Oxidation and defects in WS2 and WSe2: The first-principle analysis of their monolayer and bulk structures

Transition metal dichalcogenides (TMDs) have attracted considerable interest owing to their distinctive properties. Environmental stability and defects in these materials play a decisive role in modern devices. Exposure to water and other atmospheric elements leads to the development of defects that undermine their stability. We aimed to comprehend the sensitivity of WS2 and WSe2 to exposure to the oxygen (O) or hydroxyl (OH) group. Significant focus is directed towards the substitutional doping effect of O or OH on the chalcogen site, aiming to acquire data on binding energy (Eb), effective band structures (EBS), and density of states (DOS) through density functional theory (DFT) calculations. Calculated binding energy and molecular dynamics (MD) simulation indicate that O or OH can be effectively incorporated into the TMD lattice, even at higher concentrations, thus highlighting the thermal stability and structural flexibility of WS2 and WSe2. However, the band gap measurements suggest that the intrinsic optical properties remain stable in response to these dopants. In contrast, O or OH created distinct defect states, influencing their electronic properties. The analysis of partial density of states (PDOS) and partial effective band structures (PEBS) support the reliability and coherence of our computational approaches. The findings demonstrated that EBS and PEBS offer a more accurate representation of electronic states and reveal hidden characteristics (defect levels and localized states) that traditional approaches might overlook.