The effects of substitutional Fe-doping on magnetism in MoSand WSmonolayers.

Doping of two-dimensional (2D) semiconductors has been intensively studied toward modulating their electrical, optical, and magnetic properties. While ferromagnetic 2D semiconductors hold promise for future spintronics and valleytronics, the origin of ferromagnetism in 2D materials remains unclear. Here, we show that substitutional Fe-doping of MoSand WSmonolayers induce different magnetic properties. The Fe-doped monolayers are directly synthesized via chemical vapor deposition. In both cases, Fe substitutional doping is successfully achieved, as confirmed using scanning transmission electron microscopy. While both Fe:MoSand Fe:WSshow PL quenching and n-type doping, Fe dopants in WSmonolayers are found to assume deep-level trap states, in contrast to the case of Fe:MoS, where the states are found to be shallow. Usingm- and mm-precision local NVmagnetometry and superconducting quantum interference device, we discover that, unlike MoSmonolayers, WSmonolayers do not show a magnetic phase transition to ferromagnetism upon Fe-doping. The absence of ferromagnetism in Fe:WSis corroborated using density functional theory calculations.