Fermi level shifting of CVD-grown MoS2 nanosheets by cobalt doping-driven charge transfer and systematic strain

Abstract

Precise control of the Fermi level in two-dimensional materials is critical for modulating their electronic structure, thereby facilitating their effective implementation in advanced electronic and optoelectronic applications. Here, we report on the role of cobalt doping in modulating the Fermi level of MoS2 synthesized by the chemical vapor deposition process. Raman spectroscopic results confirmed the presence of p-type dopants and tensile strain in the system through characteristic peak shifts. Photoluminescence studies reinforced the Raman findings by showing progressive quenching of excitonic emission and defect state evolution, consistent with Co-induced p-type doping. X-ray photoelectron spectroscopy validated Co substitution in the MoS2 lattice and provided quantitative insights into bonding states and dopant concentration. Furthermore, Kelvin probe force microscopy measurements demonstrated a clear increase in work function with increasing Co concentration, reflecting a Fermi level shift toward the valence band. These findings highlight the dual role of cobalt doping in inducing strain and charge transfer, thereby offering a tunable strategy for engineering the electronic properties of MoS2 for next-generation nanoelectronics and catalytic applications.