Synthesis and Transport Properties of Degenerate P-Type Nb-Doped WS2 Monolayers

Substitutional doping has been proven to be an effective route to engineer band gap, transport characteristics, and magnetism in transition metal dichalcogenides. Herein, we demonstrate substitutional doping of monolayer tungsten disulfide (WS2) with Nb via the chemical vapor deposition technique. Scanning transmission electron microscopy confirms that Nb successfully substituted the W atom in the WS2 lattice. Moreover, photoluminescence indicates a significant red shift when different concentrations of Nb are introduced, in agreement with density functional theory calculations. Electrical measurements reveal the degenerate p-type semiconductor behavior of Nb-doped WS2 field-effect transistors. The successful synthesis of p-type WS2 in this study provides a promising method to expand the electronic and photonic engineering of two-dimensional materials.