436 research outputs found
Shrinking limits of silicon MOSFET's: Numerical study of 10-nm-scale devices
We have performed numerical modeling of dual-gate ballistic n-MOSFET's with
channel length of the order of 10 nm, including the effects of quantum
tunneling along the channel and through the gate oxide. Our analysis includes a
self-consistent solution of the full (two-dimensional) electrostatic problem,
with account of electric field penetration into the heavily-doped electrodes.
The results show that transistors with channel length as small as 8 nm can
exhibit either a transconductance up to 4,000 mS/mm or gate modulation of
current by more than 8 orders of magnitude, depending on the gate oxide
thickness. These characteristics make the devices satisfactory for logic and
memory applications, respectively, though their gate threshold voltage is
rather sensitive to nanometer-scale variations in the channel length.Comment: 8 pages, 10 figures. Submitted to Special Issue of Superlattices and
Microstructures: Third NASA Workshop on Device Modeling, August 199
Activation of latent ribonuclease in the fat-body of fleshfly (Sarcophaga peregrina) larvae on pupation
Two Dimensional Quantum Mechanical Modeling of Nanotransistors
Quantization in the inversion layer and phase coherent transport are
anticipated to have significant impact on device performance in 'ballistic'
nanoscale transistors. While the role of some quantum effects have been
analyzed qualitatively using simple one dimensional ballistic models, two
dimensional (2D) quantum mechanical simulation is important for quantitative
results. In this paper, we present a framework for 2D quantum mechanical
simulation of a nanotransistor / Metal Oxide Field Effect Transistor (MOSFET).
This framework consists of the non equilibrium Green's function equations
solved self-consistently with Poisson's equation. Solution of this set of
equations is computationally intensive. An efficient algorithm to calculate the
quantum mechanical 2D electron density has been developed. The method presented
is comprehensive in that treatment includes the three open boundary conditions,
where the narrow channel region opens into physically broad source, drain and
gate regions. Results are presented for (i) drain current versus drain and gate
voltages, (ii) comparison to results from Medici, and (iii) gate tunneling
current, using 2D potential profiles. Methods to reduce the gate leakage
current are also discussed based on simulation results.Comment: 12 figures. Journal of Applied Physics (to appear
Investigation of marmoset hybrids (Cebuella pygmaea x Callithrix jacchus) and related Callitrichinae (Platyrrhini) by cross-species chromosome painting and comparative genomic hybridization
We report on the cytogenetics of twin offspring from an interspecies cross in marmosets (Callitrichinae, Platyrrhini), resulting from a pairing between a female Common marmoset (Callithrix jacchus, 2n = 46) and a male Pygmy marmoset (Cebuella pygmaea, 2n = 44). We analyzed their karyotypes by multi-directional chromosome painting employing human, Saguinus oedipus and Lagothrix lagothricha chromosome-specific probes. Both hybrid individuals had a karyotype with a diploid chromosome number of 2n = 45. As a complementary tool, interspecies comparative genomic hybridization (iCGH) was performed in order to screen for genomic imbalances between the hybrids and their parental species, and between Callithrix argentata and S. oedipus, respectively. Copyright (C) 2005 S. Karger AG, Basel
Evidence for an increase in positive surface charge and an increase in susceptibility to trypsin of Sarcophaga lectin (from the flesh fly, Sarcophaga peregrina) on its interaction with galactose, a hapten sugar of the lectin
Electronic States in Silicon Quantum Dots: Multivalley Artificial Atoms
Electronic states in silicon quantum dots are examined theoretically, taking
into account a multivalley structure of the conduction band. We find that (i)
exchange interaction hardly works between electrons in different valleys. In
consequence electrons occupy the lowest level in different valleys in the
absence of Hund's coupling when the dot size is less than 10 nm. High-spin
states are easily realized by applying a small magnetic field. (ii) When the
dot size is much larger, the electron-electron interaction becomes relevant in
determining the electronic states. Electrons are accommodated in a valley,
making the highest spin, to gain the exchange energy. (iii) In the presence of
intervalley scattering, degenerate levels in different valleys are split. This
could result in low-spin states. These spin states in multivalley artificial
atoms can be observed by looking at the magnetic-field dependence of peak
positions in the Coulomb oscillation.Comment: 18 pages, 5 figure
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