15,691 research outputs found
Amorphous metallic films in silicon metallization systems
The general objective was to determine the potential of amorphous metallic thin films as a means of improving the stability of metallic contacts to a silicon substrate. The specific objective pursued was to determine the role of nitrogen in the formation and the resulting properties of amorphous thin-film diffusion barriers. Amorphous metallic films are attractive as diffusion barriers because of the low atomic diffusivity in these materials. Previous investigations revealed that in meeting this condition alone, good diffusion barriers are not necessarily obtained, because amorphous films can react with an adjacent medium (e.g., Si, Al) before they recrystallize. In the case of a silicon single-crystalline substrate, correlation exists between the temperature at which an amorphous metallic binary thin film reacts and the temperatures at which the films made of the same two metallic elements react individually. Amorphous binary films made of Zr and W were investigated. Both react with Si individually only at elevated temperatures. It was confirmed that such films react with Si only above 700 C when annealed in vacuum for 30 min. Amorphous W-N films were also investigated. They are more stable as barriers between Al and Si than polycrystalline W. Nitrogen effectively prevents the W-Al reaction that sets in at 500 C with polycrystalline W
Symmetry and Z_2-Orbifolding Approach in Five-dimensional Lattice Gauge Theory
In a lattice gauge-Higgs unification scenario using a Z_2-orbifolded
extra-dimension, we find a new global symmetry in a case of SU(2) bulk gauge
symmetry. It is a global symmetry on sites in a fixed point with respect to
Z_2-orbifolding, independent of the bulk gauge symmetry. It is shown that the
vacuum expectation value of a Z_2-projected Polyakov loop is a good order
parameter of the new symmetry. The effective theory on lattice is also
discussed.Comment: 13 pages, 3 figures; refined the explanation
Vacuum Structure of the Ichimatsu-Decomposed Lattice Models
We proposed an `Ichimatsu'-decomposed lattice gauge theory with fermionic
symmetries. The vacuum structures of the gauge sector with two coupling
constants () are investigated for 3-dimensional Z and
4-dimensional SU(2) cases using mean-field approximation and numerical
simulation. We found two phases on the () phase diagram for
3-dim. Z case, while the diagram is a single phase for the latter.Comment: 3 pages, 6 figures, Lattice2002(higgssusy
An Approach to Higher Dimensional Theories Based on Lattice Gauge Theory
A higher dimensional lattice space can be decomposed into a number of
four-dimensional lattices called as layers. The higher dimensional gauge theory
on the lattice can be interpreted as four-dimensional gauge theories on the
multi-layer with interactions between neighboring layers. We propose the new
possibility to realize the continuum limit of a five-dimensional theory based
on the property of the phase diagram.Comment: Lattice2003(higgs
Staggered Fermion, its Symmetry and Ichimatsu-Patterned Lattice
We investigate exact symmetries of a staggered fermion in D dimensions. The
Dirac operator is reformulated by SO(2D) Clifford algebra. The chiral symmetry,
rotational invariance and parity symmetries are clarified in any dimension.
Local scalar and pseudo-scalar modes are definitely determined, in which we
find non-standard modes. The relation to Ichimatsu-patterned lattice approach
is discussed.Comment: 3 pages, 1 figure, "Talk at Lattice2004(theory), Fermilab, June
21-26, 2004
Supersonic flow calculation using a Reynolds-stress and an eddy thermal diffusivity turbulence model
A second-order model for the velocity field and a two-equation model for the temperature field are used to calculate supersonic boundary layers assuming negligible real gas effects. The modeled equations are formulated on the basis of an incompressible assumption and then extended to supersonic flows by invoking Morkovin's hypothesis, which proposes that compressibility effects are completely accounted for by mean density variations alone. In order to calculate the near-wall flow accurately, correction functions are proposed to render the modeled equations asymptotically consistent with the behavior of the exact equations near a wall and, at the same time, display the proper dependence on the molecular Prandtl number. Thus formulated, the near-wall second order turbulence model for heat transfer is applicable to supersonic flows with different Prandtl numbers. The model is validated against flows with different Prandtl numbers and supersonic flows with free-stream Mach numbers as high as 10 and wall temperature ratios as low as 0.3. Among the flow cases considered, the momentum thickness Reynolds number varies from approximately 4,000 to approximately 21,000. Good correlation with measurements of mean velocity, temperature, and its variance is obtained. Discernible improvements in the law-of-the-wall are observed, especially in the range where the big-law applies
Gravitational energy in a small region for the modified Einstein and Landau-Lifshitz pseudotensors
The purpose of the classical Einstein and Landau-Lifshitz pseudotensors is
for determining the gravitational energy. Neither of them can guarantee a
positive energy in holonomic frames. In the small sphere approximation, it has
been required that the quasilocal expression for the gravitational
energy-momentum density should be proportional to the Bel-Robinson tensor
. However, we propose a new tensor
which is the sum of certain tensors
and , it has certain properties
so that it gives the same gravitational "energy-momentum" content as
does. Moreover, we show that a modified Einstein
pseudotensor turns out to be one of the Chen-Nester quasilocal expressions,
while the modified Landau-Lifshitz pseudotensor becomes the Papapetrou
pseudotensor; these two modified pseudotensors have positive gravitational
energy in a small region.Comment:
- …