Theoretical characterisation of point defects on a MoS 2 monolayer by scanning tunnelling microscopy

C González (1, 2) , B Biel (2) , Yannick J. Dappe (1)

1 GMT - Groupe Modélisation et Théorie
2 UGR - Universidad de Granada = University of Granada

Different S and Mo vacancies as well as their corresponding antisite defects in a free-standing MoS 2 monolayer are analysed by means of scanning tunnelling microscopy (STM) simulations. Our theoretical methodology, based on the Keldysh nonequilibrium Green function formalism within the density functional theory (DFT) approach, is applied to simulate STM images for different voltages and tip heights. Combining the geometrical and electronic effects, all features of the different STM images can be explained, providing a valuable guide for future experiments. Our results confirm previous reports on S atom imaging, but also reveal a strong dependence on the applied bias for vacancies and antisite defects that include extra S atoms. By contrast, when additional Mo atoms cover the S vacancies, the MoS 2 gap vanishes and a bias-independent bright protrusion is obtained in the STM image. Finally, we show that the inclusion of these point defects promotes the emergence of reactive dangling bonds that may act as efficient adsorption sites for external adsorbates.

Keywords: STM; DFT; 2D materials; MoS2; defects

Domains: Physics [physics]

C González, B Biel, Yannick J. Dappe. Theoretical characterisation of point defects on a MoS 2 monolayer by scanning tunnelling microscopy. Nanotechnology, 2016, 27 (10), pp.105702. ⟨10.1088/0957-4484/27/10/105702⟩. ⟨cea-01490962⟩