First germanium doped titanium disulfide polytypes Crystal structure and metal–metal interactions

Premier dopage au germanium de polytypes de disulfure de titane structure cristalline et interactions métal–métal

L. Hammoudi (1) , A. Gómez-Herrero (2) , M. Kars (1) , T. Roisnel (3) , L.C. Otero-Diáz (2)

1 USTHB - Université des Sciences et de la Technologie Houari Boumediene = University of Sciences and Technology Houari Boumediene [Alger]
2 UCM - Universidad Complutense de Madrid = Complutense University of Madrid [Madrid]
3 ISCR - Institut des Sciences Chimiques de Rennes

Single crystals of Ge-doped TiS2 polytypes, 1T, (4H)2, 12R, and their corresponding new a√3 × a√3 superstructure were grown by chemical vapor transport method. The crystals were characterized by combining X-ray diffraction and transmission electron microscopy techniques. The structures of these polytypes are all based on close packing layers of sulfur of CdI2-type structure. Except in the 1T polytype, the germanium atoms are observed to be equally distributed over both partial and complete occupancy layers. A significant distortion of the metal–sulfur distances is observed in the superstructure polytypes, as a consequence of metal–metal corrugated layers. The 12R-a√3 × a√3 superstructure is revealed by both electron diffraction and X-ray diffraction by the presence of satellite reflections. Electron diffraction patterns from the 12R polytype show highly structured diffuse scattering surrounding the main spots. These diffuse segments, which are arranged in triangles sharing vertices, correspond to a 2a* × 2a* superstructure and are attributed to the short-range order of metal atoms in the partially filled layers.

Keywords: Doped TiS2; X-ray diffraction; Superstructures; Germanium; Metal–metal interactions; Electron microscopy

Domains: Chemical Sciences

L. Hammoudi, A. Gómez-Herrero, M. Kars, T. Roisnel, L.C. Otero-Diáz. First germanium doped titanium disulfide polytypes Crystal structure and metal–metal interactions. Comptes Rendus. Chimie, 2019, 22 (5), pp.406-418. ⟨10.1016/j.crci.2019.04.006⟩. ⟨hal-02161843⟩