Anisotropic electron delocalization dynamics induced by chlorine doping in CVD-grown MoS₂ monolayers

Chemical doping plays a pivotal role in tailoring the charge transport properties of two-dimensional transition metal dichalcogenides for nanoelectronic and optoelectronic applications. In this study, we examine the influence of chlorine doping on the local electronic structure and ultrafast electron dynamics of chemical vapor deposition (CVD)-grown monolayer MoS₂. Raman and photoluminescence (PL) spectroscopy, supported by X-ray photoelectron spectroscopy (XPS), reveal spectral shifts and core-level modifications consistent with n-type doping induced by Cl atoms. XPS further confirms that Cl efficiently passivates sulfur vacancies in the MoS₂ lattice. A ∼50% PL quenching upon doping indicates enhanced non-radiative recombination. To probe charge delocalization, we employ the core-hole clock (CHC) method by combining sulfur K-edge X-ray absorption with resonant Auger spectroscopy, using the S 1s core-hole lifetime as a femtosecond time reference. Electron delocalization time for in-plane S 3p_x,y states decrease from 1.42 fs to 0.63 fs upon Cl doping, while it increases from 0.58 fs to 0.84 fs for out-of-plane S 3p_z states. This anisotropic behavior highlights a strong orbital-selective tuning of charge transfer dynamics. Our results demonstrate that Cl doping modulates interlayer and intralayer interactions in MoS₂, enabling directional control over electron delocalization an essential aspect for designing next-generation 2D semiconductor devices.