Molybdenum sulphide: understanding surface-bulk excitations

PAULA BUITRAGO; S. MONTORO; S. RODRÍGUEZ; ALBANESI, E.A.; R. VIDAL; BONETTO, F

San Pablo

Conferencia; Autumn Meeting of the Brazilian Society of Physics 2022; 2022

Brazilian Society of Physics

Molybdenum sulphide (MoS2) is a semiconductor of the family of transition metal dichalcogenides (TMDC). By reducing the dimension of the material, the band gap can change from indirect (1.2 eV for bulk) to direct (1.9 eV for a monolayer). This particular feature makes it a promising candidate for nanoscale applications. Therefore, and in order to control the functionality of new technological nanostructures, it is essential to study its opto-electronic properties. Reflection Electron Energy Loss Spectroscopy (REELS) and Auger Electron Spectroscopy (AES), are highly surface sensitive techniques and provide relevant information on the response of solid state electrons to incident charged particles. In this study, we made a REELS analysis of MoS to recognise electronic losses due to collective oscillations generated on the sample surface. In addition, the study was complemented with AES analysis to identify stoichiometric changes generated by sputtering. First, the influence on the peaks signal intensity and the electronic distribution was examined by varying the angle of incidence of the electrons. After that, the REELS distributions at different primary electron energies were measured and compared. Thus, it is possible to link each electronic signal loss to different physical processes. All experiments were carried out under ultrahigh vacuum conditions and samples were checked to be free of surface contamination. Metallicmolybdenum was previously studied and used as a reference material.