The fascinating electronic and optoelectronic properties of freestanding graphene and the possible inclusion of novel two-dimensional (2D) systems in silicon-based electronics have driven the search for atomic layers consisting of other group-IV elements Si, Ge, Sn, and Pb, which form similar hexagonal lattices and are isoelectronic to graphene. The resulting 2D crystals silicene, germanene, stanene and plumbene, referred as Xenes, but also their functionalized counterparts, e.g. the hydrogenated sheet crystals, named as Xanes, silicane, germanane, and stanane, are in the focus of this review article. In addition, halogenated Xenes are investigated. The consequences of the larger atomic radii on the atomic geometry, the energetic stability, and possible epitaxial preparations are discussed. In the case of honeycomb atomic arrangements, the low-energy electronic excitations are ruled by almost linear bands. Spin–orbit coupling opens small gaps leading to Dirac fermions with finite effective masses. The linear bands give rise to an absorbance of the Xenes determined by the finestructure constant in the long-wavelength regime. While for vanishing photon energies the excitonic influence is still an open question, saddle-point excitons and excitons at M0 van Hove singularities appear at higher frequencies. After opening substantial fundamental gaps by hy drogenation, the absorption edges of the Xanes, silicane, germanane, and stanane, are dominated by bound excitons with extremely large binding energies. Other chemical functionalizations, but also vertical electric fields, yield electronic structures ranging from topological to trivial in sulators. Even a quantum spin Hall phase is predicted at room temperature. The topological character and the possible quantization of the spin Hall conductivity are studied versus gap inversion, chemical functionalization, and Rashba spin–orbit interaction. The drastic changes of the electronic properties of Xenes with chemical functionalization, interaction with the substrate, and external perturbations, open future opportunities for tailoring fundamental properties and, therefore, interesting applications in novel electronic and optoelectronic nanodevices.

Bechstedt, F., Gori, P., Pulci, O. (2021). Beyond graphene: clean, hydrogenated and halogenated silicene, germanene, stanene, and plumbene. PROGRESS IN SURFACE SCIENCE, 96(3) [10.1016/j.progsurf.2021.100615].

Beyond graphene: clean, hydrogenated and halogenated silicene, germanene, stanene, and plumbene

Pulci O
2021-01-01

Abstract

The fascinating electronic and optoelectronic properties of freestanding graphene and the possible inclusion of novel two-dimensional (2D) systems in silicon-based electronics have driven the search for atomic layers consisting of other group-IV elements Si, Ge, Sn, and Pb, which form similar hexagonal lattices and are isoelectronic to graphene. The resulting 2D crystals silicene, germanene, stanene and plumbene, referred as Xenes, but also their functionalized counterparts, e.g. the hydrogenated sheet crystals, named as Xanes, silicane, germanane, and stanane, are in the focus of this review article. In addition, halogenated Xenes are investigated. The consequences of the larger atomic radii on the atomic geometry, the energetic stability, and possible epitaxial preparations are discussed. In the case of honeycomb atomic arrangements, the low-energy electronic excitations are ruled by almost linear bands. Spin–orbit coupling opens small gaps leading to Dirac fermions with finite effective masses. The linear bands give rise to an absorbance of the Xenes determined by the finestructure constant in the long-wavelength regime. While for vanishing photon energies the excitonic influence is still an open question, saddle-point excitons and excitons at M0 van Hove singularities appear at higher frequencies. After opening substantial fundamental gaps by hy drogenation, the absorption edges of the Xanes, silicane, germanane, and stanane, are dominated by bound excitons with extremely large binding energies. Other chemical functionalizations, but also vertical electric fields, yield electronic structures ranging from topological to trivial in sulators. Even a quantum spin Hall phase is predicted at room temperature. The topological character and the possible quantization of the spin Hall conductivity are studied versus gap inversion, chemical functionalization, and Rashba spin–orbit interaction. The drastic changes of the electronic properties of Xenes with chemical functionalization, interaction with the substrate, and external perturbations, open future opportunities for tailoring fundamental properties and, therefore, interesting applications in novel electronic and optoelectronic nanodevices.
2021
Pubblicato
Rilevanza internazionale
Articolo
Esperti anonimi
Settore FIS/03 - FISICA DELLA MATERIA
Settore PHYS-04/A - Fisica teorica della materia, modelli, metodi matematici e applicazioni
English
two-dimensional material; interaction with substrate; dirac electron; band topology; optical spectra; spin hall conductivity Exciton Electric field tuning
Bechstedt, F., Gori, P., Pulci, O. (2021). Beyond graphene: clean, hydrogenated and halogenated silicene, germanene, stanene, and plumbene. PROGRESS IN SURFACE SCIENCE, 96(3) [10.1016/j.progsurf.2021.100615].
Bechstedt, F; Gori, P; Pulci, O
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/289290
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