Thermoelectric properties of antimony films: roles of oxidation and topological quantum state

Motivated by interesting physical and chemical properties created by doping and topological quantum state, we perform the density functional theory and the Boltzmann transport equation to systematically investigate the geometric structures, stabilities, electronic structures, thermal conductivities and thermoelectric properties for Sb and its oxidations (Sb₂O and SbO). The predicted lattice thermal conductivity (k _L) of Sb is 11.6 nW K⁻¹ at 300 K, but it would fall drastically when introducing O atoms. This is mainly attributed to the strong anharmonic interactions by adding O atoms, and few contributions are from the decreasing phonon group velocities caused by the compressed phonon spectrum. SbO has been proven as a topological insulator with a relatively large topological band gap (E _g) ∼ 0.156 eV, and meanwhile its carrier mobilities (345.78 cm²/Vs for electrons) and scattering time (44.27 × 10⁻¹⁴ s for electrons) are also rather high among all 2D materials, exhibiting the excellent thermoelectric performance. The calculated maximum thermoelectric figure of merit ($Z{T}_{max}$) of the three Sb films for optimum n-type doping are close to each other at 300 K, but with an increasing temperature, the $Z{T}_{max}$ of Sb for optimum n-type doping climbs quickly and can reach up to 0.73 at 700 K, which is far higher than others. More interestingly, the $Z{T}_{max}$ of SbO can be increased sharply at 300 K after considering spin–orbit coupling (SOC): 0.50 for optimum p-type doping and 0.41 for optimum n-type doping. However, only the tiny changes in the $Z{T}_{max}$ of Sb can be found before and after considering SOC. Our research reveals how the doping and the topological quantum state affect thermoelectric performances, providing reference to design and search high $Z{T}_{max}$ thermoelectric materials in future. (paper)