1,106 research outputs found
Low stress polysilicon film and method for producing same
Multi-layer assemblies of polysilicon thin films having predetermined stress characteristics and techniques for forming such assemblies are disclosed. In particular, a multi-layer assembly of polysilicon thin film may be produced that has a stress level of zero, or substantially so. The multi-layer assemblies comprise at least one constituent thin film having a tensile stress and at least one constituent thin film having a compressive stress. The thin films forming the multi-layer assemblies may be disposed immediately adjacent to one another without the use of intermediate layers between the thin films
Contact Atomic Structure and Electron Transport Through Molecules
Using benzene sandwiched between two Au leads as a model system, we
investigate from first principles the change in molecular conductance caused by
different atomic structures around the metal-molecule contact. Our motivation
is the variable situations that may arise in break junction experiments; our
approach is a combined density functional theory and Green function technique.
We focus on effects caused by (1) the presence of an additional Au atom at the
contact and (2) possible changes in the molecule-lead separation. The effects
of contact atomic relaxation and two different lead orientations are fully
considered. We find that the presence of an additional Au atom at each of the
two contacts will increase the equilibrium conductance by up to two orders of
magnitude regardless of either the lead orientation or different group-VI
anchoring atoms. This is due to a LUMO-like resonance peak near the Fermi
energy. In the non-equilibrium properties, the resonance peak manifests itself
in a large negative differential conductance. We find that the dependence of
the equilibrium conductance on the molecule-lead separation can be quite
subtle: either very weak or very strong depending on the separation regime.Comment: 8 pages, 6 figure
Electron Transport Through Molecules: Self-consistent and Non-self-consistent Approaches
A self-consistent method for calculating electron transport through a
molecular device is proposed. It is based on density functional theory
electronic structure calculations under periodic boundary conditions and
implemented in the framework of the nonequilibrium Green function approach. To
avoid the substantial computational cost in finding the I-V characteristic of
large systems, we also develop an approximate but much more efficient
non-self-consistent method. Here the change in effective potential in the
device region caused by a bias is approximated by the main features of the
voltage drop. As applications, the I-V curves of a carbon chain and an aluminum
chain sandwiched between two aluminum electrodes are calculated -- two systems
in which the voltage drops very differently. By comparing to the
self-consistent results, we show that this non-self-consistent approach works
well and can give quantitatively good results.Comment: 11 pages, 10 figure
Electron Transport Through Molecules: Gate Induced Polarization and Potential Shift
We analyze the effect of a gate on the conductance of molecules by separately
evaluating the gate-induced polarization and the potential shift of the
molecule relative to the leads. The calculations use ab initio density
functional theory combined with a Green function method for electron transport.
For a general view, we study several systems: (1) atomic chains of C or Al
sandwiched between Al electrodes, (2) a benzene molecule between Au leads, and
(3) (9,0) and (5,5) carbon nanotubes. We find that the polarization effect is
small because of screening, while the effect of the potential shift is
significant, providing a mechanism for single-molecule transistors.Comment: 4 pages, 4 figure
Large area polysilicon films with predetermined stress characteristics and method for producing same
Multi-layer assemblies of polysilicon thin films having predetermined stress characteristics and techniques for forming such assemblies are disclosed. In particular, a multi-layer assembly of polysilicon thin films may be produced that has a stress level of zero, or substantially so. The multi-layer assemblies comprise at least one constituent thin film having a tensile stress and at least one constituent thin film having a compressive stress. The thin films forming the multi-layer assemblies may be disposed immediately adjacent to one another without the use of intermediate layers between the thin films. Multi-layer assemblies exhibiting selectively determinable overall bending moments are also disclosed. Selective production of overall bending moments in microstructures enables manufacture of such structures with a wide array of geometrical configurations
Covariant Field Equations, Gauge Fields and Conservation Laws from Yang-Mills Matrix Models
The effective geometry and the gravitational coupling of nonabelian gauge and
scalar fields on generic NC branes in Yang-Mills matrix models is determined.
Covariant field equations are derived from the basic matrix equations of
motions, known as Yang-Mills algebra. Remarkably, the equations of motion for
the Poisson structure and for the nonabelian gauge fields follow from a matrix
Noether theorem, and are therefore protected from quantum corrections. This
provides a transparent derivation and generalization of the effective action
governing the SU(n) gauge fields obtained in [1], including the would-be
topological term. In particular, the IKKT matrix model is capable of describing
4-dimensional NC space-times with a general effective metric. Metric
deformations of flat Moyal-Weyl space are briefly discussed.Comment: 31 pages. V2: minor corrections, references adde
Fermions and noncommutative emergent gravity II: Curved branes in extra dimensions
We study fermions coupled to Yang-Mills matrix models from the point of view
of emergent gravity. The matrix model Dirac operator provides an appropriate
coupling for fermions to the effective gravitational metric for general branes
with nontrivial embedding, albeit with a non-standard spin connection. This
generalizes previous results for 4-dimensional matrix models. Integrating out
the fermions in a nontrivial geometrical background induces indeed the
Einstein-Hilbert action of the effective metric, as well as additional terms
which couple the Poisson tensor to the Riemann tensor, and a dilaton-like term.Comment: 34 pages; minor change
Methods to model and predict the ViewRay treatment deliveries to aid patient scheduling and treatment planning
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