Germanene, Stanene and other 2D materials

Germanene and stanene (also sometimes written stannene or called tinene) are 2D materials composed of germanium and tin atoms respectively arranged in a honeycomb structure similarly to graphene and silicene. The atomic structure of freestanding germanene and stanene is buckled like in the case of silicene (see Figure 2.4). DFT calculations (Kresse and Joubert, Phys Rev B 59:1758–1775, 1999) performed by projector augmented wave (PAW) method (Blöchl, Phys Rev B 50:17953–17979, 1994) and adopting PBE functional (Perdew et al. Phys Rev Lett 77:3865–3868, 1996) result in a lattice constants 4.06 and 4.67 Å and buckling heights of 0.69 and 0.85 Å for germanene and stanene respectively. The structure of germanene was first theoretically proposed together with that of silicene (Takeda and Shiraishi, Phys Rev B 50:14916–14922, 1994) while stanene was explored later (Cahangirov et al. Phys Rev Lett 102:236804, 2009, Sahin et al. Phys Rev B 80:155453, 2009, Xu et al. Phys Rev Lett 111:136804, 2013b)