39,003 research outputs found
Integrated atomistic process and device simulation of decananometre MOSFETs
In this paper we present a methodology for the integrated atomistic process and device simulation of decananometre MOSFETs. The atomistic process simulations were carried out using the kinetic Monte Carlo process simulator DADOS, which is now integrated into the Synopsys 3D process and device simulation suite Taurus. The device simulations were performed using the Glasgow 3D statistical atomistic simulator, which incorporates density gradient quantum corrections. The overall methodology is illustrated in the atomistic process and device simulation of a well behaved 35 nm physical gate length MOSFET reported by Toshiba
Electron transport in an open mesoscopic metallic ring
We study electron transport in a normal-metal ring modeled by the tight
binding lattice Hamiltonian, coupled to two electron reservoirs. First,
Buttiker's model of incorporating inelastic scattering, hence decoherence and
dissipation, has been extended by connecting each site of the open ring to
one-dimensional leads for uniform dephasing in the ring threaded by magnetic
flux. We show with this extension conductance remains symmetric under flux
reversal, and Aharonov-Bohm oscillations with changing magnetic flux reduce to
zero as a function of the decoherence parameter, thus indicating dephasing in
the ring. This extension enables us to find local chemical potential profiles
of the ring sites with changing magnetic flux and the decoherence parameter
analogously to the four probe measurement. The local electrochemical potential
oscillates in the ring sites because of quantum-interference effects. It
predicts that measured four-point resistance also fluctuates and even can be
negative. Then we point out the role of the closed ring's electronic
eigenstates in the persistent current around Fano antiresonances of an
asymmetric open ring for both ideal leads and tunnel barriers. Determining the
real eigenvalues of the non-Hermitian effective Hamiltonian of the ring, we
show that there exist discrete bound states in the continuum of scattering
states for the asymmetric ring even in the absence of magnetic flux. Our
approach involves quantum Langevin equations and non-equilibrium Green's
functions.Comment: 19 pages, 6 figure
Cosmic-Ray Heating of Molecular Gas in the Nuclear Disk: Low Star Formation Efficiency
Understanding the processes occurring in the nuclear disk of our Galaxy is
interesting in its own right, as part of the Milky Way Galaxy, but also because
it is the closest galactic nucleus. It has been more than two decades since it
was recognized that the general phenomenon of higher gas temperature in the
inner few hundred parsecs by comparison with local clouds in the disk of the
Galaxy. This is one of the least understood characteristics of giant molecular
clouds having a much higher gas temperature than dust temperature in the inner
few degrees of the Galactic center. We propose that an enhanced flux of
cosmic-ray electrons, as evidenced recently by a number of studies, are
responsible for directly heating the gas clouds in the nuclear disk, elevating
the temperature of molecular gas ( 75K) above the dust temperature
( 20K). In addition we report the detection of nonthermal radio emission
from Sgr B2-F based on low-frequency GMRT and VLA observations. The higher
ionization fraction and thermal energy due to the impact of nonthermal
electrons in star forming sites have important implications in slowing down
star formation in the nuclear disk of our galaxy and nuclei of galaxies.Comment: 12 pages, one figure, ApJL (in press
Time Dependent Effects and Transport Evidence for Phase Separation in La_{0.5}Ca_{0.5}MnO_{3}
The ground state of La_{1-x}Ca_{x}MnO_{3} changes from a ferromagnetic
metallic to an antiferromagnetic charge-ordered state as a function of Ca
concentration at x ~ 0.50. We present evidence from transport measurements on a
sample with x = 0.50 that the two phases can coexist, in agreement with other
observations of phase separation in these materials. We also observe that, by
applying and then removing a magnetic field to the mainly charge-ordered state
at some temperatures, we can "magnetically anneal" the charge order, resulting
in a higher zero-field resistivity. We also observe logarithmic time dependence
in both resistivity and magnetization after a field sweep at low temperatures.Comment: 9 pages, LATEX, 3 postscript figure
Quantum measurement of the degree of polarization of a light beam
We demonstrate a coherent quantum measurement for the determination of the
degree of polarization (DOP). This method allows to measure the DOP in the
presence of fast polarization state fluctuations, difficult to achieve with the
typically used polarimetric technique. A good precision of the DOP measurements
is obtained using 8 type II nonlinear crystals assembled for spatial walk-off
compensation.Comment: 4 pages, 3 figure
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