Epitaxial binding and strain effects of monolayer stanene on the Al${}_2$O${}_3$(0001) surface

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.

23 pages, 9 figures

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