  Ever since the first successful synthesis of stanene via epitaxial growth,
numerous efforts have been devoted to improving its overall quality and
exploring its topological and other exotic properties under different growth
conditions. Here, using first-principles approaches, we reveal the atomistic
growth mechanisms and robust topological properties of few-layer stanene on
Bi(111). We first show that monolayer stanene grown on Bi(111) follows a highly
desirable nucleation-and-growth mechanism, characterized by attractive
interaction of the Sn adatoms. More importantly, we reveal that surface
passivation by the residual hydrogen is essential in achieving layer-by-layer
growth of high-quality few-layer stanene, with the hydrogen functioning as a
surfactant in stabilizing the growing films. Furthermore, we investigate
systematically the dependence of the topological properties of stanene on the
film thickness, hydrogen passivation, and substrate, and obtain robust quantum
spin Hall effects under diverse physical conditions. The robustness of the
nontrivial topology is attributable to the strong spin-orbit coupling of the Bi
substrate. The atomistic growth mechanisms and nontrivial topology of stanene
as presented here are also discussed in connection with recent experimental
findings.
