title: Stability and electronic properties of ultrathin films of silicon and germanium.
abstract: Recent studies have examined the possibility of growing honeycomb silicene and germanene, the silicon and germanium analogues of graphene. Here we use first-principles calculations to examine the relative stability of a number of other single-layer structures that are derived from prominent surface reconstructions of group-IV semiconductors. We find that Si single-layers with the geometry of the √3 × √3 reconstruction are more stable than honeycomb silicene. Likewise, honeycomb germanene is less stable than germanium ultrathin films with a √3 × √3 or 7 × 7 arrangement. √3 × √3 Si and Ge single layers are metals with strong peaks at the Fermi level, and, in the case of Ge, they bear a magnetic moment. Overall, the results demonstrate that free-standing Si and Ge nano-sheets differ in key structural and electronic properties from graphene, and may thus provide systems with alternative functionalities.
authors.affiliation: Department of Physics, National Technical University of Athens, Athens, Greece. kaltsasd@gmail.com
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Kaltsas
authors.forename: Leonidas
authors.initials: L
authors.lastname: Tsetseris