Electronic structure, lattice dynamics and thermoelectric properties of silicon nanosphere-nanoribbon layered structure from first-principles calculation

How to further optimize the thermoelectric figure of merit of silicon (Si) nanostructure? Constructing the layered structure composed of two different Si nano morphologies should be viewed an effective approach. The figure of merit of the layered structure could be further optimized by tuning the different contribution from the composed nano morphologies on the electron and phonon transport. In order to reveal the thermoelectric transport mechanism, the electronic structure, the lattice dynamics and the thermoelectric properties of Si nanosphere, Si nanoribbon and the layered structure composed of the two nano morphologies were investigated through first-principles calculation, lattice dynamics simulation and Boltzmann transport theory. The results suggest that the figure of merit of the layered structure is improved significantly in whole although its specific thermoelectric parameters are unsatisfactory as compared to the single nano morphologies. Therefore we provide a complete understanding on the thermoelectric transport of the layered structure and an effective route to further optimize the figure of merit of Si nanostructure.