2,201 research outputs found
Baryon states with hidden charm in the extended local hidden gauge approach
The s-wave interaction of and , is studied within a unitary coupled channels scheme
with the extended local hidden gauge approach. In addition to the
Weinberg-Tomozawa term, several additional diagrams via the pion-exchange are
also taken into account as box potentials. Furthermore, in order to implement
the full coupled channels calculation, some of the box potentials which mix the
vector-baryon and pseudoscalar-baryon sectors are extended to construct the
effective transition potentials. As a result, we have observed six possible
states in several angular momenta. Four of them correspond to two pairs of
admixture states, two of - with , and two of - with . Moreover, we find a resonance which couples to
the channel and one spin degenerated bound state of
with .Comment: 24 pages, 6 figure
Correlation Functions in Two-Dimensional Dilaton Gravity
The Liouville approach is applied to the quantum treatment of the dilaton
gravity in two dimensions. The physical states are obtained from the BRST
cohomology and correlation functions are computed up to three-point functions.
For the case (i.e., without matter), the cosmological term operator is
found to have the discrete momentum that plays a special role in the
Liouville gravity. The correlation functions for arbitrary numbers of operators
are found in the case, and are nonvanishing only for specific
``chirality'' configurations.Comment: 14 pages, TIT/HEP-204, STUPP-92-13
Metal-catalyst-free growth of carbon nanotubes and their application in field-effect transistors
The metal-catalyst-free growth of carbon nanotubes (CNTs) using chemical vapor deposition and the application in field-effect transistors (FETs) is demonstrated. The CNT growth process used a 3-nm-thick Ge layer on SiO2 that was subsequently annealed to produce Ge nanoparticles. Raman measurements show the presence of radial breathing mode peaks and the absence of the disorder induced D-band, indicating single walled CNTs with a low defect density. The synthesized CNTs are used to fabricate CNTFETs and the best device has a state-of-the-art on/off current ratio of 3×108 and a steep sub-threshold slope of 110 mV/dec
Baryon states with open charm in the extended local hidden gauge approach
In this paper we examine the interaction of and states,
together with their coupled channels, by using an extension of the local hidden
gauge formalism from the light meson sector, which is based on heavy quark spin
symmetry. The scheme is based on the use of the impulse approximation at the
quark level, with the heavy quarks acting as spectators, which occurs for the
dominant terms where there is the exchange of a light meson. The pion exchange
and the Weinberg-Tomozawa interactions are generalized and with this dynamics
we look for states generated from the interaction, with a unitary coupled
channels approach that mixes the pseudoscalar-baryon and vector-baryon states.
We find two states with nearly zero width which are associated to the
and . The lower state, with ,
couples to and , and the second one, with , to . In addition to these two states, we find four more states with
, one of them nearly degenerate in two states of .
Furthermore we find three states in , two of them degenerate in .Comment: v3: version to appear in Eur.Phys.J.
Description of as a system with the fixed center approximation
We study the system with an aim to describe the
resonance. The chiral unitary approach has achieved success in a description of
systems of the light hadron sector. With this method, the system in
the isospin sector , is found to be a dominant component of the resonance. Therefore, by regarding the system as a cluster,
the resonance, we evaluate the system applying the
fixed center approximation to the Faddeev equations. We construct the
unitarized amplitude using the chiral unitary approach. As a result, we find a
peak in the three-body amplitude around 1739 MeV and a width of about 227 MeV.
The effect of the width of and is also discussed. We
associate this peak to the which has a mass of MeV
and a width of MeV
Depletion isolation effect in Vertical MOSFETS during transition from partial to fully depleted operation
A simulation study is made of floating-body effects (FBEs) in vertical MOSFETs due to depletion isolation as the pillar thickness is reduced from 200 to 10 nm. For pillar thicknesses between 200–60 nm, the output characteristics with and without impact ionization are identical at a low drain bias and then diverge at a high drain bias. The critical drain bias Vdc for which the increased drain–current is observed is found to decrease with a reduction in pillar thickness. This is explained by the onset of FBEs at progressively lower values of the drain bias due to the merging of the drain depletion regions at the bottom of the pillar (depletion isolation). For pillar thicknesses between 60–10 nm, the output characteristics show the opposite behavior, namely, the critical drain bias increases with a reduction in pillar thickness. This is explained by a reduction in the severity of the FBEs due to the drain debiasing effect caused by the elevated body potential. Both depletion isolation and gate–gate coupling contribute to the drain–current for pillar thicknesses between 100–40 nm
Asymmetric gate induced drain leakage and body leakage in vertical MOSFETs with reduced parasitic capacitance
Vertical MOSFETs, unlike conventional planar MOSFETs, do not have identical structures at the source and drain, but have very different gate overlaps and geometric configurations. This paper investigates the effect of the asymmetric source and drain geometries of surround-gate vertical MOSFETs on the drain leakage currents in the OFF-state region of operation. Measurements of gate-induced drain leakage (GIDL) and body leakage are carried out as a function of temperature for transistors connected in the drain-on-top and drain-on-bottom configurations. Asymmetric leakage currents are seen when the source and drain terminals are interchanged, with the GIDL being higher in the drain-on-bottom configuration and the body leakage being higher in the drain-on-top configuration. Band-to-band tunneling is identified as the dominant leakage mechanism for both the GIDL and body leakage from electrical measurements at temperatures ranging from ?50 to 200?C. The asymmetric body leakage is explained by a difference in body doping concentration at the top and bottom drain–body junctions due to the use of a p-well ion implantation. The asymmetric GIDL is explained by the difference in gate oxide thickness on the vertical (110) pillar sidewalls and the horizontal (100) wafer surface
Depletion-Isolation Effect in Vertical MOSFETs During the Transition From Partial to Fully Depleted Operation
A simulation study is made of floating-body effects (FBEs) in vertical MOSFETs due to depletion isolation as the pillar thickness is reduced from 200 to 10 nm. For pillar thicknesses between 200–60 nm, the output characteristics with and without impact ionization are identical at a low drain bias and then diverge at a high drain bias. The critical drain bias Vdc for which the increased drain–current is observed is found to decrease with a reduction in pillar thickness. This is explained by the onset of FBEs at progressively lower values of the drain bias due to the merging of the drain depletion regions at the bottom of the pillar (depletion isolation). For pillar thicknesses between 60–10 nm, the output characteristics show the opposite behavior, namely, the critical drain bias increases with a reduction in pillar thickness. This is explained by a reduction in the severity of the FBEs due to the drain debiasing effect caused by the elevated body potential. Both depletion isolation and gate–gate coupling contribute to the drain–current for pillar thicknesses between 100–40 nm
- …