447 research outputs found
Towards Multi-Scale Modeling of Carbon Nanotube Transistors
Multiscale simulation approaches are needed in order to address scientific
and technological questions in the rapidly developing field of carbon nanotube
electronics. In this paper, we describe an effort underway to develop a
comprehensive capability for multiscale simulation of carbon nanotube
electronics. We focus in this paper on one element of that hierarchy, the
simulation of ballistic CNTFETs by self-consistently solving the Poisson and
Schrodinger equations using the non-equilibrium Greens function (NEGF)
formalism. The NEGF transport equation is solved at two levels: i) a
semi-empirical atomistic level using the pz orbitals of carbon atoms as the
basis, and ii) an atomistic mode space approach, which only treats a few
subbands in the tube-circumferential direction while retaining an atomistic
grid along the carrier transport direction. Simulation examples show that these
approaches describe quantum transport effects in nanotube transistors. The
paper concludes with a brief discussion of how these semi-empirical device
level simulations can be connected to ab initio, continuum, and circuit level
simulations in the multi-scale hierarchy
Multi‑scale simulations of two dimensional material based devices: the NanoTCAD ViDES suite
NanoTCAD ViDES (Versatile DEvice Simulator) is an open-source suite of computing codes aimed at assessing the operation
and the performance of nanoelectronic devices. It has served the computational nanoelectronic community for almost two
decades and it is freely available to researchers around the world in its website (http://vides.nanotcad.com), being employed
in hundreds of works by many electronic device simulation groups worldwide. We revise the code structure and its main
modules and we present the new features directed towards (i) multi-scale approaches exploiting ab-initio electron-structure
calculations, aiming at the exploitation of new physics in electronic devices, (ii) the inclusion of arbitrary heterostructures
of layered materials to devise original device architectures and operation, and (iii) the exploration of novel low-cost, green
technologies in the mesoscopic scale, as, e.g. printed electronics.UniversitĂ di Pisa within
the CRUI-CAREERC PEP2D (contract No. 770047Italian Ministry of Education and Research (MIUR) in the framework
of the FoReLab project (Departments of Excellence
Multi-scale approach to first-principles electron transport beyond 100 nm
Multi-scale computational approaches are important for studies of novel,
low-dimensional electronic devices since they are able to capture the different
length-scales involved in the device operation, and at the same time describe
critical parts such as surfaces, defects, interfaces, gates, and applied bias,
on a atomistic, quantum-chemical level. Here we present a multi-scale method
which enables calculations of electronic currents in two-dimensional devices
larger than 100 nm, where multiple perturbed regions described by density
functional theory (DFT) are embedded into an extended unperturbed region
described by a DFT-parametrized tight-binding model. We explain the details of
the method, provide examples, and point out the main challenges regarding its
practical implementation. Finally we apply it to study current propagation in
pristine, defected and nanoporous graphene devices, injected by chemically
accurate contacts simulating scanning tunneling microscopy probes
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