Molybdenum sulphide: understanding surface-bulk excitations.

PAULA BUITRAGO; SILVIA MONTORO; SINDY JULIETH RODRÍGUEZ SOTELO; ALBANESI, EDUARDO ALDO; RICARDO VIDAL; FERNANDO BONETTO

Sao Paulo

Encuentro; Encontro de Outono 2022 da Sociedade Brasileira de Física.; 2022

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 partic ular 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 tech niques and provide relevant information on the response of solid state electrons to incident charged particles. In this study, we made a REELS analysis of MoS2 to recog nise 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. Metallic molybdenum was previously studied and used as a reference material.