575 research outputs found
Surface decorated silicon nanowires: a route to high-ZT thermoelectrics
Based on atomistic calculations of electron and phonon transport, we propose
to use surface decorated Silicon nanowires (SiNWs) for thermoelectric
applications. Two examples of surface decorations are studied to illustrate the
underlying deas: Nanotrees and alkyl functionalized SiNWs. For both systems we
find, (i) that the phonon conductance is significantly reduced compared to the
electronic conductance leading to high thermoelectric figure of merit, ,
and (ii) for ultra-thin wires surface decoration leads to significantly better
performance than surface disorder.Comment: Accepted for PR
Ab initio vibrations in nonequilibrium nanowires
We review recent results on electronic and thermal transport in two different
quasi one-dimensional systems: Silicon nanowires (SiNW) and atomic gold chains.
For SiNW's we compute the ballistic electronic and thermal transport properties
on equal footing, allowing us to make quantitative predictions for the
thermoelectric properties, while for the atomic gold chains we evaluate
microscopically the damping of the vibrations, due to the coupling of the chain
atoms to the modes in the bulk contacts. Both approaches are based on a
combination of density-functional theory, and nonequilibrium Green's functions.Comment: 16 pages, to appear in Progress in Nonequilibrium Green's Functions
IV (PNGF4), Eds. M. Bonitz and K. Baltzer, Glasgow, August 200
Electron- and phonon transport in silicon nanowires: an atomistic approach to thermoelectric properties
We compute both electron- and phonon transmissions in thin disordered silicon
nanowires. Our atomistic approach is based on tight-binding and empirical
potential descriptions of the electronic and phononic systems, respectively.
Surface disorder is modeled by including surface silicon vacancies. It is shown
that the average phonon- and electron transmissions through long SiNWs
containing many vacancies can be accurately estimated from the scattering
properties of the isolated vacancies using a recently proposed averaging method
[Phys. Rev. Lett. 99, 076803 (2007)]. We apply this averaging method to surface
disordered SiNWs in the diameter range 1-3 nm to compute the thermoelectric
figure of merit, ZT. It is found that the phonon transmission is affected more
by the vacancies than the electronic transmission leading to an increased
thermoelectric performance of disordered wires, in qualitative agreement with
recent experiments. The largest ZT>3 is found in strongly disordered
oriented wires with a diameter of 2 nm.Comment: 8 pages, 8 figure
Electronic transport properties of fullerene functionalized carbon nanotubes: Ab initio and tight-binding calculations
Fullerene functionalized carbon nanotubes—NanoBuds—form a novel class of hybrid carbon materials, which possesses many advantageous properties as compared to the pristine components. Here, we report a theoretical study of the electronic transport properties of these compounds. We use both ab initio techniques and tight-binding calculations to illustrate these materials’ transmission properties and give physical arguments to interpret the numerical results. Specifically, above the Fermi energy we find a strong reduction in electron transmission due to localized states in certain regions of the structure while below the Fermi energy all considered structures exhibit a high-transmission energy band with a geometry-dependent width.Peer reviewe
- …