Band structural and absorption characteristics of antimonene/bismuthene monolayer heterojunction calculated by first-principles

The band gap of lateral heterojunctions (LHSs) can be continuously tuned by changing the widths of their components. In this work, Sb/Bi LHSs based on monolayer Sb and Bi atoms with armchair and zigzag interfaces are constructed, respectively. It exhibits an atom's number in planner-dependent tunable band gap and near-infrared range absorption characteristics. They are systematically studied by first-principles calculations. The widths are represented by the number (n) of Sb or Bi atom chains. When n increases from 2 to 8, the bandgaps of armchair Sb-n/Bi-n LHSs decrease from 0.89 to 0.67 eV, and the band gaps of zigzag Sb-n/Bi-n LHSs decrease from 0.92 to 0.76 eV. The partial density of states spectra indicate that the occupied states of the valence band are mainly provided by the Bi 6p orbitals. Additionally, the unoccupied states of the conduction band are always provided by the Sb 5p orbitals and Bi 6p orbitals. For Sb-n/Bi-n LHSs, the absorption edge along XX and YY directions move toward the long wavelength direction. These results provide an approach for the applications of two-dimensional materials in near-infrared devices.