Abstract
Substitutional doping is one of the principal approaches used to control the electronic properties of layered transition-metal dichalcogenides. In this work, pristine and Nb-doped MoS 2 were comparatively investigated using low-energy electron diffraction, X-ray photoelectron spectroscopy, including valenceband measurements, and Raman spectroscopy. The LEED patterns show that the Nb-doped sample retains the characteristic hexagonal surface structure of MoS 2 , although the enhanced diffuse background and additional weak diffraction features indicate an increased degree of structural disorder or the presence of additional surface domains. Core-level XPS spectra confirm that the dominant Mo4+ – S2− chemical environment characteristic of MoS 2 is preserved, with no evidence of substantial surface oxidation or secondary sulfur-containing phases. The Nb 3d signal was not directly resolved, consistentwith the low nominal dopant concentration and the sensitivity limits of the XPS configuration employed. However, correlated shifts of the valence-band, Mo 3d, and S 2p features towards lower binding energy indicate an Nb-induced modification of the electronic structure, consistent with acceptor-type Nb incorporation into the MoS 2 host lattice. The Raman spectra of both samples exhibit the characteristic E12g and A1g modes, confirming that the vibrational structure of 2H- MoS 2 is retained after doping. Overall, low-level Nb doping modifies the electronic structure and increases structural disorder without causing large-scale disruption or phase transformation of the MoS 2 matrix.