A New Phase of Two-Dimensional Tin on Hexagonal Boron Nitride Monolayer on Metal

Monolayer tin (Sn) in the stanene form is expected to be a large bandgap two-dimensional (2D) topological insulator. However, electronic properties and growth morphology of Sn thin films highly depend on the supporting substrate. We compare the growth of Sn on a metal substrate with and without the hexagonal boron nitride (hBN) monolayer, which binds weakly to the substrate. Distinct growth morphologies, arising from the different interaction to substrate, are revealed by scanning tunneling microscopy. Most intriguingly, a new Sn phase corresponding to the √7 × √7 superlattice of the underlying metal surface is identified on the hBN/metal substrate, suggesting the influence of metal on Sn through the decoupling hBN monolayer, as our first-principles calculations support. Our study demonstrates that substrates provide a platform to significantly change the electronic and topological properties of 2D material.