Abstract Two-dimensional (2D) metallic transition-metal dichalcogenides (TMDCs), such as 1T-TiSe2, have recently emerged as unique platforms for exploring their exciting properties of superconductivity and the charge density wave (CDW). 2D 1T-TiSe2 undergoes rapid oxidation under ambient conditions, significantly affecting its CDW phase-transition behavior. We comprehensively investigate the oxidation process of 2D TiSe2 by tracking the evolution of the chemical composition and atomic structure with various microscopic and spectroscopic techniques and reveal its unique selenium-assisting oxidation mechanism. Our findings facilitate a better understanding of the chemistry of ultrathin TMDCs crystals, introduce an effective method to passivate their surfaces with capping layers, and thus open a way to further explore the functionality of these materials toward devices. The oxidation behavior and the effect of the oxidation on the charge density wave transition behavior of two-dimensional TiSe2 is revealed (see picture; Ti purple, Se yellow, O blue). This provides important insights into the oxidation mechanism of ultrathin layered materials, and paves the way for exploiting the unusual properties of these materials.
Published in: "Angewandte Chemie International Edition".