Substrate effects of two-dimensional materials on few-layer antimony

A free-standing four-bilayer Sb (111) film exists a large energy gap due to the quantum tunneling between the two surfaces. The gap can vanish, and the spin-split surface states can be induced as a result of the suppression of the tunneling-induced coupling when the thin film is deposited on a substrate. In this chapter, we investigate Sb (111) films in contact with a single layer of Bi with and without defects by using density functional calculations. The stacking configurations between Sb films and substrates are also taken into account. The binding energy has a certain relation to the charge transfer of Sb films and substrates. Finally, we choose the h-BN as the substrate to compare the results of pure and boron-doped graphene. The substrate with defects, such as Bi monolayer, still induces the topological conduction of the composite structure. Similar features can also be observed in a three-bilayer Sb film in contact with B-doped graphene from the concentration of 1/24 to BC3. When the Sb film is in bridge-site contact with BC3, topological conduction can be switched between one-mode and two-mode transport by adjusting gate voltage, with the former being 100% spin-polarized and the latter being either unpolarized or completely polarized.