A comparison study on the electronic structures, lattice dynamics and thermoelectric properties of bulk silicon and silicon nanotubes

Abstract

In order to investigate the mechanism of the electron and phonon transport in a silicon nanotube (SiNT), the electronic structures, the lattice dynamics, and the thermoelectric properties of bulk silicon (bulk Si) and a SiNT have been calculated in this work using density functional theory and Boltzmann transport theory. Our results suggest that the thermal conductivity of a SiNT is reduced by a factor of 1, while its electrical conductivity is improved significantly, although the Seebeck coefficient is increased slightly as compared to those of the bulk Si. As a consequence, the figure of merit (ZT) of a SiNT at 1200 K is enhanced by 12 times from 0.08 for bulk Si to 1.10. The large enhancement in electrical conductivity originates from the largely increased density of states at the Fermi energy level and the obviously narrowed band gap. The significant reduction in thermal conductivity is ascribed to the remarkably suppressed phonon thermal conductivity caused by a weakened covalent bonding, a decreased phonon density of states, a reduced phonon vibration frequency, as well as a shortened mean free path of phonons. The other factors influencing the thermoelectric properties have also been studied from the perspective of electronic structures and lattice dynamics.

Thermoelectric transport calculation of Si nanoclusters with different geometric shapes

“…Calculation of the electronic structure, the lattice dynamics and the thermoelectric properties of the Si nanoclusters with different geometric shapes could refer to our previous work [12, 13]. Strict geometric optimisation of the fabricated models was conducted according to the standards of energy, force, stress and displacement.…”

“…Therefore, we attempt to provide a complete understanding of the electronic structure and the lattice dynamics of Si nanobox, Si nanocylinder, Si nanosphere and Si nanotetrahedron on the thermoelectric properties through first-principles calculation, lattice simulation and Boltzmann transport theory. Calculation of the electronic structure, the lattice dynamics and the thermoelectric properties of the Si nanoclusters with different geometric shapes could refer to our previous work [12,13]. Strict geometric optimisation of the fabricated models was conducted according to the standards of energy, force, stress and displacement.…”

Thermoelectric properties of Sr 0.61 Ba 0.39 Nb 2 O 6− δ ceramics in different oxygen-reduction conditions

“…The thermoelectric conversion efficiency is evaluated by the thermoelectric figure of merit ZT = S 2 T /ρκ, where S is the Seebeck coefficient, T is the absolute temperature, ρ is the electrical resistivity, and κ is the thermal conductivity. Although heavy-metal-based thermoelectric materials, such as (Bi, Sb) 2 (Te, Se) 3 , SiGe, PbTe, and relevant semiconductors, have been well studied, [1][2][3][4][5][6][7] there are some limitations, for instance, high costs, instability at high temperatures, and dependence on rare or toxic elements. [8][9][10] Oxide thermoelectric materials can solve these problems, [8,9] but the thermoelectric properties of oxide are still far from practical application.…”

Electron–acoustic phonon interaction and mobility in stressed rectangular silicon nanowires

“…The phonon properties which are relevant to the thermal and electric performance in semiconductor nanostructures, have attracted much scientific attention. [3][4][5][6][7] Through controlling and manipulating the phonon dispersion, the phonon group velocity, and the density of states, the phonon engineering approaches have been suggested to tune the thermal and electric properties of the nanostructures, for example, the phonon thermal conductivity and the electron-acoustic phonon interaction. [7][8][9][10] The electron-acoustic phonon interaction is of high interest since it inevitably influences the charge carrier mobility in the semiconductor nanostructures, which is linked to the performance of complementary metal-oxide-semiconductors (CMOS).…”