Hydrogen-assisted layer-by-layer growth and robust nontrivial topology of stanene films on Bi(111)

TL;DR

This study uses first-principles methods to elucidate the growth mechanisms and topological properties of few-layer stanene on Bi(111), highlighting hydrogen passivation's role in stabilizing high-quality films with robust quantum spin Hall effects.

Contribution

It reveals the atomistic growth process and the importance of hydrogen passivation in achieving layer-by-layer growth of topologically nontrivial stanene on Bi(111).

Findings

Hydrogen acts as a surfactant stabilizing stanene growth.

Robust quantum spin Hall effects are observed under various conditions.

Surface passivation is crucial for high-quality, layered stanene films.

Abstract

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.