Engineering magnetic correlations in 2D tungsten diselenide via in situ adatom doping of Nb.

Heteroatom doping is a potential strategy for tailoring the electronic and optoelectronic properties of 2D transition metal dichalcogenides (TMDs). Conventional doping techniques employing elemental substitution are often constrained by factors such as lattice strain and phase instability. In this work, we develop a novel doping strategy implemented through in situ adatom engineering where the strong ionicity in TMDs facilitates charge transfer from the adatoms leading to modulation of carrier concentration in 2D TMDs. This is demonstrated using in situ addition of Nb adatoms on the surface of monolayer WSe2 during chemical vapour deposition growth which resulted in n-doping in WSe2 and Fano resonances due to enhanced electron-phonon interactions. The electron transfer from Nb adatoms generated localized magnetic moments in WSe2 at low doping, while competing interactions between spins at higher concentrations drives the system into a spin cluster glass like system. These observations are further supported through spin-polarized DFT calculations and charge transfer analysis. Our work demonstrates a new route to controllably grow doped 2D TMDs and 2D dilute magnetic semiconductors offering great promise for spintronic applications based on 2D materials.