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

• Published in: Chinese physics B Vol. 22; no. 11; pp. 477 - 482
• Main Author: 路朋献 屈凌波 程巧换
• Format: Journal Article
• Language: English
• Published: 01.11.2013
• Subjects: Dynamic mechanical properties; Dynamic structural analysis; Dynamics; Electronic structure; Phonons; Silicon; Thermal conductivity; Thermoelectricity; 体硅; 变速器结构; 密度泛函理论; 晶格动力学; 热传导率; 热电性能; 电子结构; 硅纳米管
• ISSN: 1674-1056; 2058-3834; 1741-4199
• DOI: 10.1088/1674-1056/22/11/117101

In order to investigate the mechanism of the electron and phonon transport in a silicon nanotube （SiNT）, the elec- tronic 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.