Ti vacancies on the (001) surface of TiS2 detected by scanning tunneling microscopy: A combined experimental and theoretical study

E. Amzallag , Hervé Martinez (1) , Isabelle Baraille (1) , Michel Rérat (1) , Michel Loudet (1) , Danielle Gonbeau (1)

1 IPREM - Institut des sciences analytiques et de physico-chimie pour l'environnement et les materiaux

Various defects - either bright or dark triangular defects - are observed on the titanium disulfide surface (001) by ultra high vacuum scanning tunneling microscopy. The experimental interpretations of the images available in the literature suggest that a fraction of Ti atoms could be displaced from the octahedral site they occupied to vacant sites of the crystal structure, leading to more or less correlated defects. In this paper, we have performed ab initio periodic LCAO-B3LYP calculations on a (5 × 5) biperiodic supercell to model the electronic and geometrical involvements of Ti vacancies and to generate the theoretical STM images within the Tersoff-Hamann approximation. The relaxed structure of the Ti vacancy shows an inward movement of the neighboring sulfur atoms at the surface. However, the occupied vacancy electronic states at the Fermi level are mainly developed on the atomic orbitals of the first S neighbors at the surface, leading to bright triangular zones on the simulated image.

Mots clés: Titanium compounds; Scanning tunneling microscopy (STM); Surface defect; Ab initio; Computational geometry; Computer simulation; Crystal structure; density functional calculations; Density functional theory; Disulfur titanium; Electronic states; Scanning tunneling microscopy; Vacancy

Domaines: Chimie; Matériaux

E. Amzallag, Hervé Martinez, Isabelle Baraille, Michel Rérat, Michel Loudet, et al.. Ti vacancies on the (001) surface of TiS2 detected by scanning tunneling microscopy: A combined experimental and theoretical study. Solid State Sciences, 2007, 9 (7), pp.594-599. ⟨10.1016/j.solidstatesciences.2007.04.010⟩. ⟨hal-01498392⟩