Band structure, phonon spectrum, and thermoelectric properties of β-BiAs and β-BiSb monolayers

Abstract

First-principles calculation and Boltzmann transport theory have been combined to comparatively investigate the band structures, phonon spectra, lattice thermal conductivity, electronic transport properties, Seebeck coefficients, and figure of merits of both β-BiSb and β-BiAs monolayers. The calculation reveals that the addition of As and Sb atoms has an important effect in increasing and decreasing the band gap of the β-Bi monolayer, respectively, which should be mainly due to the interaction between the p-orbitals of Bi, As, and Sb atoms. It is also found that the phonon frequency, group velocity, phonon lifetime, and Grüneisen parameter (γ) should play dominant roles in determining the magnitude of the lattice thermal conductivity of β-BiSb and β-BiAs monolayers. Furthermore, the Seebeck coefficients and figure of merits of β-BiSb and β-BiAs monolayers are much bigger than those of β-Bi monolayers. The derived results are in good agreement with other theoretical results in the literature, and could provide a deep understanding of various properties of the binary monolayers.