Interaction Modification of Transition Metal Dichalcogenide Layers by Halogenation

Density functional theory (DFT)-based numerical calculations have been performed for MoS2 and WS2 to achieve the fully relaxed, fully optimized systems, followed by the adsorption of F and Cl over the pristine MoS2 and WS2 bilayers. In order to check the electronic properties of the resulting systems, density of states (DOS) and band-structure calculations were performed. The resulting pristine and halide structures were then submitted to energy decomposition analysis (EDA) calculations to study the van der Waals interactions between the layers as the halogen adsorption occurs. Among other results, it was found that F weakens the van der Waals interactions more than Cl in MoS2, whereas the opposite happens for WS2. Also, the interactions in these systems are mainly maintained by electrostatic interactions rather than by dispersive van der Waals. Lastly, results show that halogenation weakens the van der Waals interactions more effectively on WS2 systems, suggesting that halogenation could be more effective for atomic layer etching (ALE) in WS2 rather than MoS2.