Structural and electronic properties of functionalized germanene

Abstract

The study of two-dimensional (2D) materials has increasing interest after the discovery of graphene whose property differed surprisingly from its three-dimensional form. 2D materials have electrical properties of great interest for technological applications, and play a role in the reduction of the dimensions of the electronic devices that are currently produced as well. Graphene in its honeycomb structure has a zero gap, with conducing and valence bands being degenerate at K and K’ points, forming cones. However, difficulties in carrying out and adjusting a reasonable sizeable band gap in graphene is attracting increasing interest to other two-dimensional materials. One of the promising material is a single layer of germanium, the so-called germanene. Recent investigations suggest that germanium layers react rapidly with the environment. This may affect not only their electronic structure, but also their reactivity and optical properties. Therefore one may search for ways of tuning the electronic properties of these twodimensional layers. A promising route for tuning the electronic structure of bare layered materials is the adsorption of organic molecules or functional groups. Recently, germanene has been synthesized to create hybrid layers upon adsorption of organic ligands. In this work, band gap tuning of organic ligands adsorbed on bidimensional germanium monolayers have been investigated using first-principles calculations. We show that the adsorption of these small groups retains the initially stable free-standing pristine buckled germanium nanostructures. We claim that the stability of these structures stem from both strain induced by the adsorption of this organic group and ligand-ligand interactions. Our studies of a finite band gap form the way for a rational design of germanium nanostructures, which can find applications in electronic devices.