Reactivity Enhancement and Fingerprints of Point Defects on a MoS2 Monolayer Assessed by ab Initio Atomic Force Microscopy

The effect of topological point defects, vacancies, and substitutional antisites, in a monolayer MoS2, has been analyzed by ab initio atomic force microscopy (AFM) simulations. Our calculations based on density functional theory (DFT) show how a careful combination of measurements at different distances enables the characterization of each defect on the monolayer in future noncontact AFM experiments: Taking into account the minimum in the forces, atomic displacements, and charge transfer, a great enhancement has been found on the reactivity of MoS2 when some defects are included in the monolayer. We demonstrate the strong influence of the chemical composition of the tip and the environment of the chosen site on the calculated force. Furthermore, we show that the results can be mostly understood considering a standard metal semiconductor junction model. Finally, our study exhibits the possibility of local atomic doping using the AFM tip.