Abstract
In this work, ab initio calculations based on density functional theory and the Landauer formalism are carried out to investigate ballistic thermoelectric properties of nanoribbons (NRs). The zigzag-edged NRs are metallic, and they are not included in this study. The armchair NRs possess two types of edge symmetries depending on the number of atoms present in a row; odd-numbered NRs have mirror symmetry, whereas the even-numbered NRs have glide reflection symmetry. The armchair-edged NRs are dynamically stable and show semiconducting properties with varying band gap values in the infrared and visible regions. Detailed transport analyses show that the -type Seebeck coefficient and the power factor differ because of the structural symmetry, whereas the -type thermoelectric coefficients are not significantly influenced. It is shown that the phonon thermal conductance is reduced to a third of its two-dimensional value via nanostructuring. The -type Seebeck coefficient and the power factor for -phase are enhanced in NRs. We report that the -type value of NRs at 300 and 800 K are enhanced by factors of 4 and 3, respectively.
1 More- Received 5 June 2020
- Revised 27 October 2020
- Accepted 8 December 2020
DOI:https://doi.org/10.1103/PhysRevB.103.014104
©2021 American Physical Society