Transition Metal Dichalcogenides under Ion Irradiation: From Defects to Atomic Structure Engineering

We study the effects of ion irradiation on suspended MoS₂ monolayer (ML) by using molecular dynamics (MD) combined with density-functional theory (DFT) calculations. We systematically study the production of defects in a free-standing MoS₂ ML under noble gas ions bombardment for a broad range of incident angles and ion energies and determine the probabilities of producing single Mo and S vacancies. By comparing MD trajectories and analytical models for binary collision, we identified both direct and indirect mechanisms for defect production. Our results demonstrate that a selective sputtering of S atoms from the upper or lower layer can be achieved by choosing ion energy and incidence angle. The probability of producing S vacancy from upper layer increases by tilting the ion beam from the normal direction. The results showed that the defects cross section for both S and Mo vacancy grows with ion mass while the values for S vacancy are much higher than Mo vacancy. We further show the possibility of producing stable mixed MoSX (X from group V or VII) compounds with different electronic properties using ion irradiation. These findings suggest a promising route for post-growth processing of these materials for engineering electronic devices.