Structural and electronic properties of two-dimensional hydrogenated Xenes

Abstract

Structural and electronic properties of pristine two-dimensional group IV Xenes (X = C, Si, Ge, Sn, Pb) and hydrogenated Xenes are studied, using density functional theory (DFT) calculations with and without spin–orbit coupling (SOC). The pristine hexagonal monolayer Xenes show buckled structure upon relaxation except graphene. The buckling increases linearly from graphene to plumbene. The band structures without SOC of group-IV Xenes are semi-metallic. However, inclusion of SOC mainly opens the bandgap at the Dirac point. Semi hydrogenation leads to enhanced buckling in all Xenes which indicate a tendency towards more sp3 like structures. The electronic structures of semi hydrogenated Xenes do not show Dirac cones. Spin polarized band structures show magnetism with magnetic moment of 1.0 and all SH Xenes are magnetic semiconductor except SH plumbene. Full hydrogenation vanishes buckling upon relaxation and the structure becomes planar implying sp2-like hybridization. The band structures for fully hydrogenated Xenes turns out to be semiconducting and the Dirac cones also disappear. The bandgap changes from indirect to direct at FH stanene, while FH plumbene turns out to be semi-metallic. SOC gives rise to bandgap of 0.47 eV in FH plumbene, which is otherwise a semi-metal.