Interactions of oxygen with MoS2 crystals investigated at microscopic length scales

PhD Course in Materials Science and Nanotechnology

Friday November 18th, 2022
11 a.m.
Seminar room, U5 Building – via Roberto Cozzi 55, Milano

Lecturer: Robert Szoszkiewicz

Title: Interactions of oxygen with MoS2 crystals investigated at microscopic length scales

Abstract: For numerous applications of microscopic MoS2 crystals, particularly in flexible nanoelectronics, one must understand their oxidation reactions in air and water [1]. In this seminar, I will present some case studies of microscopic heat induced oxidation and oxidative etching performed on thick, mechanically exfoliated, geological 2H MoS2 crystals in air. I will discuss some particular reaction mechanisms and our efforts in detecting various forms of MoO3 oxides onto such surfaces. In order to do so, we combined various global and local measurements such as XPS, XAS, Raman and AFM (topography, friction, Kelvin Probe) on single microscopic MoS2 flakes [2,3]. To have a closer look into an atomistic level at one particular oxidation regime, we combined experimental results with DFT calculations, which have been performed by prof. Sergio Tosoni at University of Milan-Bicocca.

[1] R. Szoszkiewicz, Local interactions of atmospheric oxygen with MoS2 crystals, Materials, 14, 5979, 31 pages (2021).
[2] M. Rogala, S. Sokołowski, U. Ukegbu, A. Mierzwa and R. Szoszkiewicz, Direct identification of surface bound MoO3 on single MoS2 flakes heated in dry and humid air, Advanced Materials Interfaces, 2100328, 11 pages (2021);
[3] S. Sovizi, S. Tossoni, R. Szoszkiewicz, “Caught in the act”: formation of single (MoO3)n molecules within basal MoS2 planes during their oxidative etching, Nanoscale Advances (2022) DOI: 10.1039/d2na00374k