structure was also annealed at 150°C, 250°C, and 350°C for around 15 min. in a vacuum and cooled slowly down for stress analyses.Equations derived by Osgood [1] for residual stress estimations for homogeneous material system using layer removal technique (stress relief) is now applied for inhomogeneous system (multilayer structure). The results are compared with the data obtained from x-ray diffraction technique by using sin2Ψ-2θ method, for Cu layer.From the present analyses, the data obatined using layer removal seem to be qualitatively consistent with but not quantitatively in agreement with x-ray method. Data obtained using the layer removal method have some overlaps with those obtained from x-ray technique. However, in details, data from the curvature method present different scattering band from the x-ray method. It is suggested that the layer removal method is more practical to be used to estimate the average residual stress of the multi-layer system not only because the layer removal method estimates the bulk behavior but also when the metal film is thin (e.g., 200A for Cr layer), x-ray technique becomes impractical. By annealing the sputtered structure up to 250°C, the residual stresses, in particularly Cu layer, decreased on both sides in x- and y-directions.From the main results drawn from the present studies, the layer removal sequence for the curvature method shows significant affects on the obtained results of residual stresses. Minimizing influences caused by layer removal sequences as well as removing duration and temperature provides the most accurate results on residual stress measurements.
Study of Contact Angles of Metals and Alloys on the Superconducting YBa2Cu3O7-x
Authors: Chan Siu-Wai , Bader W. G. , Yeung N. S. , Hull G. W. 
Published: March 2011

AbstractWettability and contactibility of selected metals and alloys on superconducting YBa2Cu3O7-x were studied. Droplets of metals and alloys were formed by melting short segments of wires on pellets of YBa2Cu3O7-x The wires were melted in a rapid thermal annealer with an oxygen atmosphere to lessen the oxygen loss from the YBa2Cu3O7-x surface. The contact angles of the solidified droplets on the pellets were measured from the micrographs taken with a scanning electron microscope. Contact angles less than 90° were obtained with Pb and Ag, while angles greater than 90° were obtained with Bi metal, 40Pb/60Sn, and 99Pb/lSb alloys. Pb alloyed with either Sn or Sb increased the wetting angles. The contact angles provided a direct measurement of wetting characteristics and were used to relate various surface energies and the work of adhesion between tested metallic systems and YBa2Cu3O7-x.
Mechanical Damping and Dynamic Modulus Measurements in Continuous Fiber-Reinforced Composite Materials: Al/Al2O3 and Al/W
Authors: Wolfenden Alan , Wolla Jeffrey M. 
Published: March 2011

AbstractMeasurements of mechanical damping, or internal friction (Q−1), and dynamic Young's modulus (E) have been made near 80 kHz and at strain amplitudes (ε) in the range of 10−8 to 10−4 on small specimens of the following two continuous fiber-reinforced metal matrix composites (MMCs): 6061 aluminum reinforced with alumina (Al/A12O3) and 6061 aluminum reinforced with tungsten (AI/W). Baseline experiments were also performed on 99.999% aluminum (pure Al) for comparison puposes. The temperature (T) dependence of modulus up to 475°C was determined for AI/A12O3 and pure Al. The rate of modulus decrease with increasing temperature for AI/A12O3 and Al was the same, that is, dE/dT was essentially the same for both materials. Thus, the reduction in modulus observed for the Al/Al2O3 was attributed to the reduction in modulus of the Al matrix and not that of the Al2O3 fibers. The strain amplitude dependence of damping was examined for all three materials. The pure Al exhibited classical dislocation damping behavior with strain amplitude dependent damping starting at a strain of 2 × 10−5. The Al/Al2O3 specimens showed only mild dependence of damping on strain amplitude starting at strains near 10−5. The AI/W exhibited significant amplitude dependence of damping starting at strains of 2 × 10−6 with the fiber diameter being a major factor in determining the damping behavior. The Q−1 versus ε data for Al/Al2O3, when analyzed in terms of the Granato-Lücke (GL) theory for dislocation damping, yielded minor pinning lengths of dislocations near 10−8 m and mobile dislocation densities near 1011 m−2. The same analysis for the Al/W data gave values near 10−8 m for the minor pinning lengths and 1012 M−2 for the dislocation density. Relative to the results for pure Al, the minor pinning lengths for Al/Al2O3 and AL/W are comparable (10−8 m for pure Al), but the dislocation densities are much higher (109 m−2 found in the pure Al). The relatively high dislocation densities calculated for these aluminum matrix MMCs agree with previous findings of other researchers and may be associated with the fiber/matrix interface.