Structure and Dynamics of Water Confined at the SiO₂/WS₂ Interface

Area of Science:

• Materials Science
• Surface Science
• Computational Chemistry

Background:

• Tungsten disulfide (WS2) possesses unique electronic properties, making it relevant for electronic applications.
• Silicon dioxide (SiO2) is a common dielectric substrate, frequently used in conjunction with 2D materials like WS2.
• The hydrophilic nature of SiO2 surfaces leads to water confinement at the WS2/SiO2 interface, impacting material behavior.

Purpose of the Study:

• To investigate the structural and dynamic properties of water confined between WS2 and SiO2.
• To compare confined water properties with water adsorbed on isolated WS2 and SiO2 surfaces.
• To understand the influence of silanol groups and WS2 on water behavior at the interface.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Ab initio molecular dynamics (AIMD) simulations.
• Comparative analysis of water structures and dynamics across different interfaces.

Main Results:

• Confined water exhibits increased structural ordering compared to bulk water.
• Water molecule orientation is dictated by hydrogen bonding with silanol groups and interaction with WS2 (H-up configuration).
• Silanol groups disrupt water hydrogen bonding networks, particularly at monolayer coverage.
• Structural and dynamic changes in water are layer-dependent.

Conclusions:

• The WS2/SiO2 interface significantly alters water structure and dynamics.
• Silanol groups and WS2 play crucial roles in mediating water behavior at the interface.
• Understanding confined water properties is essential for designing and optimizing WS2-based devices.