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O: Fachverband Oberflächenphysik

O 111: Nanostructured Surfaces and Thin Films II: 1D and 2D Systems (joint session O/CPP)

O 111.1: Vortrag

Donnerstag, 19. März 2020, 15:00–15:15, WIL B321

Edges in group-IV monochalcogenides: stability and electronic properties — •Mahdi Ghorbani-Asl and Arkady V. Krasheninnikov — Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany.

The group-IV monochalcogenides including tin sulfide (SnS) and germanium sulfide (GeS) are layered semiconductors with an anisotropic crystal structure giving rise to several unusual physical properties. In this study, based on density functional theory combined with different dispersion corrections, we systematically investigated the structure, stability and electronic properties of monolayer and multilayer SnS and GeS with various possible stoichiometric and nonstoichiometric terminations of the edges. It was found that the (110) facet has the lowest energy and it is thus expected to be the most stable edge. We further demonstrated that nonstoichiometric edges can exist as they provide reconstructed structure or covalent interlayer coupling between layers, which lowers the formation energies of the edges. The results indicate that the stability of the edges generally decreases for higher facet indices. The electronic structure calculations showed that most of the studied compounds are semiconductors with a band gap in the range of 0.2 - 1.6 eV, depending on the crystallographic direction of the edge and its chemical termination. For both GeS and SnS nanoribbons, the band gap is smallest in the case of the (010) edge and largest for the (110) edge. The edge states are more pronounced in multilayer than monolayer nanoribbons.