Band structures and electronic properties of edge-functionalized germanene nanoribbons

Abstract

Free-standing germanene is a buckled 2D hexagonal semimetal with an intrinsic carrier mobility more than double that of graphene's. The germanene lattice allows for band gap opening via an applied electric field or adsorption of foreign atoms, enabling the creation of germanene based field-effect devices. While the formation of germanene nanoribbons has been shown to have a band gap, little research has been done on the electronic tunability of Ge nanoribbons. In this study, we analyzed the effect of H, C, P, As, S, Se, Te, F, Cl, Br, and I for edge-functionalization on the physical and electronic properties of germanene armchair (AGeNRs) and zigzag (ZGeNRs) nanoribbons. We found that the band gaps of AGeNRs are tunable through width and edge species, and alternate between semiconducting and semi-metallic. Through these methods the band gap can be tuned to any IR spectral band, while ZGeNRs are shown to be nodal semimetals at small atomic widths but transition to metallic behavior at large widths. This work indicates that the functionalized germanene nanoribbons are promising quantum materials with tunable band structures and electronic properties.