We investigated the epitaxial growth of single-layer molybdenum disulfide (MoS2) on graphene/Ir(111), aiming to understand its steps and mechanism and verify the stability of the heterostructure. By means of high-resolution X-ray photoelectron spectroscopy, we have revealed that accurate temperature control is crucial in allowing the formation and avoiding the degradation of single-layer MoS2 on graphene. We observed that keeping the substrate temperature T>800 K during the growth promotes efficient sulfur intercalation under graphene and the dissolution of sulfur in the Ir bulk, two processes that have been targeted as ones mainly responsible for irreversible degradation of the MoS2 single layer on graphene. We believe that these results could be instrumental in understanding and improving the epitaxial growth protocols for the growth of heterostructures combining epitaxial graphene and transition-metal dichalcogenides.
