Two-dimensional hexagonal tin: Ab initio geometry, stability, electronic structure and functionalization

We study the structural, mechanical and electronic properties of the twodimensional (2D) allotrope of tin: tinene/stanene using first-principles calculation within density functional theory, implemented in a set of computer codes. Continuing the trend of the group-IV 2D materials graphene, silicene and germanene; tinene is predicted to have a honeycomb lattice with lattice parameter of a<inf>0</inf> = 4.62Å and a buckling of d<inf>0</inf> = 0.92. The electronic dispersion shows a Dirac cone with zero gap at the Fermi energy and a Fermi velocity of ρF = 0.97 × 10⁶ ms^-1; including spin-orbit coupling yields a bandgap of 0.10 eV. The monolayer is thermally stable up to 700 K, as indicated by firstprinciples molecular dynamics, and has a phonon dispersion without imaginary frequencies. We explore applied electric field and applied strain as functionalization mechanisms. Combining these two mechanisms allows for an induced bandgap up to 0.21 eV, whilst retaining the linear dispersion, albeit with degraded electronic transport parameters