Stability and electronic structure of two-dimensional allotropes of group-IV materials

Autor(es)

Matusalem, Filipe ; Marques, Marcelo ; Teles, Lara K. ; Bechstedt, Friedhelm

• Tipo de documento: Artigo Científico
• Fonte: PHYSICAL REVIEW B; v. 92, n. 4, p. 8-pg., 2015-07-29.

Resumo

We study six different two-dimensional (2D) allotropes of carbon, silicon, germanium, and tin by means of the ab initio density functional theory for the ground state and approximate methods to calculate their electronic structures, including quasiparticle effects. Four of the investigated allotropes are based on dumbbell geometries, one on a kagome lattice, and one on the graphenelike hexagonal structure for comparison. Concerning carbon, our calculations of the cohesive energies clearly show that the hexagonal structure (graphene) is most stable. However, in the case of Si and Ge, the dumbbell structures, particularly the large honeycomb dumbbell (LHD) geometries, are energetically favored compared to the sp(2)/sp(3)-bonded hexagonal lattice (i.e., silicene and germanene). The main reason for this is the opening of a band gap in the honeycomb dumbbell arrangements. The LHD sheet crystals represent indirect semiconductors with a K -> Gamma gap of about 0.5 eV. In the Sn case we predict the MoS2-like symmetry to be more stable, in contrast to the stanene and LHD geometries predicted in literature. Our results for freestanding group-IV layers shine new light on recent experimental studies of group-IV overlayers on various substrates. (AU)

• Processo FAPESP: 12/50738-3 - Estudo de pontos quânticos através de cálculos de primeiros princípios
• Beneficiário: Ronaldo Rodrigues Pelá
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 14/13907-7 - Propriedades físicas de materiais bidimensionais
• Beneficiário: Lara Kühl Teles
• Modalidade de apoio: Auxílio à Pesquisa - Pesquisador Visitante - Internacional