Optical and Magnetic Properties of Fe-Infused 2D-MoS₂

Doping of two-dimensional (2D) transition metal dichalcogenides (TMDs) with magnetic impurities has generated significant interest for their potential applications as room temperature dilute magnetic semiconductors. In particular, iron-doped 2D-MoS₂ is interesting, as it has been reported to demonstrate diamagnetic, ferromagnetic, and paramagnetic behaviors. A key focus has been to understand whether their observed properties originate purely from the infused Fe atoms, or from defect/defect complexes in these systems. We present our results from simultaneous investigations of the structural, optical, and magnetic properties of mono- and multilayer 2D-Fe@MoS₂. Samples were synthesized by a chemical vapor deposition (CVD) system that allows controlled introduction of Fe atoms into the 2D structure of MoS₂. Aberration corrected high resolution scanning transmission electron microscopy (STEM), high-angle annular dark-field imaging (HAADF), and atomic force microscopy (AFM) were used to characterize the structure of these 2D materials from atoms-scale to nano- and micro-scales. Confocal Raman and photoluminescence (PL) mapping were employed to investigate the impact of Fe-infusion on the in-plane and out-of-plane vibrational modes, and the dynamics of the A-exciton and A-trion populations and their binding energies. Magnetic properties of these materials were investigated using magnetic force microscopy (MFM) and scanning nitrogen-vacancy center microscopy (SNVM). These experimental results suggest that while Fe infusion in our system led to sizable modification in the Raman and PL behavior, and MFM measurements appear to show phase-sensitive responses, no clear indication of ferromagnetic ordering could be found. We will discuss the nature of magnetism in Fe-doped MoS₂ based on our experimental observations and parallel theoretical modeling.