8,669 research outputs found
On the possibility of tunable-gap bilayer graphene FET
We explore the device potential of tunable-gap bilayer graphene FET
exploiting the possibility of opening a bandgap in bilayer graphene by applying
a vertical electric field via independent gate operation. We evaluate device
behavior using atomistic simulations based on the self-consistent solution of
the Poisson and Schroedinger equations within the NEGF formalism. We show that
the concept works, but bandgap opening is not strong enough to suppress
band-to-band tunneling in order to obtain a sufficiently large Ion/Ioff ratio
for CMOS device operation.Comment: 10 pages, 3 figures, submitted to IEEE ED
Simulation of Graphene Nanoribbon Field Effect Transistors
We present an atomistic three-dimensional simulation of graphene nanoribbon
field effect transistors (GNR-FETs), based on the self-consistent solution of
the 3D Poisson and Schroedinger equation with open boundary conditions within
the non-equilibrium Green's Function formalism and a tight-binding hamiltonian.
With respect to carbon nanotube FETs, GNR-FETs exhibit comparable performance,
reduced sensitivity on the variability of channel chirality, and similar
leakage problems due to band-to-band tunneling. Acceptable transistor
performance requires effective nanoribbon width of 1-2 nm, that could be
obtained with periodic etching patterns or stress patterns
A Three-dimensional simulation study of the performance of Carbon Nanotube Field Effect Transistors with doped reservoirs and realistic geometry
In this work, we simulate the expected device performance and the scaling
perspectives of Carbon nanotube Field Effect Transistors (CNT-FETs), with doped
source and drain extensions. The simulations are based on the self-consistent
solution of the 3D Poisson-Schroedinger equation with open boundary conditions,
within the Non-Equilibrium Green's Function formalism, where arbitrary gate
geometry and device architecture can be considered. The investigation of short
channel effects for different gate configurations and geometry parameters shows
that double gate devices offer quasi ideal subthreshold slope and DIBL without
extremely thin gate dielectrics. Exploration of devices with parallel CNTs show
that On currents per unit width can be significantly larger than the silicon
counterpart, while high-frequency performance is very promising.Comment: Submitted to IEEE TE
Atomistic quantum transport modeling of metal-graphene nanoribbon heterojunctions
We calculate quantum transport for metal-graphene nanoribbon heterojunctions
within the atomistic self-consistent Schr\"odinger/Poisson scheme. Attention is
paid on both the chemical aspects of the interface bonding as well the
one-dimensional electrostatics along the ribbon length. Band-bending and doping
effects strongly influence the transport properties, giving rise to conductance
asymmetries and a selective suppression of the subband formation. Junction
electrostatics and p-type characteristics drive the conduction mechanism in the
case of high work function Au, Pd and Pt electrodes, while contact resistance
becomes dominant in the case of Al.Comment: 4 pages, 5 figure
Strong mobility degradation in ideal graphene nanoribbons due to phonon scattering
We investigate the low-field phonon-limited mobility in armchair graphene
nanoribbons (GNRs) using full-band electron and phonon dispersion relations. We
show that lateral confinement suppresses the intrinsic mobility of GNRs to
values typical of common bulk semiconductors, and very far from the impressive
experiments on 2D graphene. Suspended GNRs with a width of 1 nm exhibit a
mobility close to 500 cm^2/Vs at room temperature, whereas if the same GNRs are
deposited on HfO2 mobility is further reduced to about 60 cm^2/Vs due to
surface phonons. We also show the occurrence of polaron formation, leading to
band gap renormalization of ~118 meV for 1 nm-wide armchair GNRs.Comment: 11 pages, 4 figure
Modeling of ballistic nanoscale metal-oxide-semiconductor field effect transisitor
http://www.gianlucafiori.org/articles/fiori_iannaccone_apl.pd
Ultra-low-voltage bilayer graphene tunnel FET
In this work, we propose the Bilayer Graphene Tunnel Field Effect Transistor
(BG-TFET) as a device suitable for fabrication and circuit integration with
present-day technology. It provides high Ion/Ioff ratio at ultra-low supply
voltage, without the limitations in terms of prohibitive lithography and
patterning requirements for circuit integration of graphene nanoribbons. Our
investigation is based on the solution of the coupled Poisson and Schroedinger
equations in three dimensions, within the Non-Equilibrium Green (NEGF)
formalism on a Tight Binding Hamiltonian. We show that the small achievable gap
of only few hundreds meV is still enough for promising TFET operation,
providing a large Ion/Ioff ratio in excess of 10^3 even for a supply voltage of
only 0.1 V. Key to this performance is the low quantum capacitance of bilayer
graphene, which permits to obtain an extremely small sub-threshold swing S
smaller than 20 mV/decade at room temperature.Comment: 10 pages, 3 figure
3D simulation of a silicon quantum dot in a magnetic field based on current spin density functional theory
http://www.gianlucafiori.org/articles/jocespin.pd
Study of sequential semileptonic decays of b hadrons produced at the Tevatron
We present a study of rates and kinematical properties of lepton pairs
contained in central jets with transverse energy E_T > 15 GeV that are produced
at the Fermilab Tevatron collider. We compare the data to a QCD prediction
based on the HERWIG and QQ Monte Carlo generator programs.We find that the data
are poorly described by the simulation, in which sequential semileptonic decays
of single b quarks (b --> l c X with c --> l s X) are the major source of such
lepton pairs.Comment: 25 pages, 8 figures. Some typos were fixed in the text and
bibliography. Submitted to Phys. Rev.
Semi-analytical model for Schottky-barrier carbon nanotube and graphene nanoribbon transistors
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