Hydrogenation of silicene on Ag(111) and formation of half-silicane

Abstract

Functionalization of silicene on metal substrates represents a key step for applications of silicene in future nanoelectronic devices. We find similarities in the electronic bands of 2√3 × 2√3R30° silicene and other silicene superstructures such as √13 × √13R13.9° and 4 × 4, that is, silicene π electrons lose their two-dimensional (2D) honeycomb character while σ states turn out to be less interacting and moderately affected. Half-silicane with a prefect 1 × 1 periodicity is formed on Ag(111), with one silicon sublattice accommodating the hydrogen atoms. Hydrogenation rearranges the out-of-plane buckling of silicene on Ag(111), and the energy of silicon σ states is raised toward the Fermi level (E_F) due to the change of the buckling configuration. The formation of half-silicane results in a new type of silicene monolayer with a large buckling height. Dehydrogenation occurs at moderate temperatures, demonstrating that such uniformly ordered and reversible hydrogenation may be useful for tuning the properties of silicene and for controllable hydrogen storage.