Activity Report 2010 - CNRS

SCIENTIFIC REPORT
FURTHER READING:
Phys. Rev. B (2011) - accepted
Thermoelectric transport properties of
silicon: Towards an ab initio approach
Appl. Phys. Lett. 94, 203109 (2009).
Improved thermoelectric properties of
Mg 2Si xGe ySn 1-x-y nanoparticle in alloy
materials.
Photovoltaic, in particular for organic
systems or for molecular photochemical
system (where the energy conversion
takes place in a single molecule),
represents also a new orientation with an
interesting synergy among theorists of
simulation. It actually appears that all
competences needed to tackle the four
aspects of a photovoltaic device (as
described in Figure 3) are present among
NanoSTAR project members.
Fig. 3: The different steps of a photovoltaic
device with a pn junction.
Chair of Excellence 2010: Harold
BARANGER
Coordinator: Mireille LAVAGNA
(INAC/SPSMS).
The so-called CORTRANO project focuses
on novel correlations that can be probed
in nanoscale systems, and their influence
on electronic transport or other nonequilibrium
observables. A strong link
between computational, analytical and
model approaches will be implemented to
tackle several problems in this field, i.e
steady-state quantum transport,
correlation and conductance in strongly
inhomogeneous low-density electron gas
or correlations induced on the fly by
localized impurities in particular in the
Josephson junction context.
Thermal properties
“New comers” Project 2007: Natalio
MINGO (Liten)
Post-doc fellow: Shidong WANG
Thermal properties and in particular heat
conduction are important in the contexts
of electronics (heat dissipation) and
energy conversion (thermoelectric
devices).
This project’s challenge precisely consists
in mastering thermal properties of such a
system.
In the context of thermoelectric
applications the aim is to get a system
which behaves simultaneously as a
crystal for electrons and as a glass for
phonons. Different systems have been
studied to reduce heat conduction
without destroying electrical conduction
in order to get a good factor of merit Z.
One of the strategies employed here is to
introduce nanoparticle or produce
nanocomposites to obtain ‘NEAT’
materials (‘Nanoparticle Embedded in
Alloy Thermoelectric’ materials).
(see Figure 4).
For example simulation showed that
Mg 2 Si x Ge y Sn 1-x-y alloys with embedded
Mg 2 Si nanoparticles are promising
thermoelectrics to be operated at
intermediate temperature. A design of a
new thermoelectric device based on semi
randomly dispersed wires has also been
proposed. This is the object of a patent
application. The invention allows to
considerably simplifying the fabrication
procedure for planar thermoelectric
devices. Shidong WANG, the postdoctoral
fellow employed by the
Foundation as part of this project,
performed calculations to assess the
robustness of the approach as well as its
feasibility.
Please read the corresponding Highlight
at the end of this report for further
information
Fig. 4: The heat conduction and thermoelectric properties of system (here SiGe) can be modified
by introducing nanodots which scatter phonons and reduce heat conductivity.
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