  It has been proposed for a long time now that the reduction of the thermal
conductivity by reducing the phonon mean free path is one of the best way to
improve the current performance of thermoelectrics. By measuring the thermal
conductance and thermal conductivity of nanowires and thin films, we show
different ways of increasing the phonon scattering from low temperature up to
room temperature experiments. It is shown that playing with the geometry
(constriction, periodic structures, nano-inclusions), from the ballistic to the
diffusive limit, the phonon thermal transport can be severely altered in single
crystalline semiconducting structures; the phonon mean free path being in
consequence reduced. The diverse implications on thermoelectric properties will
be eventually discussed.
