Germanene: the germanium analogue of graphene

Germanene, a monolayer allotrope of germanium atoms arranged in a honeycomb structure, is the germanium analogue of graphene. Here in this talk, I will show that two different ways to synthesis germanene. The deposition of several monolayers of Pt on Ge(110) followed by annealing at 1100 K results in the formation of three-dimensional eutectic GePt nanocrystals. Upon cooling down these eutectic GePt nanocrystals phase separate into pure Ge2Pt and Ge phases. The Ge segregrates towards the surface and forms a germanene layer and with a 2D Dirac signature. In the second part I will show the successful synthesis of germanene on molybdenum disulfide (MoS2), a band gap material. Preexisting defects in the MoS2 surface act as preferential nucleation sites for the germanene islands. The lattice constant of the germanene layer (3.8±0.2A) is about 20% larger than the lattice constant of the MoS2 substrate (3.16A). Scanning tunneling spectroscopy measurements and density functional theory calculations are in a good agreement revealing that the linearly dispersing bands at the K points.