  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.
