Surface morphology, magnetism and chemical state of Fe coverage on MoS2 substrate

The surface morphology, magnetism and chemical state of Fe coverage on the surface of molybdenum disulfide (MoS2) were investigated using scanning tunneling microscopy, magneto-optical Kerr effect, and depth-profiling X-ray photoemission spectroscopy (XPS). Fe deposition on the MoS2 substrate resulted in a nanoparticle array with the particle size ranged few nanometers (∼3±1 nm). For low-coverage Fe deposition <6 ML, nanoparticles were well-separated and long-range magnetic ordering was absent at room temperature. When the Fe coverage was increased, in-plane magnetic anisotropy was observed and the magnetic coercivity increased monotonically. The depth-profiling XPS showed the presence of a pure Fe state without observable chemical shift at the Fe/MoS2 interface. The XPS measurement of Pd/2 ML Fe/MoS2 also confirmed the dominance of the pure Fe state at the interface. The increase in Fe coverage changed the morphology from a nanoparticle array to a continuous coverage, leading to the onset of the ferromagnetic ordering and the transition from continuous surface oxidation to a bilayer structure.