Adsorption of Organic Molecules on the Hydrogenated Germanene: A DFT Study

Graphene-like group IV semiconductors such as silicene and germanene may be organic functionalized to supply the necessary tools for the manipulations at a molecular level that the microelectronics industry will demand within the following years. In particular, the organic functionalization with molecules containing unsaturated C–C bonds by means of a radical-initiated reaction on hydrogenated surfaces constitutes a favorable route for the attachment of organic layers. In this work we have evaluated the organic functionalization of the hydrogenated germanene (H-germanene) with acetylene, ethylene, and styrene and compared these results with previous calculations made by us of the adsorption on the hydrogenated graphene surface (H-graphene) and on the hydrogenated silicene surface (H-silicene). Results toward organic functionalization from H-germanene and H-graphene are markedly different. On the H-germanene the adsorption of acetylene and ethylene is energetically favorable, while the adsorption of styrene, despite being energetically favorable, leads to a final state whose structure configuration does not favor a chain reaction. On the other hand, adsorption of these molecules on the H-graphene is less likely to occur with acetylene and ethylene, while for styrene it is not energetically favorable. These variations in surface reactivity between H-graphene and H-germanene are attributed to the larger lattice constant of H-germanene and differences in the electronegativity of C, Ge, and H atoms.