Epitaxial binding and strain effects of monolayer stanene on the Al$_{2}$O$_{3}$(0001) surface

TL;DR

This study uses first-principles calculations to explore how monolayer stanene interacts with an Al₂O₃ substrate, revealing its potential as a quantum spin Hall insulator and effects of fluorine decoration on its properties.

Contribution

It provides the first detailed analysis of epitaxial binding, strain effects, and electronic properties of stanene on Al₂O₃, including the impact of fluorine decoration.

Findings

Stanene strongly coherently strains and epitaxially binds to Al₂O₃.

Strained stanene on Al₂O₃ exhibits quantum spin Hall insulating behavior.

Fluorine decoration influences the binding and exfoliation potential of stanene.

Abstract

Stanene, the two-dimensional monolayer form of tin, has been predicted to be a 2D topological insulator due to its large spin--orbit interaction. However, a clear experimental demonstration of stanene's topologically nontrivial properties has eluded observation, in part because of the difficulty of choosing a substrate on which stanene will remain topologically nontrivial. In this paper, we present first-principles density functional theory (DFT) calculations of epitaxial monolayer stanene grown on the (0001) surface of alumina, Al$_{2}$O$_{3}$, as well as free-standing decorated stanene under strain. By describing the energetics and nature of how monolayer stanene binds to alumina, we show a strong energetic drive for the monolayer to be coherently strained and epitaxial to the substrate. By analyzing the electronic structure of strained stanene, we find it to be a quantum spin Hall insulator on Al$_{2}$O$_{3}$. We also describe the effect of \emph{in situ} fluorine decoration on the bound stanene monolayer, including on its potential for mechanical exfoliation.