Impact of Confined Water on the Electronic Structure of the SiO₂ and WS₂ Interface

WS₂/SiO₂ heterostructures are commonly used in the production of field effect transistors, sensors and other devices. It is difficult to remove the water present on the SiO₂ surface during the fabrication process. Using density functional theory simulations, we investigate how confinement between SiO₂ and WS₂ layers affects the water properties and how the presence of water affects the properties of WS₂ film. Using ab initio molecular dynamics simulations we found that the confined water remains mobile but is structured by the interaction with WS₂ and SiO₂ with water protons drawn closer to both surfaces. The presence of 1-3 water layers does not significantly affect the band alignment between SiO₂ and WS₂ and the electronic properties of the WS₂ monolayer. However, in-gap states caused by the dynamic rearrangement of water molecules could cause reduction of electron and hole mobility in the WS₂ layers. This study provides insights into the impact of water on the electronic properties of WS₂ under different environmental conditions.