Vanadium-Doped Monolayer MoS₂with Tunable Optical Properties for Field-Effect Transistors

Substitutional doping is a promising methodology to tune the optoelectronic properties of transition metal dichalcogenides (TMDs). However, to this date, direct substitution of transition metal atoms in monolayer regime has only been demonstrated with few metal atoms. Herein monolayer (ML) molybdenum disulfide (MoS2) doped with different concentrations of vanadium(V) is successfully prepared by tuning the molar ratio of MoO3 and V2O5 powder in a chemical vapor deposition (CVD) process. Interestingly, photoluminescence (PL) intensity of the V-doped ML MoS2 with optimal ratio is four times larger than that of intrinsic MoS2. Further PL spectra fittings indicate that the exciton recombination in V-doped samples is dominant relative to the trion recombination due to the p-doping effect, which is further confirmed by the gate-dependent PL testing. It is also observed that the optical bandgap of MoS2 and the threshold voltage of as-fabricated field-effect transistors (FETs) can be tuned through controllable V doping. As a proof of concept, ML MoSe2 doped with V also exhibits enhanced PL intensity due to the p-doping effect. The successful preparation of Mo-based monolayer TMDs with controllable vanadium doping could be helpful for optical absorption-based optoelectronic applications.